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Bone china
Bone china is a type of vitreous, translucent pottery, the raw materials for which include bone ash, feldspathic material and kaolin. It has been defined as "ware with a translucent body" containing a minimum of 30% of phosphate derived from calcined animal bone or calcium phosphate. Bone china is amongst the strongest of whiteware ceramics, and is known for its high levels of whiteness and translucency. Its high strength allows it to be produced in thinner cross-sections than other types of whiteware. Like stoneware, it is vitrified, but is translucent due to differing mineral properties.
In the mid-18th century, English potters had not succeeded in making hard-paste porcelain (as made in East Asia and Meissen porcelain), but found bone ash a useful addition to their soft-paste porcelain mixtures. This became standard at the Bow porcelain factory in London (operating from around 1747), and spread to some other English factories. The modern product was developed by the Staffordshire potter Josiah Spode in the early 1790s. Spode included kaolin, so his formula, sometimes called "Staffordshire bone-porcelain", was effectively hard-paste, but stronger, and versions were adopted by all the major English factories by around 1815.
From its initial development and up to the latter part of the 20th century, bone china was almost exclusively an English product, with production very largely localised in Stoke-on-Trent. Most major English firms made or still make it, including Spode, Royal Worcester, Royal Crown Derby, Royal Doulton, Wedgwood, and Mintons. In the 20th century it began to be made in other places, including Russia, China, and Japan. China is now the world's largest manufacturer.
In the UK, references to "china" or "porcelain" can refer to bone china, and "English porcelain" has been used as a term for it both in the UK and around the world.
The first development of what would become known as bone china was made in 1748 by Thomas Frye at his Bow porcelain factory near Bow, East London. His factory was located very close to the cattle markets and slaughterhouses of London and Essex, and hence had easy access to animal bones. Frye used up to 45% bone ash in his formula to create what he called "fine porcelain".
Josiah Spode in Stoke-on-Trent further developed the concept between 1789 and 1793, and introduced his "Stoke China" in 1796. He died suddenly the following year, and his son Josiah Spode II quickly rechristened the ware "bone china". Among his developments was to abandon Frye's procedure of calcining the bone together with some of the other raw body materials, instead calcining just the bone. Bone china quickly proved to be highly popular, leading to its production by other English pottery manufacturers. Both Spode's formula and his business were successful: his proportions of 6 parts bone ash, 4 parts china stone and 3.5 parts kaolin remains the basis of all bone china. It was only in 2009 that his company, Spode, went into receivership before eventually being purchased by Portmeirion Pottery.
The traditional formula for bone china is about 25% kaolin, 25% China stone and 50% bone ash.
The bone ash that is used in bone china has traditionally been made from cattle bones, which have a lower iron content. These bones are crushed before being degelatinised and then calcined at around 1,000 °C to produce bone ash. The ash is milled to a fine particle size. The kaolin component of the body is needed to give the unfired body a plasticity which allows pieces to be shaped. This mixture is then fired at around 1200 °C. The raw materials for bone china are expensive, and the production is labour-intensive, which is why bone china maintains a luxury status and high prices.
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Bone china
Bone china is a type of vitreous, translucent pottery, the raw materials for which include bone ash, feldspathic material and kaolin. It has been defined as "ware with a translucent body" containing a minimum of 30% of phosphate derived from calcined animal bone or calcium phosphate. Bone china is amongst the strongest of whiteware ceramics, and is known for its high levels of whiteness and translucency. Its high strength allows it to be produced in thinner cross-sections than other types of whiteware. Like stoneware, it is vitrified, but is translucent due to differing mineral properties.
In the mid-18th century, English potters had not succeeded in making hard-paste porcelain (as made in East Asia and Meissen porcelain), but found bone ash a useful addition to their soft-paste porcelain mixtures. This became standard at the Bow porcelain factory in London (operating from around 1747), and spread to some other English factories. The modern product was developed by the Staffordshire potter Josiah Spode in the early 1790s. Spode included kaolin, so his formula, sometimes called "Staffordshire bone-porcelain", was effectively hard-paste, but stronger, and versions were adopted by all the major English factories by around 1815.
From its initial development and up to the latter part of the 20th century, bone china was almost exclusively an English product, with production very largely localised in Stoke-on-Trent. Most major English firms made or still make it, including Spode, Royal Worcester, Royal Crown Derby, Royal Doulton, Wedgwood, and Mintons. In the 20th century it began to be made in other places, including Russia, China, and Japan. China is now the world's largest manufacturer.
In the UK, references to "china" or "porcelain" can refer to bone china, and "English porcelain" has been used as a term for it both in the UK and around the world.
The first development of what would become known as bone china was made in 1748 by Thomas Frye at his Bow porcelain factory near Bow, East London. His factory was located very close to the cattle markets and slaughterhouses of London and Essex, and hence had easy access to animal bones. Frye used up to 45% bone ash in his formula to create what he called "fine porcelain".
Josiah Spode in Stoke-on-Trent further developed the concept between 1789 and 1793, and introduced his "Stoke China" in 1796. He died suddenly the following year, and his son Josiah Spode II quickly rechristened the ware "bone china". Among his developments was to abandon Frye's procedure of calcining the bone together with some of the other raw body materials, instead calcining just the bone. Bone china quickly proved to be highly popular, leading to its production by other English pottery manufacturers. Both Spode's formula and his business were successful: his proportions of 6 parts bone ash, 4 parts china stone and 3.5 parts kaolin remains the basis of all bone china. It was only in 2009 that his company, Spode, went into receivership before eventually being purchased by Portmeirion Pottery.
The traditional formula for bone china is about 25% kaolin, 25% China stone and 50% bone ash.
The bone ash that is used in bone china has traditionally been made from cattle bones, which have a lower iron content. These bones are crushed before being degelatinised and then calcined at around 1,000 °C to produce bone ash. The ash is milled to a fine particle size. The kaolin component of the body is needed to give the unfired body a plasticity which allows pieces to be shaped. This mixture is then fired at around 1200 °C. The raw materials for bone china are expensive, and the production is labour-intensive, which is why bone china maintains a luxury status and high prices.