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Stained glass
Stained glass
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The north rose window of the Chartres Cathedral (Chartres, France), donated by Blanche of Castile. It represents the Virgin Mary, surrounded by Biblical kings and prophets. Below is St Anne, mother of the Virgin, with four righteous leaders. The window includes the arms of France and Castile.

Stained glass refers to coloured glass as a material or art and architectural works created from it. Although it is traditionally made in flat panels and used as windows, the creations of modern stained glass artists also include three-dimensional structures and sculpture. Modern vernacular usage has often extended the term "stained glass" to include domestic lead light and objets d'art created from glasswork, for example in the famous lamps of Louis Comfort Tiffany.

As a material stained glass is glass that has been coloured by adding metallic salts during its manufacture. It may then be further decorated in various ways. The coloured glass may be crafted into a stained-glass window, say, in which small pieces of glass are arranged to form patterns or pictures, held together (traditionally) by strips of lead, called cames or calms, and supported by a rigid frame. Painted details and yellow-coloured silver stain are often used to enhance the design. The term stained glass is also applied to enamelled glass in which the colors have been painted onto the glass and then fused to the glass in a kiln.

Stained glass, as an art and a craft, requires the artistic skill to conceive an appropriate and workable design, and the engineering skills to assemble the piece. A window must fit snugly into the space for which it is made, must resist wind and rain, and also, especially in the larger windows, must support its own weight. Many large windows have withstood the test of time and remained substantially intact since the Late Middle Ages. In Western Europe, together with illuminated manuscripts, they constitute a major form of medieval visual art to have survived. In this context, the purpose of a stained glass window is not to allow those within a building to see the world outside or even primarily to admit light but rather to control it. For this reason stained-glass windows have been described as "illuminated wall decorations".

The design of a window may be abstract or figurative; may incorporate narratives drawn from the Bible, history, or literature; may represent saints or patrons, or use symbolic motifs, in particular armorial. Windows within a building may be thematic, for example: within a church – episodes from the life of Christ; within a parliament building – shields of the constituencies; within a college hall – figures representing the arts and sciences; or within a home – flora, fauna, or landscape.

Glass production

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During the late medieval period, glass factories were set up where there was a ready supply of silica, the essential material for glass manufacture. Silica requires a very high temperature to melt, something not all glass factories were able to achieve. Such materials as potash, soda, and lead can be added to lower the melting temperature. Other substances, such as lime, are added to make the glass more stable. Glass is coloured by adding metallic oxide powders or finely divided metals while it is in a molten state.[1] Copper oxides produce green or bluish green, cobalt makes deep blue, and gold produces wine red and violet glass. Much of modern red glass is produced using copper, which is less expensive than gold and gives a brighter, more vermilion shade of red. Glass coloured while in the clay pot in the furnace is known as pot metal glass, as opposed to flashed glass.

Cylinder or mouth-blown ('muff') glass

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Using a blow-pipe, a glass maker will gather a glob of molten glass that was taken from the pot heating in the furnace. The 'gather' is formed to the correct shape and a bubble of air blown into it. Using metal tools, molds of wood that have been soaking in water, and gravity, the gather is manipulated to form a long, cylindrical shape. As it cools, it is reheated so that the manipulation can continue. During the process, the bottom of the cylinder is removed. Once brought to the desired size it is left to cool. One side of the cylinder is opened, and the cylinder is then put into another oven to quickly heat and flatten it, and then placed in an annealer to cool at a controlled rate, making the material more stable. "Hand-blown" or "mouth-blown" cylinder (also called muff glass) and crown glass were the types used in the traditional fabrication of stained-glass windows.

Crown glass

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Crown glass is hand-blown glass created by blowing a bubble of air into a gather of molten glass and then spinning it, either by hand or on a table that revolves rapidly like a potter's wheel. The centrifugal force causes the molten bubble to open up and flatten. It can then be cut into small sheets. Glass formed this way can be either coloured and used for stained-glass windows, or uncoloured as seen in small paned windows in 16th- and 17th-century houses. Concentric, curving waves are characteristic of the process. The centre of each piece of glass, known as the "bull's-eye", is subject to less acceleration during spinning, so it remains thicker than the rest of the sheet. It also has the pontil mark, a distinctive lump of glass left by the "pontil" rod, which holds the glass as it is spun out. This lumpy, refractive quality means the bulls-eyes are less transparent, but they have still been used for windows, both domestic and ecclesiastical. Crown glass is still made today, but not on a large scale.

Rolled glass

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Rolled glass (sometimes called "table glass") is produced by pouring molten glass onto a metal or graphite table and immediately rolling it into a sheet using a large metal cylinder, similar to rolling out a pie crust. The rolling can be done by hand or by machine. Glass can be "double rolled", which means it is passed through two cylinders at once (similar to the clothes wringers on older washing machines) to yield glass of a specified thickness (typically about 1/8" or 3mm). The glass is then annealed. Rolled glass was first commercially produced around the mid-1830s and is widely used today. It is often called cathedral glass, but this has nothing to do with medieval cathedrals, where the glass used was hand-blown.

Flashed glass

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Architectural glass must be at least 1/8 of an inch (3 mm) thick to survive the push and pull of typical wind loads. However, in the creation of red glass, the colouring ingredients must be of a certain concentration, or the colour will not develop. This results in a colour so intense that at the thickness of 1/8 inch (3 mm), the red glass transmits little light and appears black. The method employed to create red stained glass is to laminate a thin layer of red glass to a thicker body of glass that is clear or lightly tinted, forming "flashed glass".

A lightly coloured molten gather is dipped into a pot of molten red glass, which is then blown into a sheet of laminated glass using either the cylinder (muff) or the crown technique described above. Once this method was found for making red glass, other colours were made this way as well. A great advantage is that the double-layered glass can be engraved or abraded to reveal the clear or tinted glass below. The method allows rich detailing and patterns to be achieved without needing to add more lead-lines, giving artists greater freedom in their designs. A number of artists have embraced the possibilities flashed glass gives them. For instance, 16th-century heraldic windows relied heavily on a variety of flashed colours for their intricate crests and creatures. In the medieval period the glass was abraded; later, hydrofluoric acid was used to remove the flash in a chemical reaction (a very dangerous technique), and in the 19th century sandblasting started to be used for this purpose.

Islamic civilization played a major role in inspiring the art of stained glass from the 8th century onward. Mosques, homes, and cities were transformed into beautiful spaces decorated with glass. Beauty and function were essential elements of design in Islamic civilization. Perhaps in an effort to supply thousands of mosques, but also thanks to the input provided by thriving scientific activity in fields such as optics and chemistry, Islamic glassmakers transformed what had previously been a craft into Islamic stained glass, an industry employing new technologies and a large workforce from across Islamic civilization.

Across Islamic civilization, glass vessels were mass-produced from the 8th century onwards, either by blowing liquid glass in chambers or by cutting it from crystal. Glassmakers in Syria, and to a lesser extent Egypt, inherited and improved upon this glassmaking technique, developing their own techniques for mastering the art of Islamic stained glass, its coloring, and its decoration, expanding the variety of products.

The history of stained glass in Syria dates back to ancient times, as Syria was influenced by successive civilizations, such as the Roman and Byzantine. Syrian stained glass is characterized by its intricate geometric and floral designs, reflecting the skill of Syrian artisans.

There are a number of glass factories, particularly in Germany, the United States, England, France, Poland, Russia, and Syria, which produce high-quality glass, both hand-blown (cylinder, disc, and crown) and rolled (cathedral and opalescent). Contemporary stained glass artists have a number of resources to draw on in their work for centuries from other artists, from whom they learn, continuing the tradition in new ways. In the late 19th and 20th centuries, there were many innovations in techniques and types of glass used. Many new types of glass were developed for use in stained glass windows, notably Tiffany glass and stained glass panels.

Techniques

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"Pot metal" and flashed glass

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The primary method of including colour in stained glass is to use glass, originally colourless, that has been given colouring by mixing with metal oxides in its melted state (in a crucible or "pot"), producing glass sheets that are coloured all the way through; these are known as "pot metal" glass.[2] A second method, sometimes used in some areas of windows, is flashed glass, a thin coating of coloured glass fused to colourless glass (or coloured glass, to produce a different colour). In medieval glass flashing was especially used for reds, as glass made with gold compounds was very expensive and tended to be too deep in colour to use at full thickness.[3]

Glass paint

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Grisaille stained glass (15th century)

Another group of techniques give additional colouring, including lines and shading, by treating the surfaces of the coloured sheets, and often fixing these effects by a light firing in a furnace or kiln. These methods may be used over broad areas, especially with silver stain, which gave better yellows than other methods in the Middle Ages. Alternatively they may be used for painting linear effects, or polychrome areas of detail. The most common method of adding the black linear painting necessary to define stained glass images is the use of what is variously called "glass paint", "vitreous paint", or "grisaille paint". This was applied as a mixture of powdered glass, iron or rust filings to give a black colour, clay, and oil, vinegar or water for a brushable texture, with a binder such as gum arabic. This was painted on the pieces of coloured glass, and then fired to burn away the ingredients giving texture, leaving a layer of the glass and colouring, fused to the main glass piece.[4]

Silver stain

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This panel of a window from a parish church in Le Mesnil-Villeman uses "silver stain" in an already masterly fashion and is in its inscription dated to the year 1313, making it the earliest dated window using this technique.[5][6][7]

"Silver stain", introduced soon after 1300, produced a wide range of yellow to orange colours; this is the "stain" in the term "stained glass". Silver compounds (notably silver nitrate)[8] are mixed with binding substances, applied to the surface of glass, and then fired in a furnace or kiln.[9] They can produce a range of colours from orange-red to yellow. Used on blue glass they produce greens. The way the glass is heated and cooled can significantly affect the colours produced by these compounds. The chemistry involved is complex and not well understood. The chemicals actually penetrate the glass they are added to a little way, and the technique therefore gives extremely stable results. By the 15th century it had become cheaper than using pot metal glass and was often used with glass paint as the only colour on transparent glass.[10] Silver stain was applied to the opposite face of the glass to silver paint, as the two techniques did not work well one on top of the other. The stain was usually on the exterior face, where it appears to have given the glass some protection against weathering, although this can also be true for paint. They were also probably fired separately, the stain needing a lower heat than the paint.[11]

"Sanguine" or "Cousin's rose"

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"Sanguine", "carnation", "Rouge Jean Cousin" or "Cousin's rose", after its supposed inventor,[12] is an iron-based fired paint producing red colours, mainly used to highlight small areas, often on flesh. It was introduced around 1500.[13] Copper stain, similar to silver stain but using copper compounds, also produced reds, and was mainly used in the 18th and 19th centuries.[14]

Cold painting

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"Cold paint" is various types of paint that were applied without firing. Contrary to the optimistic claims of the 12th century writer Theophilus Presbyter, cold paint is not very durable, and very little medieval paint has survived.[14]

Scratching techniques

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As well as painting, scratched sgraffito techniques were often used. This involved painting a colour over pot metal glass of another colour, and then before firing selectively scratching the glass paint away to make the design, or the lettering of an inscription. This was the most common method of making inscriptions in early medieval glass, giving white or light letters on a black background, with later inscriptions more often using black painted letters on a transparent glass background.[15]

"Pot glass" colours

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These are the colours in which the glass itself is made, as opposed to colours applied to the glass.

Transparent glass

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Ordinary soda-lime glass appears colourless to the naked eye when it is thin, although iron oxide impurities produce a green tint which becomes evident in thick pieces or with the aid of scientific instruments. A number of additives are used to reduce the green tint, particularly if the glass is to be used for plain window glass, rather than stained-glass windows. These additives include manganese dioxide which produces sodium permanganate, and may result in a slightly mauve tint, characteristic of the glass in older houses in New England. Selenium has been used for the same purpose.[17]

Green glass

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While very pale green is the typical colour of transparent glass, deeper greens can be achieved by the addition of Iron(II) oxide which results in a bluish-green glass. Together with chromium it gives glass of a richer green colour, typical of the glass used to make wine bottles. The addition of chromium yields dark green glass, suitable for flashed glass.[18] Together with tin oxide[clarification needed] and arsenic it yields emerald green glass.

