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Sizing
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Sizing
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Sizing or size is a substance that is applied to, or incorporated into, other materials—especially papers and textiles—to act as a protective filler or glaze. Sizing is used in papermaking and textile manufacturing to change the absorption and wear characteristics of those materials.

Sizing is used for oil-based surface preparation for gilding (sometimes called mordant in this context). It is used by painters and artists to prepare paper and textile surfaces for some art techniques. Sizing is used in photography[1] to increase the sharpness of a print, to change the glossiness of a print, or for other purposes depending on the type of paper and printing technique.

Fibers used in composite materials are treated with various sizing agents to promote adhesion with the matrix material.

Sizing is used during paper manufacture to reduce the paper's tendency when dry to absorb liquid, with the goal of allowing inks and paints to remain on the surface of the paper and to dry there, rather than be absorbed into the paper. This provides a more consistent, economical, and precise printing, painting, and writing surface. This is achieved by curbing the paper fibers' tendency to absorb liquids by capillary action. In addition, sizing affects abrasiveness, creasability, finish, printability, smoothness, and surface bond strength and decreases surface porosity and fuzzing.

There are three categories of papers with respect to sizing: unsized (water-leaf), weak sized (slack sized), and strong sized (hard sized). Waterleaf has low water resistance and includes absorbent papers for blotting. Slack sized paper is somewhat absorbent and includes newsprint, while hard sized papers have the highest water resistance, such as coated fine papers and liquid packaging board.

There are two types of sizing: internal sizing, sometimes also called engine sizing, and surface sizing (tub sizing). Internal sizing is applied to almost all papers and especially to all those that are machine made, while surface sizing is added for the highest grade bond, ledger, and writing papers.

Surface sizing

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Surface sizing solutions consist of mainly modified starches and sometimes other hydrocolloids, such as gelatine, or surface sizing agents such as acrylic co-polymers. Surface sizing agents are amphiphilic molecules, having both hydrophilic (water-loving) and hydrophobic (water-repelling) ends. The sizing agent adheres to substrate fibers and forms a film, with the hydrophilic tail facing the fiber and the hydrophobic tail facing outwards, resulting in a smooth finish that tends to be water-repellent. Sizing improves the surface strength, printability, and water resistance of the paper or material to which it is applied. In the sizing solution, optical brightening agents (OBA) may also be added to improve the opacity and whiteness of the paper or material surface.

Internal sizing

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See also: Wet strength

Usual internal sizing chemicals used in papermaking at the wet end are alkyl ketene dimer (AKD) and alkyl succinic anhydride (ASA) in neutral pH conditions, and the more ancient rosin system which requires acidic conditions and is still used in some mills.

Preservation

[edit]

While sizing is intended to make paper more suitable for printing, acidic sizing using rosin also makes printing paper less durable and poses a problem for preservation of printed documents.

Sizing with starch was introduced quite early in the history of papermaking.[2] Dard Hunter in Papermaking through Eighteen Centuries[3] corroborates this by writing, "The Chinese used starch as a size for paper as early as A.D. 768 and its use continued until the fourteenth century when animal glue was substituted."[3] In the early modern paper mills in Europe, which produced paper for printing and other uses, the sizing agent of choice was gelatin, as Susan Swartzburg writes in Preserving Library Materials': "Various substances have been used for sizing through the ages, from gypsum to animal gelatin."[4] Hunter describes the process of sizing in these paper mills in the following:

The drying completed, the old papermakers dipped their paper into an animal size that had been made from the parings of hides, which they procured from the parchment-makers. It was necessary to size that paper so that it would be impervious to ink, but sizing was more needed in writing than in printing papers. Many books of the fifteenth century were printed upon paper that had not been sized, this extra treatment not being essential for a type impression. The sizing was accomplished by a worker holding a number of sheets by the aid of two wooden sticks, and dipping the paper into the warm gelatinous liquid. The sheets were then pressed to extract the superfluous gelatine. This crude method of sizing the paper was extremely wasteful as many sheets were torn and bruised beyond use. The sizing room of the early paper mills, was, for this reason, known as the 'slaughter-house'.[3]

With the advent of the mass production of paper, the type of size used for paper production also changed. As Swartzburg writes, "By 1850 rosin size had come into use. Unfortunately, it produces a chemical action that hastens the decomposition of even the finest papers."[5] In the field of library preservation it is known "that acid hydrolysis of cellulose and related carbo-hydrates [sic] is one of the key factors responsible for the degradation of paper during ageing."[6] Some professional work has focused on the specific processes involved in the degradation of rosin-sized paper,[7] in addition to work on developing permanent paper and sizing agents that will not eventually destroy the paper.[8] An issue on the periphery to the preservation of paper and sizing, is washing, which is described by V. Daniels and J. Kosek as, "The removal of discolouration ... in water is principally effected by the dissolution of water-soluble material; this is usually done by immersing paper in water."[9] In such a process, surface level items applied to the paper, such as size in early paper making processes as seen above, have the possibility of being removed from the paper, which might have some item specific interest in a special collections library. With later processes in paper making being more akin to "engine sizing," as H. Hardman and E. J. Cole describe it, "Engine sizing, which is part of the manufacturing process, has the ingredients added to the furnish or stock prior to sheet formation,"[10] the concern for the removal of size is less, and as such, most literature focuses on the more pressing issue of preserving acidic papers and similar issues.

Gilding

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Sizing is a term used for any substance which is applied to a surface before gilding in order to ensure adhesion of the thin gold layer to the substrate. Egg whites have often been used as sizing; the Ancient Egyptians sometimes used blood.[11] Other commonly used traditional materials for gold leaf sizing are rabbit-skin glue diluted and heated in water (water gilding), and boiled linseed oil (oil gilding); modern materials include polyvinyl acetate.

Textile warp sizing

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Sizing the warp

Textile warp sizing, also known as tape sizing, of warp yarn is essential to reduce breakage of the yarn and thus production stops on the weaving machine. On the weaving machine, the warp yarns are subjected to several types of actions i.e. cyclic strain, flexing, abrasion at various loom parts, and inter yarn friction.

With sizing, the strength—abrasion resistance—of the yarn will improve and the hairiness of yarn will decrease. The degree of improvement of strength depends on adhesion force between fiber and size, size penetration, as well as encapsulation of yarn. Different types of water soluble polymers called textile sizing agents/chemicals such as modified starch, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and acrylates are used to protect the yarn. Also wax is added to reduce the abrasiveness of the warp yarns. The type of yarn material (e.g. cotton, polyester, linen), the thickness of the yarn, and the type of weaving machinery will determine the sizing recipe.

Often, the sizing liquor contain mutton tallow. Mutton tallow is an animal fat, used to improve abrasion resistance of yarns during weaving.

The sizing liquor is applied on warp yarn with a warp sizing machine. After the weaving process, the fabric is desized (washed).

Sizing may be done by hand, or in a sizing machine.[12]

Canvas sizing for oil painting

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Preparation of canvas for the oil painting always includes sizing: the canvas will "rot" if directly exposed to the paint. Aqueous glue, frequently the hide glue was used for sizing the canvas for centuries,[13] Size in art is not a replacement for ground: it is not intended to form a level surface for painting, it is used to simply fill pores and isolate the canvas from the actual ground.[14]

See also

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References

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Sources

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Sizing

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from Grokipedia
Sizing is a process used in , , and other fields to apply materials that modify the absorption, strength, and wear characteristics of substrates such as , , or canvases. In textiles, it primarily involves applying a protective coating, known as , to warp to enhance smoothness, strength, and weaveability during . This coating binds yarn fibers, reducing , hairiness, and breakage while increasing elasticity and tensile strength, especially for or filament . Sizing is mainly applied to warp yarns to withstand weaving stresses from heddles and reeds, minimizing defects and ensuring fabric quality. Key objectives include improving abrasion resistance, eliminating static in synthetics, and ensuring uniform weight and stretch for stable beams. Sizing agents are natural (e.g., starches, , proteins like , comprising about 75% of use) or synthetic (e.g., , polyacrylates). They are applied as viscous solutions via immersion, drying on machines like slashers. Modern techniques include hot-melt, , electrostatic, and sizing for efficiency and reduced water use. Environmentally, generates high BOD and uses up to 30% of process water, driving biodegradable agents (e.g., , avocado seed ) and no-desizing methods. Sizing remains vital for high-speed production across materials.