Blue glass

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  • In medieval times, blue glass was made by adding cobalt blue, which at a concentration of 0.025% to 0.1% in soda-lime glass achieves the brilliant blue characteristic of Chartres Cathedral.
  • The addition of sulphur to boron-rich borosilicate glasses imparts a blue colour.
  • The addition of copper oxide at 2–3% produces a turquoise colour.
  • The addition of nickel, at different concentrations, produces blue, violet, or black glass.[19]

Red glass

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  • Metallic gold, in very low concentrations (around 0.001%), produces a rich ruby-coloured glass ("ruby gold"); in even lower concentrations it produces a less intense red, often marketed as "cranberry glass". The colour is caused by the size and dispersion of gold particles. Ruby gold glass is usually made of lead glass with tin added.
  • Pure metallic copper produces a very dark red, opaque glass. Glass created in this manner is generally "flashed" (laminated glass). It was used extensively in the late 19th and early 20th centuries and exploited for the decorative effects that could be achieved by sanding and engraving.
  • Selenium is an important agent to make pink and red glass. When used together with cadmium sulphide, it yields a brilliant red colour known as "Selenium Ruby".[17]

Yellow glass

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  • This was very often achieved by "silver stain" applied externally to the sheets of glass (see above).
  • The addition of sulphur, together with carbon and iron salts, is used to form iron polysulphides and produce amber glass ranging from yellowish to almost black. With calcium it yields a deep yellow colour.[20]
  • Adding titanium produces yellowish-brown glass. Titanium is rarely used on its own and is more often employed to intensify and brighten other additives.
  • Cadmium together with sulphur results in deep yellow colour, often used in glazes. However, cadmium is toxic.
  • Uranium (0.1% to 2%) can be added to give glass a fluorescent yellow or green colour.[21] Uranium glass is typically not radioactive enough to be dangerous, but if ground into a powder, such as by polishing with sandpaper, and inhaled, it can be carcinogenic. When used with lead glass with a very high proportion of lead, it produces a deep red colour.

Purple glass

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  • The addition of manganese gives an amethyst colour. Manganese is one of the oldest glass additives, and purple manganese glass has been used since early Egyptian history.
  • Nickel, depending on the concentration, produces blue, or violet, or even black glass.[19] Lead crystal with added nickel acquires a purplish colour.

White glass

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Creating stained-glass windows

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Swiss armorial glass of the Arms of Unterwalden, 1564, with typical painted details, extensive silver stain, Cousin's rose on the face, and flashed ruby glass with abraded white motif.

Design

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The first stage in the production of a window is to make, or acquire from the architect or owners of the building, an accurate template of the window opening that the glass is to fit.

The subject matter of the window is determined to suit the location, a particular theme, or the wishes of the patron. A small design called a Vidimus (from Latin "we have seen") is prepared which can be shown to the patron. A scaled model maquette may also be provided. The designer must take into account the design, the structure of the window, the nature and size of the glass available and his or her own preferred technique.

A traditional narrative window has panels which relate a story. A figurative window could have rows of saints or dignitaries. Scriptural texts or mottoes are sometimes included and perhaps the names of the patrons or the person to whose memory the window is dedicated. In a window of a traditional type, it is usually left to the discretion of the designer to fill the surrounding areas with borders, floral motifs and canopies.

A full-sized cartoon is drawn for every "light" (opening) of the window. A small church window might typically have two lights, with some simple tracery lights above. A large window might have four or five lights. The east or west window of a large cathedral might have seven lights in three tiers, with elaborate tracery. In medieval times the cartoon was drawn directly on the surface of a whitewashed table, which was then used as a pattern for cutting, painting and assembling the window. The cartoon is then divided into a patchwork, providing a template for each small glass piece. The exact position of the lead which holds the glass in place is also noted, as it is part of the calculated visual effect.

Selecting and painting the glass

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Each piece of glass is selected for the desired colour and cut to match a section of the template. An exact fit is ensured by "grozing" the edges with a tool which can nibble off small pieces. Details of faces, hair and hands can be painted onto the inner surface of the glass using a special glass paint which contains finely ground lead or copper filings, ground glass, gum arabic and a medium such as wine, vinegar or (traditionally) urine. The art of painting details became increasingly elaborate and reached its height in the early 20th century.

From 1300 onwards, artists started using "silver stain" which was made with silver nitrate. It gave a yellow effect ranging from pale lemon to deep orange. It was usually painted onto the outside of a piece of glass, then fired to make it permanent. This yellow was particularly useful for enhancing borders, canopies and haloes, and turning blue glass into green glass. By about 1450, a stain known as "Cousin's rose" was used to enhance flesh tones.

In the 16th century, a range of glass stains were introduced, most of them coloured by ground glass particles. They were a form of enamelled glass. Painting on glass with these stains was initially used for small heraldic designs and other details. By the 17th century a style of stained glass had evolved that was no longer dependent upon the skilful cutting of coloured glass into sections. Scenes were painted onto glass panels of square format, like tiles. The colours were then annealed to the glass before the pieces were assembled.

A method used for embellishment and gilding is the decoration of one side of each of two pieces of thin glass, which are then placed back to back within the lead came. This allows for the use of techniques such as Angel gilding and Églomisé to produce an effect visible from both sides but not exposing the decorated surface to the atmosphere or mechanical damage.

Assembly and mounting

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Once the glass is cut and painted, the pieces are assembled by slotting them into H-sectioned lead cames. All the joints are then soldered together and the glass pieces are prevented from rattling and the window made weatherproof by forcing a soft oily cement or mastic between the glass and the cames. In modern windows, copper foil is now sometimes used instead of lead.[22] For further technical details, see Came glasswork.

Traditionally, when a window was inserted into the window space, iron rods were put across it at various points to support its weight. The window was tied to these rods with lead strips or, more recently, with copper wires. Some very large early Gothic windows are divided into sections by heavy metal frames called ferramenta. This method of support was also favoured for large, usually painted, windows of the Baroque period.

History

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Origins

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Coloured glass has been produced since ancient times. Both the Egyptians and the Romans excelled at the manufacture of small colored glass objects. Phoenicia was important in glass manufacture with its chief centres Sidon, Tyre and Antioch. The British Museum holds two of the finest Roman pieces, the Lycurgus Cup, which is a murky mustard color but glows purple-red to transmitted light, and the cameo glass Portland vase which is midnight blue, with a carved white overlay.

In early Christian churches of the 4th and 5th centuries, there are many remaining windows which are filled with ornate patterns of thinly sliced alabaster set into wooden frames, giving a stained-glass like effect.[23][24]

Evidence of stained-glass windows in churches and monasteries in Britain can be found as early as the 7th century. The earliest known reference dates from 675 AD when Benedict Biscop imported workmen from France to glaze the windows of the monastery of St Peter which he was building at Monkwearmouth. Hundreds of pieces of coloured glass and lead, dating back to the late 7th century, have been discovered here and at Jarrow.[25][26]

In the Middle East, the glass industry of Syria continued during the Islamic period with major centres of manufacture at Raqqa, Aleppo and Damascus and the most important products being highly transparent colourless glass and gilded glass, rather than coloured glass.[27][28]

In Southwest Asia

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The creation of stained glass in Southwest Asia began in ancient times. One of the region's earliest surviving formulations for the production of colored glass comes from the Assyrian city of Nineveh, dating to the 7th-century BC. The Kitab al-Durra al-Maknuna, attributed to the 8th century alchemist Jābir ibn Hayyān, discusses the production of colored glass in ancient Babylon and Egypt. The Kitab al-Durra al-Maknuna also describes how to create colored glass and artificial gemstones made from high-quality stained glass.[29] The tradition of stained glass manufacture has continued, with mosques, palaces, and public spaces being decorated with stained glass throughout the Islamic world. The stained glass of Islam is generally non-pictorial and of purely geometric design, but may contain both floral motifs and text.

Stained glass creation had flourished in Persia (now Iran) during the Safavid dynasty (1501–1736 A.D.), and Zand dynasty (1751–1794 A.D.).[30] In Persia stained glass sash windows are called Orosi windows (or transliterated as Arasi, and Orsi), and were once used for decoration, as well as controlling the incoming sunlight in the hot and semi-arid climate.[30][31]

Medieval glass in Europe

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Stained glass, as an art form, reached its height in the Middle Ages when it became a major pictorial form used to illustrate the narratives of the Bible to a largely illiterate populace.

In the Romanesque and Early Gothic period, from about 950 to 1240, the untraceried windows demanded large expanses of glass which of necessity were supported by robust iron frames, such as may be seen at Chartres Cathedral and at the eastern end of Canterbury Cathedral. As Gothic architecture developed into a more ornate form, windows grew larger, affording greater illumination to the interiors, but were divided into sections by vertical shafts and tracery of stone. This elaboration of form reached its height of complexity in the Flamboyant style in Europe, and windows grew still larger with the development of the Perpendicular style in England and Rayonnant style in France.

Integrated with the lofty verticals of Gothic cathedrals and parish churches, glass designs became more daring. The circular form, or rose window, developed in France from relatively simple windows with openings pierced through slabs of thin stone to wheel windows, as exemplified by the west front of Chartres Cathedral, and ultimately to designs of enormous complexity, the tracery being drafted from hundreds of different points, such as those at Sainte-Chapelle, Paris and the "Bishop's Eye" at Lincoln Cathedral.

While stained glass was widely manufactured, Chartres was the greatest centre of stained glass manufacture, producing glass of unrivalled quality.[32]

Renaissance, Reformation and Classical windows

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Probably the earliest scheme of stained-glass windows that was created during the Renaissance was that for Florence Cathedral, devised by Lorenzo Ghiberti.[34] The scheme includes three ocular windows for the dome and three for the facade which were designed from 1405 to 1445 by several of the most renowned artists of this period: Ghiberti, Donatello, Uccello and Andrea del Castagno. Each major ocular window contains a single picture drawn from the Life of Christ or the Life of the Virgin Mary, surrounded by a wide floral border, with two smaller facade windows by Ghiberti showing the martyred deacons, St Stephen and St Lawrence. One of the cupola windows has since been lost, and that by Donatello has lost nearly all of its painted details.[34]

In Europe, stained glass continued to be produced; the style evolved from the Gothic to the Classical, which is well represented in Germany, Belgium and the Netherlands, despite the rise of Protestantism. In France, much glass of this period was produced at the Limoges factory, and in Italy at Murano, where stained glass and faceted lead crystal are often coupled together in the same window. The French Revolution brought about the neglect or destruction of many windows in France. Nonetheless, the country still holds the largest set of Renaissance stained glass in its churches, particularly in the regions of Normandy and Champagne where there were vivid ateliers in many cities until the early 17th century with the stained glass painter Linard Gonthier being active in Troyes until 1642. There are 1042 preserved 16th-century windows in the Aube department alone.[35]

At the Reformation in England, large numbers of medieval and Renaissance windows were smashed and replaced with plain glass. The Dissolution of the Monasteries under Henry VIII and the injunctions of Thomas Cromwell against "abused images" (the object of veneration) resulted in the loss of thousands of windows. Few remain undamaged; of these the windows in the private chapel at Hengrave Hall in Suffolk are among the finest. With the latter wave of destruction the traditional methods of working with stained glass died, and were not rediscovered in England until the early 19th century. See Stained glass – British glass, 1811–1918 for more details.

In the Netherlands a rare scheme of glass has remained intact at Grote Sint-Jan Church, Gouda. The windows, some of which are 18 metres (59 feet) high, date from 1555 to the early 1600s; the earliest is the work of Dirck Crabeth and his brother Wouter. Many of the original cartoons still exist.[36]

In Latin America

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Stained glass was first imported to Latin America during the 17th–18th centuries by Portuguese and Spanish settlers. By the 20th century, many European artists had begun to establish their own studios within Latin America and had started up local production. With these new local studios came inventive techniques and less traditional imagery.[37] Examples of these more modern works of art are the Basílica Nuestra Señora de Lourde and the Templo Vótivo de Maipú both located in Chile.

Revival in Great Britain and Ireland

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The Catholic revival in England, gaining force in the early 19th century with its renewed interest in the medieval church, brought a revival of church building in the Gothic style, claimed by John Ruskin to be "the true Catholic style". The architectural movement was led by Augustus Welby Pugin. Many new churches were planted in large towns and many old churches were restored. This brought about a great demand for the revival of the art of stained-glass window making.

Among the earliest 19th-century English manufacturers and designers were William Warrington and John Hardman of Birmingham, whose nephew, John Hardman Powell, had a commercial eye and exhibited works at the Philadelphia Exhibition of 1876, influencing stained glass in the United States of America. Other manufacturers included William Wailes, Ward and Hughes, Clayton and Bell, Heaton, Butler and Bayne and Charles Eamer Kempe. A Scottish designer, Daniel Cottier, opened firms in Australia and the US.

Revival in France

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In France there was a greater continuity of stained glass production than in England. In the early 19th century most stained glass was made of large panes that were extensively painted and fired, the designs often being copied directly from oil paintings by famous artists. In 1824 the Sèvres porcelain factory began producing stained glass to supply the increasing demand. In France many churches and cathedrals suffered despoliation during the French Revolution. During the 19th century a great number of churches were restored by Viollet-le-Duc. Many of France's finest ancient windows were restored at that time. From 1839 onwards much stained glass was produced that very closely imitated medieval glass, both in the artwork and in the nature of the glass itself. The pioneers were Henri Gèrente and André Lusson.[38] Other glass was designed in a more Classical manner, and characterised by the brilliant cerulean colour of the blue backgrounds (as against the purple-blue of the glass of Chartres) and the use of pink and mauve glass.

Revival in Germany, Austria and beyond

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During the mid- to late 19th century, many of Germany's ancient buildings were restored, and some, such as Cologne Cathedral, were completed in the medieval style. There was a great demand for stained glass. The designs for many windows were based directly on the work of famous engravers such as Albrecht Dürer. Original designs often imitate this style. Much 19th-century German glass has large sections of painted detail rather than outlines and details dependent on the lead. The Royal Bavarian Glass Painting Studio was founded by Ludwig I in 1827.[38] A major firm was Mayer of Munich, which commenced glass production in 1860, and is still operating as Franz Mayer of Munich, Inc.. German stained glass found a market across Europe, in America and Australia. Stained glass studios were also founded in Italy and Belgium at this time.[38]

In the Austrian Empire and later Austria-Hungary, one of the leading stained glass artists was Carl Geyling, who founded his studio in 1841. His son would continue the tradition as Carl Geyling's Erben, which still exists today. Carl Geyling's Erben completed numerous stained-glass windows for major churches in Vienna and elsewhere, and received an imperial and royal warrant of appointment from emperor Franz Joseph I of Austria.

Innovations in Britain and Europe

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Among the most innovative English designers were the Pre-Raphaelites, William Morris (1834–1898) and Edward Burne-Jones (1833–1898), whose work heralds the influential Arts and Crafts Movement, which regenerated stained glass throughout the English-speaking world. Amongst its most important exponents in England was Christopher Whall (1849–1924), author of the classic craft manual 'Stained Glass Work' (published London and New York, 1905), who advocated the direct involvement of designers in the making of their windows. His masterpiece is the series of windows (1898–1910) in the Lady Chapel at Gloucester Cathedral. Whall taught at London's Royal College of Art and Central School of Arts and Crafts: his many pupils and followers included Karl Parsons, Mary Lowndes, Henry Payne, Caroline Townshend, Veronica Whall (his daughter) and Paul Woodroffe.[39] The Scottish artist Douglas Strachan (1875–1950), who was much influenced by Whall's example, developed the Arts & Crafts idiom in an expressionist manner, in which powerful imagery and meticulous technique are masterfully combined. In Ireland, a generation of young artists taught by Whall's pupil Alfred Child at Dublin's Metropolitan School of Art created a distinctive national school of stained glass: its leading representatives were Wilhelmina Geddes, Michael Healy and Harry Clarke.

Art Nouveau or Belle Époque stained glass design flourished in France, and Eastern Europe, where it can be identified by the use of curving, sinuous lines in the lead, and swirling motifs. In France it is seen in the work of Francis Chigot of Limoges. In Britain it appears in the refined and formal leadlight designs of Charles Rennie Mackintosh.

Innovations in the United States

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J&R Lamb Studios, established in 1857 in New York City, was the first major decorative arts studio in the United States and for many years a major producer of ecclesiastical stained glass.

Notable American practitioners include John La Farge (1835–1910), who invented opalescent glass and for which he received a U.S. patent on 24 February 1880, and Louis Comfort Tiffany (1848–1933), who received several patents for variations of the same opalescent process in November of the same year and he used the copper foil method as an alternative to lead in some windows, lamps and other decorations. Sanford Bray of Boston patented the use of copper foil in stained glass in 1886,[40] However, a reaction against the aesthetics and technique of opalescent windows - led initially by architects such as Ralph Adams Cram - led to a rediscovery of traditional stained glass in the early 1900s. Charles J. Connick (1875–1945), who founded his Boston studio in 1913, was profoundly influenced by his study of medieval stained glass in Europe and by the Arts & Crafts philosophy of Englishman Christopher Whall. Connick created hundreds of windows throughout the US, including major glazing schemes at Princeton University Chapel (1927–29) and at Pittsburgh's Heinz Memorial Chapel (1937–38).[39] Other American artist-makers who espoused a medieval-inspired idiom included Nicola D'Ascenzo of Philadelphia, Wilbur Burnham and Reynolds, Francis & Rohnstock of Boston and Henry Wynd Young and J. Gordon Guthrie of New York.

20th and 21st centuries

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Many 19th-century firms failed early in the 20th century as the Gothic movement was superseded by newer styles. At the same time there were also some interesting developments where stained glass artists took studios in shared facilities. Examples include the Glass House in London, set up by Mary Lowndes and Alfred J. Drury and An Túr Gloine in Dublin, which was run by Sarah Purser and included artists such as Harry Clarke.

A revival occurred in the middle of the century because of a desire to restore thousands of church windows throughout Europe destroyed as a result of World War II bombing. German artists led the way. Much work of the period is mundane and often was not made by its designers, but industrially produced.

Other artists sought to transform an ancient art form into a contemporary one, sometimes using traditional techniques while exploiting the medium of glass in innovative ways and in combination with different materials. The use of slab glass, a technique known as dalle de verre, where the glass is set in concrete or epoxy resin, was a 20th-century innovation credited to Jean Gaudin and brought to the UK by Pierre Fourmaintraux.[citation needed] One of the most prolific glass artists using this technique was the Benedictine monk Dom Charles Norris OSB of Buckfast Abbey.

Gemmail, a technique developed by the French artist Jean Crotti in 1936 and perfected in the 1950s, is a type of stained glass where adjacent pieces of glass are overlapped without using lead cames to join the pieces, allowing for greater diversity and subtlety of colour.[41][42] Many famous works by late 19th- and early 20th-century painters, notably Picasso, have been reproduced in gemmail.[43] A major exponent of this technique is the German artist Walter Womacka.

Among the early well-known 20th-century artists who experimented with stained glass as an abstract art form were Theo van Doesburg and Piet Mondrian. In the 1960s and 1970s, the Expressionist painter Marc Chagall produced designs for many stained-glass windows that are intensely coloured and crammed with symbolic details. Important 20th-century stained glass artists include John Hayward, Douglas Strachan, Ervin Bossanyi, Louis Davis, Wilhelmina Geddes, Karl Parsons, John Piper, Patrick Reyntiens, Johannes Schreiter, Brian Clarke, Paul Woodroffe, Jean René Bazaine at Saint Séverin, Sergio de Castro at Couvrechef- La Folie (Caen), Hamburg-Dulsberg and Romont (Switzerland), and the Loire Studio of Gabriel Loire at Chartres. The west windows of England's Manchester Cathedral, by Tony Hollaway, are some of the most notable examples of symbolic work.

In Germany, stained glass development continued with the inter-war work of Johan Thorn Prikker and Josef Albers, and the post-war achievements of Georg Meistermann, Joachim Klos, Johannes Schreiter and Ludwig Schaffrath. This group of artists, who advanced the medium through the abandonment of figurative designs and painting on glass in favour of a mix of biomorphic and rigorously geometric abstraction, and the calligraphic non-functional use of leads,[44] are described as having produced "the first authentic school of stained glass since the Middle Ages".[45] The works of Ludwig Schaffrath demonstrate the late 20th-century trends in the use of stained glass for architectural purposes, filling entire walls with coloured and textured glass. In the 1970s young British stained-glass artists such as Brian Clarke were influenced by the large scale and abstraction in German twentieth-century glass.[44]

In the UK, the professional organisation for stained glass artists has been the British Society of Master Glass Painters, founded in 1921. Since 1924 the BSMGP has published an annual journal, The Journal of Stained Glass. It continues to be Britain's only organisation devoted exclusively to the art and craft of stained glass. From the outset, its chief objectives have been to promote and encourage high standards in stained glass painting and staining, to act as a locus for the exchange of information and ideas within the stained glass craft and to preserve the invaluable stained glass heritage of Britain. See www.bsmgp.org.uk for a range of stained glass lectures, conferences, tours, portfolios of recent stained glass commissions by members, and information on courses and the conservation of stained glass. Back issues of The Journal of Stained Glass are listed and there is a searchable index for stained glass articles, an invaluable resource for stained glass researchers.

After the First World War, stained-glass window memorials were a popular choice among wealthier families. Examples can be found in churches across the UK.

In the United States, there is a 100-year-old trade organization, The Stained Glass Association of America, whose purpose is to function as a publicly recognized organization to assure survival of the craft by offering guidelines, instruction and training to craftspersons. The SGAA also sees its role as defending and protecting its craft against regulations that might restrict its freedom as an architectural art form. The current president is Kathy Bernard. Today there are academic establishments that teach the traditional skills. One of these is Florida State University's Master Craftsman Program, which recently completed a 30 ft (9.1 m) high stained-glass windows, designed by Robert Bischoff, the program's director, and Jo Ann, his wife and installed to overlook Bobby Bowden Field at Doak Campbell Stadium. The Roots of Knowledge installation at Utah Valley University in Orem, Utah is 200 feet (61 m) long and has been compared to those in several European cathedrals, including the Cologne Cathedral in Germany, Sainte-Chapelle in France, and York Minster in England.[46] There are also contemporary stained glass artists in the US who are creating stained-glass windows based on grids, rather than recognizable images.[47]

Combining ancient and modern traditions

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Buildings incorporating stained-glass windows

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Churches

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stained-glass windows were commonly used in churches for decorative and informative purposes. Many windows are donated to churches by members of the congregation as memorials of loved ones. For more on the use of stained glass to depict religious subjects, see Poor Man's Bible.

Synagogues

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In addition to Christian churches, stained-glass windows have been incorporated into Jewish temple architecture for centuries. Jewish communities in the United States saw this emergence in the mid-19th century, with such notable examples as the sanctuary depiction of the Ten Commandments in New York's Congregation Anshi Chesed. From the mid-20th century to the present, stained-glass windows have been a ubiquitous feature of American synagogue architecture. Styles and themes for synagogue stained glass artwork are as diverse as their church counterparts. As with churches, synagogue stained-glass windows are often dedicated by member families in exchange for major financial contributions to the institution.

Places of worship

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Mausolea

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Mausolea, whether for general community use or for private family use, may employ stained glass as a comforting entry for natural light, for memorialization, or for display of religious imagery.

Houses

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Stained glass windows in houses were particularly popular in the Victorian era and many domestic examples survive from this time. In their simplest form they typically depict birds and flowers in small panels, often surrounded with machine-made cathedral glass which, despite what the name suggests, is pale-coloured and textured. Many houses of the 19th and early 20th centuries feature original leadlight windows, another popular form of window glass in domestic settings.