Introduction and History

Definition and General Applications

Sizing refers to the application of substances such as starches, gelatins, or synthetic polymers to materials like , textiles, and canvases, either incorporated during formation or applied to the surface, to fill pores, reduce absorption, enhance , and improve properties like smoothness and printability. These agents act as protective fillers or glazes that modify surface wettability, increase tensile strength, prevent fraying, and promote better in subsequent processes such as or . In , sizing imparts water resistance to reduce bleeding and enhance print quality, while in textiles, it coats warp yarns to protect them from abrasion during and improve overall fabric strength. For artistic applications, sizing seals surfaces to prevent from soaking into the fibers, thereby preserving the support's integrity over time. In , specialized sizing adhesives facilitate the of to substrates by creating a tacky bonding layer. Emerging uses include supporting photographic emulsions on by controlling absorbency for even , and reinforcing fibers in composite materials to improve interfacial and mechanical performance. A key distinction in sizing methods involves wet-end (internal) application, where agents are added to the fiber slurry before sheet formation to hydrophobize the material internally, versus dry-end (surface) application, which coats the formed sheet to create a protective outer film. This differentiation allows tailored control over material properties depending on the end use.

Historical Development

The earliest known application of sizing techniques dates back to ancient , where was employed to strengthen around A.D. 768, providing a smoother surface suitable for writing and enhancing . This marked an initial effort to impart water resistance and improve quality in early processes. In medieval , sizing evolved with the adoption of and animal glues, primarily for treating and nascent production between the 12th and 15th centuries. sizing, documented as early as 1276 at the Fabriano mill in , became a standard practice by the , offering better and against compared to earlier methods. These animal-based agents were applied externally to surfaces, reflecting the era's reliance on natural colloids for material enhancement in manuscripts and early printed works. The industrial era brought significant mechanization and chemical advancements to sizing. In , Moritz Friedrich Illig introduced rosin-alum sizing in 1807, enabling internal application during acidic production and revolutionizing scalable water repellency. Concurrently, the Fourdrinier machine, patented in 1807, facilitated continuous sheet formation, which necessitated efficient internal sizing for . In textiles, William Radcliffe and Thomas Johnson mechanized warp sizing with their beam warper and dressing machine inventions in 1803–1804, automating the application of starch-based sizes to improve efficiency. The witnessed a shift from natural agents like and to synthetic alternatives for superior performance. (AKD) emerged in the late 1950s as a reactive internal sizing agent, forming covalent bonds with under neutral or alkaline conditions to enhance hydrophobicity without acidity. By the , alkenyl succinic anhydride (ASA) gained prominence during the widespread adoption of alkaline , offering rapid reactivity and efficiency in high-speed mills, though requiring careful emulsification to prevent . These developments underscored a broader transition toward more stable, process-compatible sizing for industrial demands.

Papermaking Sizing

Internal Sizing

Internal sizing in involves the of hydrophobic agents to the pulp at the wet end of the process, prior to sheet formation on the , where these agents react with cellulosic s to create barriers that resist water penetration. This wet-end incorporation ensures uniform distribution throughout the , enhancing bulk hydrophobicity and influencing such as absorbency and strength. Typical levels range from 0.05% to 0.25% based on dry weight, with retention promoted by cationic starches or other aids to anchor the agents on fiber surfaces. The primary internal sizing agents include , (AKD), and alkenyl succinic anhydride (ASA), each operating through distinct chemical mechanisms tailored to paper pH conditions. sizing, the earliest method, was developed in 1807 by Moritz Friedrich Illig and requires an acidic environment ( 4.5–5.5) along with as a to form insoluble calcium or aluminum resinate precipitates that deposit on fibers via ionic interactions. In contrast, AKD and ASA enable neutral to alkaline sizing ( 7–8.5), with AKD forming covalent β-keto bonds with hydroxyl groups through a reaction, often requiring curing time or heat for full efficacy. ASA, structurally similar but more reactive, undergoes ring-opening to form linkages with , though it hydrolyzes rapidly in water if not quickly retained, necessitating on-site preparation. The basic reaction for AKD sizing can be represented as follows, where the ketene moiety reacts with a cellulose hydroxyl group: \ce(R−CH2−CH2)2C=C=O+Cell−OH−>(R−CH2−CH2)2CH−C(=O)−O−Cell+H2O\ce{(R-CH2-CH2)2C=C=O + Cell-OH -> (R-CH2-CH2)2CH-C(=O)-O-Cell + H2O} This β-keto ester linkage provides permanent hydrophobicity by orienting alkyl chains away from the surface. These agents reduce penetration into the matrix, improving dimensional stability during printing or writing by minimizing swelling and cockling, though excessive sizing can lower and complicate by hindering repulping. In modern practice, AKD and ASA dominate internal sizing for neutral and alkaline , comprising the majority of global applications in the 21st century due to compatibility with fillers and superior efficiency over . persists in some acidic systems but represents a declining share as mills shift to neutral processes.