Public and commercial buildings

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Stained glass has often been used as a decorative element in public buildings, initially in places of learning, government or justice but increasingly in other public and commercial places such as banks, retailers and railway stations. Public houses in some countries make extensive use of stained glass and leaded lights to create a comfortable atmosphere and retain privacy.

Sculpture

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See also

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References

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Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
Stained glass is a decorative form consisting of colored and painted assembled into windows or panels, where passes through to produce vibrant, illuminated designs often depicting religious scenes, narratives, or abstract patterns. The technique involves cutting pieces of —typically "" tinted by metallic oxides during manufacturing—and joining them with lead strips or foil, sometimes enhanced by vitreous paints fired onto the surface for details. This method creates a mosaic-like effect that transforms natural or artificial into a dynamic visual experience, distinguishing stained glass from other glazing forms. The techniques for producing colored glass originated in ancient civilizations, including those in the and the , but the art form of stained glass windows developed in over 1,000 years ago, with the earliest known examples from the in churches. It evolved into a major art form by the for religious purposes, particularly in Gothic cathedrals where it served as "illuminated scripture" for illiterate congregations. The medium reached its zenith between 1150 and 1500, with elaborate windows adorning structures like , symbolizing and theological concepts through biblical imagery and symbolic colors. Beyond ecclesiastical settings, stained glass later appeared in secular architecture, homes, and modern installations, adapting to styles from to contemporary abstraction. Key techniques include the production of colored glass by incorporating metal oxides such as copper for greens and reds or cobalt for blues into molten silica, resulting in translucent sheets known as cathedral or opalescent glass. Artists sketch designs, trace them onto glass using a grease pencil, cut shapes with a wheel or diamond, and apply enamel paints made of ground glass and fluxes, which are then fired at high temperatures to fuse permanently. Assembly uses lead cames—H-shaped strips soldered at intersections—to frame pieces, ensuring structural integrity while minimizing light obstruction, though modern methods like epoxy resin have supplemented traditional leading for larger or curved works. These processes demand precision, as glass cannot be reheated without risking distortion, and have remained fundamentally unchanged since the medieval period despite tools like the glass cutter improving efficiency.

Fundamentals

Definition and Characteristics

Stained glass is colored crafted into flat panels or windows, where pieces are cut to shape and assembled using lead strips, known as cames, to form decorative or pictorial designs that come alive when illuminated by transmitted . This form relies on the inherent properties of , such as its ability to be infused with metallic oxides during manufacture to achieve vibrant, stable colors throughout the material, distinguishing it from surface-treated alternatives. The resulting panels are typically set into iron or wooden frames for architectural integration, emphasizing visual narrative over functionality. Key characteristics of stained glass include its translucency, which allows to pass through while diffusing color to create dynamic, jewel-like effects that vary with the time of day and . The exhibits high , with many examples enduring environmental exposure for centuries due to its hard, dense composition stabilized by silica, lime, and soda. Production methods introduce natural variations in thickness—often ranging from 1/8 to 3/16 inch—and texture, such as subtle waves or bubbles in handcrafted sheets, which enhance interaction and prevent uniform opacity. These features make stained glass suitable for long-term use in buildings, where it withstands structural demands while maintaining aesthetic integrity. Unlike blown glass, which forms three-dimensional vessels or objects through shaping molten material, stained glass prioritizes flat, cut pieces assembled into two-dimensional compositions for pictorial storytelling in windows or partitions. It also differs from clear , which focuses on transparency and structural clarity without coloration or leaded assembly, as stained glass intentionally manipulates light through color and texture to evoke emotional or symbolic responses. In modern contexts, stained glass has evolved from primarily religious applications to secular uses in , , and , incorporating abstract forms and innovative materials while retaining its core light-transmitting essence.

Optical Properties and Light Interaction

Stained glass exhibits unique that govern its interaction with , primarily through the processes of , transmission, and absorption. When visible encounters the glass surface, occurs due to the material's , typically around 1.52 for soda-lime-silica compositions used in stained glass, bending the path as it enters and exits the medium. Transmission allows non-absorbed wavelengths to pass through, while absorption removes specific portions of the by exciting electrons in the glass matrix, resulting in the characteristic glow and coloration observed in windows. These interactions are fundamental to the luminous effects of stained glass, where is filtered and directed to create vibrant, ethereal illumination. Color in stained glass arises from the selective absorption of light wavelengths by impurities and metallic oxides incorporated into the glass during production. Transition metal ions, such as copper(II) for blues and greens or iron(II/III) for greens and browns, produce color through d-d electron transitions or charge transfer mechanisms that absorb particular visible wavelengths, transmitting the complementary colors. For instance, cobalt ions absorb in the red and yellow regions, yielding intense blues by transmitting shorter wavelengths. This wavelength selection is inherent to the ionic environment within the amorphous glass structure, enabling stable, integral coloration without relying on surface coatings. The thickness and texture of stained glass significantly influence , glow, and shadow formation. Thicker sections increase the path length for travel, enhancing absorption and intensifying color saturation while reducing overall transmission, which can create deeper shadows and a more dramatic glow in illuminated areas. Textured surfaces, such as those from mouth-blown methods, scatter through surface irregularities and internal imperfections like bubbles or striations, promoting that softens direct beams into a radiant, even illumination rather than harsh spots. This contributes to the ethereal quality of stained glass in architectural settings, where appears to emanate from within the . The mathematical basis for light absorption in stained glass is described by Beer's law, which quantifies how intensity decreases exponentially with path length:
A=ϵlcA = \epsilon l c
where AA is the , ϵ\epsilon is the molar absorptivity (specific to the and ), ll is the path length through the glass (related to thickness), and cc is the concentration of the absorbing species. In the of stained glass, this relationship explains color intensity; higher concentrations of metallic ions or greater thicknesses yield stronger absorption of unwanted , resulting in more vivid transmitted colors without altering the underlying .
Stained glass colors demonstrate superior stability against (UV) exposure compared to traditional pigments, as the chromophoric metal ions are embedded within the durable glass matrix, resisting over centuries. Unlike organic pigments, which fade via bond breaking under UV , the inorganic ions in stained glass maintain their electronic configurations, with minimal color shift even after prolonged exposure. This inherent resistance has preserved medieval stained glass windows in vibrant condition, underscoring the material's in light-transmitting applications.

Materials and Production

Cylinder or Mouth-Blown Glass

The cylinder or mouth-blown glass method, also referred to as the broad sheet or muff process, emerged as a key technique for producing flat glass sheets in medieval , enabling the creation of expansive panels for stained glass windows. This approach, detailed in the 12th-century treatise On Diverse Arts by the German monk Theophilus Presbyter, involved shaping molten glass through manual blowing to form cylindrical vessels that were subsequently flattened. By the , the method had become widespread across , particularly in regions like and , where it supported the production of colored glass for Gothic cathedrals. The process begins with a skilled glassblower gathering a gather of molten from a furnace onto the end of a blowpipe, a long hollow iron tube approximately 5 feet in length with a flared mouthpiece. The glassblower then blows air into the pipe to inflate the gather into a large bubble, typically 3 to 4 feet in diameter, while rotating it to maintain even thickness. To form the , the bubble's far end is attached to a punty—a solid iron rod about 4 feet long—allowing the glassblower to swing the piece horizontally or vertically, elongating the bubble into a tall, narrow up to 10 feet long and 8 to 12 inches in diameter. Once cooled sufficiently, the ends of the are cut off using heated shears, and a longitudinal score is made along its length with a hot iron or diamond scorer; the is then split open by tapping. Finally, the opened is transferred to a flattening oven, or lehr, a long annealing heated to around 500–600°C, where it is reheated and allowed to unfurl and flatten under its own weight into a sheet, often aided by wooden tools or rollers; the sheet is then slowly cooled in the lehr to relieve internal stresses and prevent cracking. Essential tools in this labor-intensive include the blowpipe for initial gathering and blowing, the punty for handling and elongating the without direct hand contact, and the annealing oven to control cooling rates—typically maintaining temperatures that decrease gradually over hours or days to avoid . This method yields large sheets measuring up to 2 by 3 feet or larger, with relatively uniform thickness and minimal optical distortion, making it ideal for assembling expansive, window-scale stained glass compositions where clarity and scale are paramount. The subtle variations in thickness inherent to the blowing process can create gentle undulations and light refractions that enhance the artistic depth of the final work. However, the technique's reliance on manual skill limits production efficiency, often requiring teams of multiple artisans and consuming significant time—up to several hours per sheet—while introducing imperfections such as air bubbles trapped during blowing and inconsistent thickness ranging from 1/16 to 1/8 inch across the surface. These characteristics, while adding character, could compromise structural integrity in larger panels if not managed carefully during annealing. In contrast to modern industrial rolled glass, mouth-blown cylinder glass provides a more textured, handmade quality prized for historical restorations. This type of glass serves as the base material for techniques, where metallic oxides are incorporated into the melt for inherent coloring.

Crown Glass

Crown glass, a traditional method of producing sheet glass for windows including stained glass applications, involves a labor-intensive hand-blowing and spinning technique that imparts distinctive optical qualities. The process begins with a glassblower using a blowpipe to create a hollow globe of molten from the furnace. This globe is then carefully transferred to a punty, a solid iron rod attached to the opposite end from the blowpipe, after which the blowpipe is removed, leaving an open hole in the glass. The assembly is reheated in the furnace to maintain pliability and spun rapidly—often at speeds exceeding 30 revolutions per minute—to the molten glass into a flat, circular disk typically 25 to 50 centimeters in diameter, though larger examples up to 1.5 meters have been recorded. Once cooled and annealed over several days to prevent cracking, the disk is scored and cut into concentric segments, yielding panes suitable for glazing. The central portion of the disk, known as the bull's-eye, remains as a thick, imperfect hub marked by the pontil scar where the punty was attached. The resulting glass exhibits unique characteristics that enhance its suitability for stained glass windows, particularly in how it interacts with . The bull's-eye center forms a pronounced, rounded imperfection that was often reserved for smaller or less prominent window sections due to its , while the surrounding panes display a subtle wavy texture from the spinning process, manifesting as concentric ripples and undulations that diffuse and play with transmitted , creating a shimmering, dynamic effect. This texture arises from minor variations in thickness—typically 1.5 to 3 millimeters—and trapped air bubbles that form widening circles, contributing to an organic, artisanal appearance absent in more uniform modern glass. In stained glass contexts, these qualities amplify the vibrancy of colored pieces by softening edges and introducing subtle refractions, evoking a of movement in . Crown glass reached its historical peak in production during the 17th and 18th centuries, particularly in and , where it became the dominant method for supplying window glass amid growing demand for architectural glazing, including in churches and cathedrals featuring stained glass. In , the technique originated around in the 1320s as a closely guarded , with exports to supporting medieval restorations before local production began in the 1670s following royal patents. English manufacturers, such as those in and , scaled up output to meet the needs of expanding urban and buildings, producing millions of panes annually by the mid-18th century. Its use in stained glass during this era is evident in surviving windows from sites like the churches of St. Martin's-in-the-Fields in , where the glass's luster complemented painted and stained elements. The decline of crown glass production accelerated in the mid-19th century, ultimately being superseded by the more efficient or mouth-blown method, which allowed for larger, flatter sheets at lower cost. The abolition of the British glass in 1845 removed economic incentives favoring the thinner crown glass—previously taxed by weight—and enabled processes to dominate, producing up to four times more per furnace cycle with reduced labor. By the , French and Belgian innovators had refined blowing for industrial scales, rendering the spinning method obsolete for most commercial applications by 1850, though limited artisanal revival persists for historical restorations.

Rolled Glass

Rolled glass, also known as table glass or cathedral glass, represents a pivotal advancement in stained glass production that originated in the during the Gothic Revival movement, enabling the creation of larger and more consistent sheets to meet the era's renewed demand for architectural glazing. This method transitioned stained glass fabrication from labor-intensive hand-blown techniques to semi-mechanized processes, supporting the widespread revival of medieval-style windows in churches and public buildings across and America. The production process begins with melting raw materials—such as silica sand, soda ash, and lime—in a furnace until they form molten at temperatures exceeding 1,400°C. The liquid is then poured onto a flat, heat-resistant table made of iron, metal, or , where it is spread and flattened using one or more rotating cylinders to form thin sheets of uniform thickness, typically 2-4 mm. After rolling, the is annealed in a to relieve internal stresses, resulting in stable sheets up to several in length that can be cut to size for stained glass assembly. variations mimic the irregular textures of earlier handcrafted by introducing deliberate imperfections during rolling, while modern iterations employ automated machinery for precision and efficiency. Key advantages of rolled glass include its consistent thickness, which minimizes distortions in light transmission and facilitates precise cutting for intricate designs, as well as its scalability for , allowing manufacturers to produce vast quantities with fewer defects like air bubbles or inconsistencies compared to manual methods. This uniformity reduces material waste and supports the creation of expansive windows, contributing to the affordability and accessibility of stained glass during the 19th and 20th centuries. Rolled glass varieties are distinguished by their textures, which influence light diffusion and in stained glass applications. Cathedral glass features a smooth or lightly textured surface, often with subtle ripples that enhance light scattering without opacity, making it ideal for vibrant, translucent panels. Antique rolled glass incorporates seeded bubbles and wavy distortions to evoke historical authenticity, while opalescent subtypes—developed in the late —blend multiple colors into a milky, iridescent matrix that softens and diffuses light dramatically, as pioneered in American innovations. These textures allow artists to achieve varied luminous qualities, from clear transmission to ethereal glows, in modern stained glass works.

Flashed Glass

Flashed glass is a type of produced by layering a thin sheet of colored molten over a thicker base of clear or lightly tinted molten glass, which are then rolled together to form a single composite sheet. This technique, often involving dipping a gather of base glass into a pot of colored glass before rolling, results in the colored layer adhering closely to the base, typically with the overall sheet thickness ranging from 1 to 3 mm and the colored overlay being much thinner, around 30 to 300 micrometers. The primary benefit of flashed glass lies in its ability to create tonal variations and within a single piece by selectively removing portions of the thin colored layer—through scratching, , or abrasion—to expose the underlying base , thereby achieving depth and gradation without the need for assembling multiple separate pieces. This method enhances artistic flexibility, allowing glaziers to produce subtle transitions in color intensity and simulate three-dimensional effects in flat panels. Historically, flashed emerged in the 13th century and was particularly significant in medieval stained glass production for achieving vibrant s, known as ruby flashing, where a thin red layer was applied over clear glass to overcome the opacity of thicker red formulations colored with or . of surviving medieval examples reveals two main micromorphological types of such flashed red glass, indicating systematic technological evolution from the 12th to 16th centuries, though early methods sometimes involved mixing weakly colored glasses rather than simple dipping. Variations of the technique include double or triple flashing, where additional layers of different colors are successively applied and rolled onto the base, enabling more complex multicolored effects and finer control over shading in intricate designs. These multilayered sheets expand the palette for advanced glazing while maintaining the core advantage of integrated layering.

Techniques

Pot Metal Glass

Pot metal glass refers to glass that is colored uniformly throughout its thickness by incorporating metallic oxides or salts into the molten batch during the melting process in a clay , or "pot," hence the name. This technique produces sheets of with consistent hue and translucency, allowing light to pass through while creating vibrant effects essential for stained glass windows. The method was particularly valued for its durability and integration with lead cames, as the bulk coloring ensured color stability without fading or peeling over time. The production process begins with the preparation of the glass batch, typically consisting of silica (from ), an alkali flux such as or to lower the , and a stabilizer like lime to enhance . Metallic oxides are added to this mixture before or during in the pot at temperatures around 1,200–1,400°C, where they dissolve and distribute evenly, imparting color without altering the 's fundamental structure. Common examples include for greens and oxide for blues, which react within the melt to form stable color compounds. Once melted, the colored is gathered on a blowpipe, blown into a cylindrical or bulbous shape, and then flattened into sheets using techniques like or blowing, resulting in irregular but usable panes. In terms of properties, glass can range from translucent to semi-opaque, depending on the concentration and glass thickness, which typically varied from 1–3 mm in medieval production to allow optimal transmission. This volumetric coloring provides a luminous when assembled in windows, as interacts directly with the embedded colorants rather than surface applications. The glass's made it suitable for secure attachment with lead strips, resisting common in thinner or surface-treated alternatives. Historically, glass dominated stained glass production in medieval from the 12th to 15th centuries, enabling the creation of expansive, vividly hued narrative windows in cathedrals such as and . The technique is detailed in the early 12th-century treatise De diversis artibus by Theophilus Presbyter, who described the melting and coloring processes as integral to ecclesiastical art, marking a shift from earlier Romanesque styles toward the brilliant Gothic aesthetic. Its use peaked during this period due to advancements in furnace technology and access to trade-route oxides, fostering the iconic blue-and-red dominated palettes of the era. A key limitation of glass is that each sheet yields only a single, fixed color, necessitating precise cutting and piecing together of multiple pieces to form complex patterns or gradients within a . This labor-intensive approach contrasted with later innovations like flashing, which layered thin colored over clear bases for multilayered effects. Despite this, the method's simplicity and reliability sustained its prevalence until the , when enamel painting began supplementing it.

Glass Painting

Glass painting is a traditional technique in stained glass production that involves applying vitreous enamels to the surface of glass pieces to create fine details, shading, and tonal variations, thereby enhancing the overall realism and narrative depth of windows. This method emerged in 14th-century , particularly in regions like and , where it allowed glaziers to introduce painterly effects such as shadows and highlights, bridging the gap between flat colored glass and more sculptural artistic representations in cathedrals and religious buildings. The materials for glass painting consist of finely ground glass powder combined with fluxes like to lower the , and pigments such as or filings to achieve dark brown or black hues in the enamel. These components are mixed into a thick paste with a binding medium, such as or , to facilitate application with specialized brushes—fine liner brushes for precise lines, flat brushes for broad washes, and brushes for textured effects. The process begins with the artist tracing or sketching details directly onto the glass using the enamel paste, often in successive layers to build : initial washes establish tones, followed by darker lines and for depth. The painted pieces are then placed in a and fired at temperatures ranging from 600 to 700°C for approximately 15 minutes, during which the enamel fuses seamlessly with the surface for permanence; multiple firings may be necessary for layered effects, with careful to avoid distortion. In practice, glass painting serves to outline facial features, drapery folds, and architectural elements in human figures, while also providing subtle modeling for flesh tones through graduated shading and toning backgrounds to harmonize with the inherent colors of the pot metal glass. This technique enables intricate detailing on otherwise boldly colored sheets, contributing to the lifelike quality of medieval and stained glass compositions.

Silver Staining

Silver staining is a chemical technique developed in the early , likely in , that allows artisans to produce yellow to orange hues on clear or lightly colored without relying on pot metal coloring. This innovation revolutionized stained glass production by enabling the depiction of flesh tones, hair, and radiant halos directly on white , expanding artistic possibilities beyond the limited palette of colored sheets available at the time. The process involves preparing a paste from silver compounds, typically or mixed with a binder such as clay, gum, or Venice turpentine, which is applied to the reverse side of the piece—the surface that will face outward in the finished . Upon firing in a at temperatures between 500°C and 650°C for several minutes, the silver ions penetrate the surface and reduce to metallic silver nanoparticles during the heating process. This reduction causes the to scatter blue light while transmitting wavelengths, resulting in the characteristic that becomes an integral part of the rather than a surface . The color range of silver staining spans from pale lemon yellow to deep or orange, with the exact shade determined by factors such as the concentration of silver in the paste, the composition and thickness of the base , and the firing and duration. Lower concentrations and higher firing temperatures tend to produce lighter yellows, while denser applications and lower temperatures yield richer, more intense tones. Artists can achieve gradations by varying application thickness or layering multiple firings, allowing for subtle modeling in designs. One key advantage of silver staining is its translucency, as the stain transmits from both sides of the , making it visible when viewed from inside or outside the building—unlike opaque paints applied to . This property ensures durability against weathering and enhances the luminous quality of stained glass windows. Additionally, it can be combined with flashed ruby glass to create crimson effects by staining the clear overlay, further broadening color options in complex compositions.

Sanguine or Cousin's Rose

The sanguine or Cousin's Rose technique is a specialized method in stained glass production for creating translucent red tones, primarily through the application of an iron-based paint to the glass surface. This approach allows for the addition of vibrant, light-transmitting reds that enhance facial details, such as cheeks and lips, in figurative windows, offering a more naturalistic and luminous effect compared to solid pot metal glass. The paint's high transparency enables light to penetrate and diffuse, producing dramatic, glowing highlights that contribute to the overall theatrical quality of the composition. It is frequently employed on flashed glass, where thin layers of color are built to achieve depth without blocking light entirely. The process begins with preparing the pigment from , typically (α-Fe₂O₃), ground into a fine powder and mixed with a of pulverized , along with a binding medium like or wine to form a paintable paste. This mixture is brushed onto the reverse side of white or flashed , then the piece is fired in a at low temperatures, generally between 600°C and 700°C, to fuse the iron particles into the via oxidation. The oxidation reaction during firing develops the characteristic ruby color, with the intensity varying based on the paint's thickness, the iron concentration, and the exact firing conditions. Historical recipes emphasize the use of natural iron sources like Crocus Martis (roasted iron ) to ensure stable adhesion and color development. Named after the 16th-century French painter Jean Cousin the Elder, the technique—also called Rouge Jean Cousin—originated in the late but gained prominence under that specific designation during 19th-century revivals of medieval stained glass practices in . It was particularly valued in the Gothic Revival movement for recreating authentic period effects in new commissions. However, the method's reliance on precise control makes it challenging; the firing process is fickle, with variations in temperature or atmosphere potentially leading to inconsistent shades from pale pink to deep brown, or even poor adhesion and peeling of the paint layer.

Cold Painting and Scratching

Cold painting refers to the application of non-vitreous paints directly onto the surface of stained glass without firing, allowing for the addition of fine details such as , inscriptions, or features. This technique typically employs materials like archival oil paints, varnishes, or modern water-based acrylics, which adhere through drying or low-temperature curing rather than fusion with the glass substrate. In contrast to fired enamels, cold painting provides a reversible option suitable for temporary enhancements or adjustments during the creative process. Scratching, or in the context of stained glass detailing, involves abrading the painted surface or the glass itself to reveal underlying layers or create textured effects. Tools such as fine needles, scribes, or etching creams are used to selectively remove material, producing highlights, patterns, or frosted textures that enhance light diffusion. This mechanical method is often applied over a base layer of to define contours or add depth without permanent chemical bonding. These techniques find primary use in stained glass repairs, where cold painting stabilizes flaking original details on fragile panels, and restores lost textures through controlled abrasion. In , they enable experimental designs on contemporary panels, while preliminary sketches benefit from the ease of revision before final assembly. However, both methods carry risks of impermanence; cold paints may flake or fade due to environmental exposure, , or mechanical stress, often requiring protective sealants to mitigate deterioration over time. , if imprecise, can lead to uneven surfaces or unintended cracks, emphasizing the need for skilled application to avoid compromising the integrity.

Colors

Transparent and White Glass

Transparent and white serves as the foundational element in stained glass compositions, providing clarity and allowing to illuminate surrounding colored pieces. In historical production, this glass was created by high-purity with (potash) and a small amount of lime in clay pots, without adding metallic oxides to maintain its colorless quality. The resulting glass often exhibited a slight greenish or yellowish tint due to trace iron impurities in the raw materials, along with natural irregularities like bubbles and undulations from mouth-blowing techniques. Modern water-white glass, in contrast, achieves superior clarity through refined manufacturing processes using low-iron silica melts with minimal additives, often produced via rolling methods to form flat sheets suitable for contemporary stained glass work. This ultra-transparent variant transmits up to 92% of visible light, far exceeding the 80-85% of traditional clear glass, making it ideal for applications requiring maximal brightness. The primary effect of transparent and white glass is to maximize transmission, creating luminous backgrounds such as skies, architectural elements, or ethereal halos that enhance the vibrancy of adjacent colored glass without competing for illumination. In medieval European windows, it balanced the intense hues of pot-metal colors, allowing diffuse daylight to flood interiors and emphasize narrative scenes. Variations include frosted or textured surfaces, achieved through acid etching or rolling processes, which scatter light for subtle while preserving overall transparency. These textured whites, such as waterglass with its rippled finish, soften glare and add depth to modern panels.

Green and Blue Glass

Green stained glass is created by adding (CuO) to the molten batch at concentrations typically ranging from 1% to 5%, producing a of tones from vibrant emerald to subdued depending on the base composition and firing conditions. The copper ions in their divalent state (Cu²⁺) absorb light in the and regions of the , transmitting wavelengths to achieve this effect. When iron oxides are present as impurities or intentional additives, they interact with to induce color mutations, shifting hues toward deeper or more yellowish greens through combined absorption bands. Blue stained glass relies on cobalt oxide (CoO) added at low concentrations of 0.1% to 1%, resulting in intense tones that transmit blue light while absorbing in the red and yellow . Cobalt's high extinction coefficient makes it a potent colorant, requiring precise dosing to avoid opacity and ensure translucency for light passage. For lighter blue shades, smalt—a finely ground potassium glass infused with cobalt oxide—is incorporated into the batch or used as a , diluting the intensity to produce sky-like or pale azure effects. In stained glass applications, varieties are commonly employed to represent foliage and landscapes, leveraging their warm transmission to evoke organic vitality under sunlight. , with their cool, expansive absorption properties, depict skies, robes, and celestial motifs, allowing diffused to create ethereal glows. Producing these colors in technique presents challenges in batch consistency, as variations in oxidation states during melting can alter valences, leading to unintended shifts from to or to gray.

Red and Purple Glass

The production of red stained glass has historically been challenging due to the need for precise chemical compositions to achieve vibrant, translucent hues. The most prized red, known as ruby glass, is created by incorporating small quantities of (typically 0.01-0.1% by weight) into the molten mixture, often in the form of derived from dissolving in . This addition forms nanoparticles that scatter light, producing an intense ruby red color through . The process requires careful control during melting and cooling to prevent the gold from precipitating unevenly, and the color often develops fully only after a secondary called "striking," where the is reheated to around 500-600°C to promote nanoparticle formation. Due to the high cost of gold, ruby red remained scarce and expensive in medieval and , limiting its use to high-status commissions until industrial advancements in the made purer gold salts more accessible and reduced production costs. Cheaper alternatives to gold-based reds emerged using copper oxides, which could yield a similar crimson tone when combined with reducing agents like . Copper red glass forms through the precipitation of metallic copper nanoparticles during the cooling phase of production, requiring a controlled, slow cool to avoid oxidation that would dull the color to green or brown. This method, documented in early modern recipes, allowed for more widespread use of in stained but still demanded skilled furnace management to achieve stable, light-transmissive results. The intense transmission of and copper reds through glass symbolizes passion and sacrifice in contexts, evoking the in windows depicting martyrdom or divine love. Purple stained glass, often termed , derives its color from added to the glass batch at concentrations of about 1-3%, which imparts a violet hue by absorbing specific wavelengths of . Unlike colors, manganese purples develop their tone during the initial but can be enhanced through striking—a reheating process similar to that for reds—to intensify the color and ensure even distribution, a technique noted in historical glassmaking treatises from the onward. This color was less scarce than ruby red, as was more readily available, though achieving a pure, non-muddied required balancing against iron impurities that could shift tones toward . In symbolic applications, 's rich, regal glow through glass represented royalty and spiritual authority, frequently bordering figures of Christ or saints to denote divine kingship.

Yellow Glass

Yellow glass in stained glass production is primarily achieved through the application of silver stain, a technique involving silver compounds applied to clear or lightly tinted glass before firing. This method utilizes a mixture of silver (often or ) and sometimes , which, upon firing at temperatures between 500°C and 650°C, forms silver nanoparticles that produce stable yellow hues ranging from pale lemon to deep gold or orange. The tone variation depends on factors such as the silver-to-copper ratio (optimally around 2:1), firing duration, and temperature, with lower temperatures yielding brighter, lighter shades and higher ones producing deeper, more saturated colors. This process, which emerged in the early , marked a significant historical shift by enabling artisans to create consistent yellows without relying solely on pot metal techniques, thus expanding the palette for decorative highlights in medieval windows. The resulting yellow glass is prized for its bright, light-transmissive qualities, allowing it to function effectively as highlights, accents, or simulated golds in larger compositions, where it transmits vividly to enhance overall . Prior to the widespread adoption of silver stain, achieving yellow tones was more limited, but post-1300s innovations made it a staple in European stained glass, particularly in Gothic cathedrals. Alternative methods for producing yellow glass include the incorporation of (0.1% to 2%) into the glass melt, which imparts a fluorescent yellow or greenish-yellow tint that glows under light; this approach was common from the 19th century until the 1940s, when wartime restrictions curtailed availability for civilian use. Another option involves oxide, which can yield pale yellow shades when added during glassmaking, though it is less vibrant and more often associated with white or subtle tints. These alternatives provided variety but were generally supplanted by silver stain for its reliability and control in artistic applications.

Fabrication Process

Design and Planning

The design and planning of stained glass windows commences with the commissioning process, in which a patron—typically a church, , or individual—engages an artist or studio to create a work tailored to specific needs, such as illuminating a or commemorating an event. This stage involves detailed consultations to align the project with the patron's vision, budget, and timeline, often beginning with mood boards or reference images to establish feasibility. Theme selection follows, where the narrative or symbolic content is determined collaboratively, drawing from religious texts, cultural motifs, or personal significance while ensuring compatibility with the site's existing . Preliminary sketches and small-scale maquettes are then produced to explore composition, scale, and balance, allowing iterations based on patron feedback before advancing to the full design. Key influences include the window's architectural integration, such as proportions to fit lancet shapes or windows, and patron stipulations for elements like inscriptions or heraldic symbols. Upon approval of the concept, a full-scale —a precise, life-size on heavy or —is crafted to delineate every lead line, glass shape, and detail, often annotated with color codes (e.g., "b" for ) to guide subsequent fabrication. Light direction is critically evaluated during this phase, as the angle and intensity of natural illumination influence color vibrancy and , ensuring the maximizes translucency when viewed from interior perspectives. Tools such as pounce patterns facilitate accurate tracing: the is pricked with holes along outlines, placed over a surface, and dusted with or using a to transfer the without distortion. This process has evolved from the manual techniques of medieval workshops, where master designers and apprentices collaborated on hand-drawn cartoons using natural light for reference, to contemporary methods incorporating digital tools. Today, software like Adobe Illustrator or specialized CAD programs enables rapid prototyping, simulation of light effects, and precise scaling, while lightboxes provide even illumination for tracing enlarged patterns onto durable media. These advancements streamline revisions and enhance accuracy, particularly for large-scale commissions, without altering the core emphasis on artistic intent and technical precision.

Glass Selection and Preparation

In the fabrication of stained glass, the selection of glass begins with identifying sheets that align with the color palette, texture, and opacity specified in the design . Artisans typically choose from glass, where metallic oxides are mixed into the molten glass batch to create solid, uniformly sheets, or flashed glass, consisting of a thin layer of glass fused onto a thicker clear or lightly tinted base for nuanced effects. This matching process involves holding sample sheets against the cartoon under natural light to assess translucency and tonal variations, ensuring the final window transmits light as intended. Once selected, the glass is cut to precise shapes outlined in the cartoon. Traditional methods employ a hot dividing iron to fracture and break rough forms from larger sheets, followed by grozing irons or to chip away excess edges for refinement; in later periods, diamond-pointed tools or were introduced for cleaner scoring along curved lines. Modern practice often uses pistol-grip glass cutters with wheels to score the surface, combined with running to snap pieces cleanly, allowing for intricate shapes up to several inches in size. Cuts are made slightly larger than the cartoon outlines to accommodate lead cames during assembly. Preparation of the cut pieces may include initial surface treatments to enhance details before full assembly. Vitreous paints, composed of metal oxides like iron or mixed with a flux and binder, are applied by hand to delineate lines, shading, or textures directly on the glass, which is then fired at low temperatures to fuse the paint permanently. For pieces requiring yellow hues or highlights, silver stain—a solution of silver salts—is selectively applied and fired to produce a translucent golden tone without additional layering. Quality checks occur throughout, with each cut piece laid back onto the cartoon to verify fit and alignment, adjusting edges as needed to prevent gaps or overlaps that could compromise structural integrity. This iterative testing ensures uniformity in color distribution and shape accuracy, critical for the window's overall cohesion.

Assembly and Installation

The assembly of stained glass panels begins with fitting the cut and painted glass pieces into H-section lead cames, which are strips of lead with U-shaped channels on opposing sides to securely hold the glass edges. These cames are cut to length using a lead or and inserted around each glass piece, with the panel laid face-down on a to follow the cartoon design precisely. The lead joints are then together using a applied with a hot iron, creating strong, flexible connections that allow the panel to withstand structural stresses. For added stability, the assembled panel is cemented by forcing a mixture—typically and whiting—into the came channels around the , followed by blackening the exterior leads with a or lampblack paste to enhance appearance and prevent oxidation. An alternative assembly method, particularly for smaller panels or curved designs like lampshades, is the copper foil technique. In this process, edges of the glass pieces are wrapped with adhesive copper foil tape, and the foil overlaps are soldered together to join the pieces securely. Large panels require reinforcement to support their weight and prevent sagging; this is achieved by attaching copper wire ties or clips soldered to the lead cames, which connect to saddle bars—flat iron or steel bars spanning the window frame at intervals of about 12 to 18 inches. These saddle bars are fixed into the surrounding or wooden frame with pegs or bolts, distributing the load evenly. Installation entails placing the completed panel into the building's , often a stone or iron frame, where it is bedded in glazing to seal against weather and secured with metal clips or points hammered into the frame to hold it in place. Protective outer glazing, such as clear or acrylic storm panels, may be added to shield against environmental damage while allowing light transmission. In modern practice, alternatives to traditional lead cames include resins or adhesives, particularly in the dalle de verre technique where thick slabs are embedded directly into a or matrix for greater durability and abstract designs.

History

Ancient Origins and Early Developments

The earliest known uses of colored , a precursor to stained glass, date back to the Roman period, where it was employed in techniques for decorative vessels and architectural elements. In the 1st century BCE to 1st century CE, Roman artisans created bowls by fusing bundles of colored canes—thin rods of tinted —into patterns before slumping them into shapes, achieving intricate designs with colors derived from metal oxides. These objects, such as fragmented architectural plaques featuring floral motifs, demonstrate the technical sophistication of early glass coloring but were limited to small-scale items rather than transmissive windows. By the CE, Byzantine craftsmen in regions including modern-day advanced these techniques, incorporating colored glass tesserae into wall mosaics and possibly early window applications. Excavations at sites like Boğazköy reveal Late Roman and Early Byzantine glass fragments from cemeteries, characterized by natron-based compositions typical of the eastern Mediterranean. While large-scale stained glass windows emerged later, evidence from 4th- to 6th-century contexts, such as glass tesserae at in , indicates the use of opaque and colored glass pieces for decorative piercings in , blending filtration with ornamental effects. Early stained glass relied on soda-lime-silica formulations, where silica sand was fluxed with soda ash (from deposits) and lime () to lower melting points, achieving a stable, transparent base around 1000–1100°C. Basic colorants included oxides for greens and blues, iron for yellows and browns, and for purples, added in trace amounts (0.025–1%) to the molten batch for uniform tinting without enameling. These materials, sourced from Mediterranean quarries and Egyptian , enabled durable yet vibrant pieces, though production was artisanal and regionally variable. The application of stained glass remained confined to small objects—beads, vessels, and inlays—until the late 7th century, when it transitioned to architectural windows in monastic settings. In , the earliest surviving examples appear around 680 CE at the of St. Paul's in , where fragments of colored glass from the original church suggest imported techniques from the or Mediterranean, marking the first successful firings for window use in the . This site, dedicated in 685 CE, represents a pivotal early development, with simple colored panes filtering light in a newly established Anglo-Saxon religious context.

Medieval Europe and Southwest Asia

In medieval Europe, stained glass reached its artistic zenith during the Gothic period from the 12th to 15th centuries, particularly in the construction of grand where vast windows served as illuminated narratives for the faithful. The exemplifies this era, with its 13th-century windows comprising over 170 panels that depict biblical stories, saints, and trades, covering approximately 2,600 square meters and remaining largely intact due to their protected installation. These windows transformed church interiors into glowing spaces, using light to symbolize divine presence, and were funded by guilds, , and to educate an illiterate populace through visual storytelling. A key innovation was glass, produced by mixing metallic oxides—such as for or for —directly into the molten batch, creating vibrant, uniform colors throughout the material that allowed for durable, translucent sheets up to several millimeters thick. Complementing this, silver stain emerged around the late as a technique involving the application of silver compounds to one side of clear or lightly tinted , which, when fired, oxidized to produce stable yellow tones ranging from pale lemon to deep , enabling artists to achieve flesh tones and highlights without relying solely on colored . These advancements expanded the palette and detail possible in compositions, moving beyond the bold, blocky forms of Romanesque windows to more nuanced figures and backgrounds. In parallel, stained glass techniques evolved to support expansive narrative designs, with glass paint—made from fluxed with metal oxides—applied in black or brown lines to outline forms, shade areas, and add intricate details like facial expressions and textures before firing to fuse it permanently. This allowed for larger panels, often assembled in lead cames to form multi-light windows up to 10 meters tall, as seen in ' lancet windows, where scenes from Genesis or the life of Christ unfolded across multiple registers, integrating architectural elements like for rhythmic flow. By the 14th and 15th centuries, these methods facilitated even greater complexity, with white glass backgrounds enhancing color contrasts and creating illusory depth in cathedrals like in . In Southwest Asia, during the 7th to 12th centuries under early Islamic rule, techniques for colored glass developed, with early examples of window applications appearing in the 9th century at sites like the Great Mosque of Samarra in Iraq, featuring geometric patterns that aligned with aniconic artistic traditions emphasizing abstraction and infinity. These included silver-stained glass fragments allowing filtered light to project intricate star-and-polygon motifs onto interiors, symbolizing cosmic order without figurative representation. In Iran, the Friday Mosque of Isfahan (11th-12th centuries) incorporated similar geometric window elements, using translucent glass in blues and greens to complement tilework and muqarnas vaults, drawing on advancements in glass production from Syrian and Persian workshops that favored mineral-based coloring for durability in arid climates. Further west in Al-Andalus, the Great Mosque of Cordoba (10th century) featured early colored glass windows with latticed designs, influencing later Islamic and European traditions. These applications prioritized ornamental harmony over narrative, influencing later Islamic decorative arts. The decline of stained glass production in Europe began in the 16th century amid the Protestant Reformation, when iconoclastic fervor led to widespread destruction of religious imagery deemed idolatrous. In the Beeldenstorm of 1566 in the Netherlands and similar upheavals in England and Scotland, mobs and authorities smashed stained glass windows, burying fragments or replacing them with clear panes to purify churches of "popish" adornments, resulting in the loss of thousands of medieval panels. This iconoclasm, rooted in theological rejection of visual aids to worship, severely curtailed patronage and technical continuity, shifting the medium toward secular uses until later revivals.

Renaissance to 19th Century Revivals

During the , stained glass in and began incorporating classical figures and motifs inspired by antiquity, marking a shift from the predominantly religious Gothic styles of the medieval period. In , where Gothic stained glass arrived relatively late, the flourished early in the , with artists drawing on humanist themes and to create windows featuring mythological scenes and balanced compositions influenced by woodcuts and engravings. German stained glass of the same similarly adopted enamel painting techniques, allowing for more detailed portraits of classical deities and historical figures, as seen in roundels and panels that blended traditional pot-metal with painted enamels for vibrant, narrative depth. The Protestant Reformation profoundly disrupted stained glass production and survival across , particularly in Protestant regions where led to widespread destruction of figurative windows deemed idolatrous. In , the in the 1530s resulted in the loss of extensive glazing, such as at St. Mary in York, while royal injunctions under in 1538 and in 1547 targeted religious imagery, destroying panels like those depicting St. Cuthbert in . This era prompted simpler designs in surviving Protestant churches, favoring clear glass or abstract heraldic motifs over elaborate biblical narratives, with enamel-painted white glass emerging as a practical alternative that reduced costs and aligned with reformed aesthetics. By the , interest in stained glass waned amid neoclassical preferences, but revivals gained momentum in the as part of the Gothic Revival movement. In Britain, the Gothic Revival, led by A.W.N. Pugin in the , revitalized medieval techniques using pot-metal colored for richly hued church windows that emphasized moral and religious symbolism, as in Pugin's designs for the Palace of Westminster. France saw a parallel resurgence under Eugène-Emmanuel Viollet-le-Duc, who advocated for historically accurate restorations of Gothic cathedrals like Notre-Dame, integrating authentic stained glass to preserve architectural integrity and narrative traditions. James Powell & Sons, established in when James Powell acquired the Whitefriars Glassworks, became a leading studio in this revival, innovating with traditional methods to produce high-quality Gothic-style windows for churches across Britain and beyond. Colonial stained glass in during the 18th and 19th centuries primarily consisted of imported European windows, reflecting Spanish and influences in religious buildings like Chilean cathedrals, where 19th-century panels from depicted saints and biblical scenes to adorn newly constructed colonial churches. These revivals not only restored technical expertise but also adapted stained glass for secular contexts, such as heraldic designs in public halls.

20th and 21st Century Innovations

In the early 20th century, the movement revitalized stained glass through innovative use of opalescent glass, pioneered by . Tiffany's technique involved layering and streaking colors within the glass itself to create iridescent effects that shifted with light, departing from traditional painted glass in favor of organic, flowing forms inspired by nature. This approach, exemplified in works like the magnolia motifs using drapery glass, emphasized texture and luminosity, influencing secular lamps and windows that blended artistry with domestic design. During the , the school in introduced to stained glass, transforming it into a modern medium for geometric experimentation. The glass painting workshop, established in 1920 under and later led by and , focused on light's interaction with color and form, producing non-figurative panels like Albers's grid-like screens that evoked dynamic spatial effects. These innovations prioritized industrial materials and simplicity, aligning stained glass with Bauhaus principles of functional . In the mid-20th century, stained glass embraced and structural boldness, as seen in Henri Matisse's designs for the Chapel of the in , , completed between 1948 and 1951. Matisse's large-scale windows featured bold, simplified color blocks in blue, yellow, and green, creating an immersive, non-narrative light environment that conveyed spiritual abstraction through pure form and hue. Concurrently, the dalle de verre technique, developed in the 1930s by Jean Gaudin in , gained prominence in the 1950s for embedding thick glass slabs directly into concrete, enabling monumental, textured installations that integrated architecture and sculpture. This method, used in projects like the Fish Church in , , allowed for durable, abstract compositions that diffused light dramatically through irregular edges. The has seen stained glass incorporate digital design tools, LED backlighting for dynamic effects, and sustainable materials, expanding its role in . Artists now use software for precise pattern modeling and fabrication, while recycled glass and low-energy production methods address environmental concerns, as demonstrated by studios like Judson Studios in their adaptive restorations and new commissions. Judith Schaechter exemplifies these advancements, creating intricate, narrative panels with etched and painted elements that explore ecological and psychological themes, such as her 2025 eight-foot dome installation evoking neuroaesthetic joy through layered, luminous narratives. Globally, Japanese artists have fused stained glass with traditional aesthetics, blending motifs and minimalist forms in works like Koki Masato's neo-mosaic panels depicting with refracted light effects. Post-2000 public art commissions have further democratized the medium, with installations like Nekisha Durrett's Art Deco-inspired translucent films on bridges at the Phillips Collection, transforming urban spaces into vibrant, inclusive light experiences. These projects highlight stained glass's evolution into a versatile tool for public engagement and cultural dialogue.

Symbolism and Iconography

Religious and Cultural Meanings

In Christian stained glass, frequently depicts saints and biblical scenes to illustrate key narratives from scripture, serving as visual aids for the faithful. For instance, windows often portray the lives of apostles, martyrs, and Christological events such as the Nativity or , with figures rendered in vibrant colors to emphasize their spiritual significance. Specific color choices carry deep symbolic weight: represents , , and the celestial realm, while symbolizes the , passion, and martyrdom. These elements, as seen in medieval European cathedrals, reinforce theological themes of and divine order. In , stained glass employs non-figurative geometric patterns to evoke spiritual and the unity of (tawḥīd), avoiding representational imagery in adherence to aniconic traditions. Interlocking , polygons, and tessellations in windows symbolize the infinite nature of creation and divine , with filtering through colored glass to manifest metaphysical transparency and cosmic order. Similarly, Jewish stained glass in synagogues favors abstract, non-figurative designs that symbolize the and without violating prohibitions against graven images. Patterns of , , lamps, and eternal flames evoke spiritual illumination and the sacred text's enduring wisdom, as exemplified in mid-20th-century American synagogue windows that use refracted sunlight to suggest the ineffable Divine. Stained glass has also played roles in expressing cultural identities, particularly in colonial , where windows in churches blended European techniques with local motifs to assert national and hybrid identities post-independence. In Chilean colonial and early republican churches, imported European glass incorporated indigenous floral and symbolic elements, reflecting a fusion of Catholic with regional heritage to foster a sense of unified cultural . In Gothic rose windows, esoteric meanings emerge through circular forms symbolizing perfection and eternity, often dedicated to the Virgin Mary as the "rose without thorns," with radiating evoking and Marian . Over time, the symbolism of stained glass has evolved from a primarily didactic tool—intended to teach biblical stories to illiterate congregations in medieval churches—to a meditative form that invites of the divine. Early windows functioned as "Bible of the poor," narrating scripture through vivid scenes, but by the 19th and 20th centuries, revivals emphasized aesthetic and spiritual immersion, using abstract light effects to evoke and personal reflection rather than explicit instruction. This shift highlights stained glass's enduring capacity to transcend narrative, fostering a direct encounter with the sacred through color and .

Artistic and Narrative Roles

Stained glass has long served as a dynamic medium for , employing sequential panels that function similarly to comic strips to unfold across windows. In medieval examples, artists arranged scenes in linear or grid-like formats, allowing viewers to read the progression from left to right or bottom to top, much like modern , to convey extended stories through visual continuity. This technique relied on the interplay of light, which animated the panels by casting shifting colors and shadows, creating a of depth and movement that enhanced the narrative flow without relying on text. Artistically, stained glass embodies principles of balance, color , and scale to achieve compositional unity, often in close collaboration with architects to ensure seamless integration into building structures. Artists balanced dense areas of vibrant hues—achieved by metallic oxides in the glass—with lighter, translucent sections to guide the viewer's eye and prevent visual overload, while scaling figures and motifs proportionally to the window's architectural frame for and aesthetic equilibrium. This between glaziers and builders, evident from Gothic cathedrals onward, treated stained glass not as mere decoration but as an essential element that modulated light and space within the architecture. During the , stained glass expanded into secular narratives, depicting historical events and to commemorate patrons or civic pride in non-religious settings like town halls and private residences. Panels illustrated key moments from antiquity, such as heroic deeds or mythological encounters, using detailed figural compositions to evoke and intellectual discourse among educated viewers. These works shifted focus from didactic sequences to more individualized, emblematic scenes, often incorporating to personalize the narrative for secular audiences. In modern contexts, stained glass has evolved toward abstraction, prioritizing emotional expression through non-literal forms and color dynamics over explicit storytelling. Artists like employed simplified, rhythmic motifs in works such as the Chapel of the Rosary in (1948–1951), where bold geometric shapes and saturated blues and yellows filter light to evoke serenity and spiritual uplift, transcending traditional narratives. Similarly, Judy Chicago's glass series, including "Heads Up" (2018–2019), uses translucent layers and organic forms to channel personal and collective emotions, leveraging the medium's to convey vulnerability and resilience in abstract terms.

Applications

Religious Buildings

Stained glass has been a of religious for centuries, primarily serving to enhance the spiritual atmosphere in places of through colored filtration. In churches, particularly during the Gothic period, it transformed interiors into luminous spaces that symbolized divine presence, with artisans using pot-metal glass and lead cames to create expansive windows that filled naves with ethereal glow. This tradition, rooted in medieval , emphasized the interplay of and color to evoke transcendence, a practice that continues in contemporary designs. In Gothic cathedrals, stained glass reached its zenith, as seen in the in , constructed in the 1240s under King Louis IX, where nearly two-thirds of the structure's walls are devoted to vivid narrative panels depicting biblical scenes in deep blues, reds, and golds. These windows, measuring up to 15 meters in height, were engineered to maximize daylight penetration while maintaining structural integrity through innovative supports. Rose windows, circular designs emblematic of the Gothic style, adorn facades like those at Notre-Dame Cathedral in (completed around 1260), featuring radial spokes that frame intricate floral or geometric motifs, often symbolizing the eye of or the radiating light of . Such installations not only illuminated altars but also guided the congregation's gaze toward sacred narratives during services. Adaptations of stained glass appear in synagogues and mosques, reflecting cultural and religious sensitivities while preserving the medium's luminous qualities. In Jerusalem's , rebuilt in the 19th century, stained glass windows incorporated Hebrew motifs and patterns to evoke Jewish heritage, drawing on European techniques introduced during the Enlightenment era. Islamic architecture, traditionally favoring translucent or colored glass in lanterns, integrated stained glass more prominently in 19th-century Iranian mosques, such as the Nasir al-Mulk Mosque in , where geometric arabesques in azure and emerald hues align with aniconic principles, creating intricate light patterns that enhance prayer halls without representational imagery. Other faiths have embraced stained glass in the , notably in Asian Buddhist temples. In 20th-century and , artists like those at Kyoto's studios crafted windows for temples such as Benchamabophit in (incorporating early 20th-century designs), using opalescent glass to depict lotus motifs and enlightened figures, blending Western methods with Eastern aesthetics to foster meditative environments. Across these diverse worship spaces, stained glass functions to illuminate altars and sanctuaries, casting dynamic colors that cultivate a sacred ambiance and deepen communal rituals.

Secular and Public Structures

Stained glass found its way into domestic settings during the , particularly in affluent homes where it served as decorative elements in doors, transoms, and windows, often featuring floral motifs, geometric patterns, and pastoral scenes to enhance interior aesthetics. This trend was amplified by the Arts and Crafts movement in the late 19th and early 20th centuries, which emphasized handcrafted quality and rejected machine-made alternatives, leading to bespoke panels that integrated seamlessly into residential architecture for both ornamental and light-diffusing purposes. In public and commercial structures, stained glass transitioned from ecclesiastical dominance to civic and functional roles, exemplified by its use in transportation hubs like Glasgow Central Station. During its 1901-1906 expansion, the station incorporated stained glass panels alongside ornate ironwork and canopies, creating a grand, illuminated interior that symbolized industrial progress and public prestige. Similarly, banks adopted stained glass to convey solidity and elegance; the Merchants National Bank in , built in 1912, features elaborate stained-glass windows within its Prairie School design, blending natural light with architectural ornamentation to foster a sense of trust and refinement. The Cleveland Trust Company's rotunda, completed in 1907, includes a massive 61-foot-diameter stained-glass skylight that dominates the space, illuminating marble interiors and underscoring the institution's opulence. Secular memorials also embraced stained glass for commemorative purposes, particularly in war-related tributes outside religious contexts. Harvard University's Memorial Hall, constructed in the late 19th century, contains extensive secular stained-glass windows depicting Civil War scenes and historical figures, marking it as one of the world's largest collections of non-religious narrative glass and honoring alumni sacrifices through vivid, light-infused storytelling. These windows prioritize civic remembrance over spiritual symbolism, using color and form to evoke national history. In mausolea, 19th-century stained glass provided ethereal illumination within private memorial spaces, drawing on opalescent techniques for dramatic effect. Woodlawn Cemetery in New York features over 1,100 such windows in its mausoleums, many from the , where artists like employed layered glass and silver staining to create jewel-like panels that transformed dim interiors into luminous sanctuaries, reflecting the era's wealth and artistic innovation. Contemporary trends in secular and public structures highlight stained glass's versatility in commercial environments, such as offices where it functions as privacy screens and branding elements. In modern American architecture since the , stained glass has appeared in non-religious settings like restaurants and corporate spaces, offering diffused light and custom designs that incorporate logos or abstract patterns to enhance brand identity while maintaining visual separation. Artists like have furthered this evolution, creating large-scale installations for secular buildings that blend traditional craft with bold, contemporary aesthetics to serve functional roles in public lobbies and atriums.

Modern and Sculptural Uses

In the realm of modern stained glass, sculptural applications extend beyond traditional windows to free-standing pieces that emphasize form and light interaction as artistic objects. Louis Comfort Tiffany's leaded-glass lamps, produced from the late 19th to early , exemplify this shift, transforming stained glass into functional yet sculptural forms like the iconic water-lily table lamp, where hand-cut glass panels in vibrant hues are assembled with lead came to create luminous, three-dimensional silhouettes that capture and refract light dynamically. These lamps, often featuring naturalistic motifs such as flowers and insects, were designed for domestic settings, highlighting stained glass's potential as portable art rather than fixed architecture. Public installations further demonstrate stained glass's versatility in contemporary contexts, integrating it into large-scale, site-specific works that engage viewers through color and symbolism. Marc Chagall's "Peace Window" at the Headquarters in New York, installed in , is a monumental example: this 15-foot-wide by 12-foot-high stained glass panel, composed of numerous hand-painted and fired glass pieces, depicts intertwined figures and symbols of harmony, illuminated from behind to project a radiant memorial to UN Secretary-General . Such installations treat stained glass as an immersive medium, where light animation enhances narrative depth without relying on building integration. Contemporary artists continue to push stained glass into sculptural and experimental territories, often blending it with other materials for innovative expressions. British artist , a leading figure since the 1970s, creates freestanding stained-glass screens and leadwork sculptures that explore and symbolism, as seen in his multi-panel compositions that function as autonomous artworks, combining mouth-blown glass with metal framing to achieve bold, modernist geometries. Clarke's works, such as those exhibited at the , incorporate illuminated elements to evoke through shifting light patterns, bridging traditional craft with contemporary . Post-2000 innovations include hybrid techniques, such as fusing stained glass with acrylic for durable, lightweight environmental pieces; for instance, Scottish artist David Mola employs eco-friendly and recycled glass in site-responsive installations that address , like his low-energy fused panels installed in natural settings to highlight ecological themes. Additionally, combinations with metal—such as copper or steel armatures—enable outdoor sculptural forms, as in garden triptychs where stained glass inserts create weather-resistant, light-diffusing structures that evolve with environmental conditions. These developments underscore stained glass's adaptation to sculptural freedom, prioritizing mobility, materiality, and interaction with ambient light.

Conservation and Restoration

Preservation Methods

Preservation of historical stained glass commences with comprehensive condition assessments to evaluate the extent of deterioration, particularly focusing on lead and decay. These surveys typically involve detailed visual inspections, photographic , drawings, and expert by conservation consultants to identify structural weaknesses, such as or sagging caused by corroded lead cames, which generally endure 75 to 200 years before significant degradation. decay, often manifesting as surface leaching, crizzling, or pitting due to , , and temperature fluctuations, is assessed through non-destructive testing to prioritize interventions that halt further environmental damage. Such assessments form the basis for treatment plans, ensuring that preservation efforts are targeted and reversible in line with established ethical standards. Cleaning methods emphasize gentle, non-invasive techniques to remove accumulated dirt, soot, and pollutants without compromising the fragile or painted surfaces. Conservators employ applied via soft or lint-free cloths for initial loose dirt removal, progressing to mild, neutral-pH solvents if needed, while strictly avoiding acidic, ammoniated, caustic, or abrasive cleaners that could etch the , , or dissolve vitreous paints. Localized cleaning is preferred to minimize handling, with immersion or soaking reserved for severely soiled panels only after justification in the assessment report; post-cleaning, surfaces are rinsed and dried carefully to prevent residue buildup. Protective glazing complements cleaning by installing ventilated outer or inner layers—often low-iron spaced ⅝ to 1 inch (16-25 mm) from the original—to shield against rain, wind-driven pollutants, and while promoting airflow to mitigate and internal . Repair techniques prioritize structural stabilization and aesthetic restoration through re-leading and infilling, always favoring work to retain original fabric where possible. Re-leading involves carefully removing deteriorated lead cames and replacing them with historically accurate profiles using pure lead or lead alloys, soldered at joints, but only when threatens collapse, as excessive handling accelerates decay. For missing or broken pieces, conservators voids with compatible glass selected for matching color, transparency, and to the originals, often sourced from or custom-molded stock; small losses may use tinted for stability, applied reversibly to avoid altering the window's light transmission. These repairs adhere to international standards, such as the Corpus Vitrearum guidelines developed in collaboration with ICOMOS since the , which mandate minimal intervention, full documentation, and treatments that are reversible and do not mislead future viewers about the original appearance.

Challenges and Modern Practices

Stained glass preservation faces significant challenges from environmental factors that accelerate deterioration. , including airborne particulates, , and acidic rain, deposits grime on surfaces, corroding lead cames and fading painted details while reducing light transmission through oxidation. from nearby , , or building movements causes existing cracks in glass panels to propagate, as edges grind against each other, potentially leading to complete breakage. Additionally, mismatches in between , lead, and surrounding frames during temperature fluctuations induce stress, resulting in metal , cam bowing, and further cracking, particularly in climates with wide seasonal variations. Contemporary conservation practices incorporate advanced technologies to mitigate these threats without compromising the artwork's integrity. High-resolution 3D structured scanning enables precise documentation and monitoring of stained windows, creating digital replicas for , condition assessment, and non-invasive restoration planning, as demonstrated in workflows for historical sites. UV filters integrated into protective glazing systems block harmful , preventing further fading of pigments and while allowing visible passage. Climate control measures, such as ventilated secondary glazing with maintained air gaps of ⅝ to 1 inch (16-25 mm), regulate temperature and to minimize , , and ingress in both architectural and settings. Ethical considerations in stained glass restoration often revolve around balancing authenticity with necessary intervention, raising debates on the extent of replacement versus repair to preserve historical value. Conservators must weigh the of age against modern reinforcements, ensuring interventions are reversible and minimal to avoid altering the original aesthetic or narrative intent. A prominent is the 1984 York Minster fire, where intense heat exceeding 450°C caused over 40,000 cracks in the South Transept's , prompting a four-year restoration involving meticulous piece-by-piece re-leading and glass repair at a cost of over $4 million, which highlighted tensions between rapid intervention for structural stability and long-term authenticity assessments. Ongoing reviews, such as the 2025 project analyzing the window's post-restoration condition, underscore the need for ethical frameworks that prioritize evidence-based decisions. Looking to the future, stained glass preservation emphasizes sustainable materials and innovative tools to enhance durability and reduce environmental impact. The adoption of lead-free solders and eco-friendly glass compositions addresses toxicity concerns and regulatory pressures, enabling more sustainable repairs. Open-source of polycarbonate-based alternatives offers energy-efficient replicas for high-risk installations, minimizing resource use in restorations. Emerging in analyze historical patterns and material properties to generate precise restoration templates, potentially streamlining complex reconstructions while ensuring fidelity to originals.

References

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