Surface Sizing

Surface sizing in involves the application of sizing agents to the exterior of the already formed and partially dried sheet, typically at the size press stage, to enhance surface properties such as printability and handling without significantly affecting the bulk characteristics of the . This occurs after the initial web formation and , where the passes through a size press that meters and applies the sizing solution, followed by further to set the film. Common application methods include flooded nip (tub) size presses, metering blade coaters, and calendar-integrated systems, which allow for controlled penetration and uniform coverage. Agents such as modified starches, , and acrylic emulsions are frequently used, with the solution typically applied at solids concentrations of 5-12% to achieve dry pickup rates of approximately 0.5-2% by weight of the base . Key sizing agents in surface sizing include starch derivatives like cationic and oxidized starches, which promote better penetration and formation due to their altered charge and properties; cationic starches, for instance, improve bonding and retention through electrostatic interactions, while oxidized variants enhance strength via . Synthetic polymers, such as styrene-maleic anhydride (SMA) copolymers or styrene acrylate emulsions (SAE), are employed for achieving high-gloss finishes and superior surface strength, forming a continuous that bonds loose fibers. , often stilbene derivatives, are incorporated to boost whiteness by absorbing UV light and emitting blue fluorescence, with compatibility ensured in alkaline sizing formulations. These agents work mechanistically by creating a hydrophobic surface layer that limits liquid ingress while maintaining flexibility. The primary effects of surface sizing include improved ink holdout, which prevents excessive absorption and ensures sharp print images; reduced picking and linting during by strengthening surface fibers; enhanced for better and reduced roughness; and increased resistance on the exposed surface, achieved through the formation of a barrier that repels without penetrating deeply into the sheet. This treatment is particularly common in coated papers used for magazines and high-quality prints, where it supports offset and inkjet processes by minimizing feathering and improving color density. In recent developments, fluorochemical additives have been integrated into surface sizing formulations to provide grease and oil resistance, especially for applications, where they create low-surface-energy barriers that repel , though usage has evolved toward reduced-fluorine alternatives due to environmental concerns. Techniques for uniform application often involve horizontal sizing presses, which orient the rolls parallel to the paper path for even distribution and minimal sheet at high speeds up to 1,000 m/min, contrasting with vertical presses that may cause more drainage variability. Post-application drying is typically accomplished using heaters for rapid initial evaporation or dryers to cure the film without scorching, ensuring the sizing layer adheres firmly while preserving dimensions. These methods allow precise control over pickup and penetration, optimizing outcomes for specific grades like lightweight coated papers.

Textile Sizing

Warp Sizing Process

The warp sizing process involves applying a protective of solution to warp yarns to enhance their against abrasion and tension during high-speed . This preparatory step occurs after warping, where multiple yarns from creels are fed into a , immersed in a viscous bath typically containing 8-12% solids, then passed through squeeze rolls to control add-on levels (usually 8-15% for yarns), dried using heated cylinders or cans, and finally wound onto a beam for . The process aims to bind fibers, reduce hairiness, and minimize breakage rates, enabling efficient production on modern looms operating at speeds up to 800-1000 picks per minute. Key machinery in the warp sizing includes creels that hold supply beams with up to 1000 or more ends, immersion baths or size boxes where yarns are submerged for 1-2 seconds to ensure penetration, and squeeze rolls made of rubber or synthetic materials that apply pressure (up to 20-30 kN/m) to remove excess size and achieve uniform coating. Following squeezing, the yarns pass over multiple dry cans—typically 5 to 13 heated cylinders at 100-120°C—to evaporate and cure the size , with the entire operation running at speeds of 30-60 m/min in industrial settings. Modern sizing machines incorporate automated controls for tension, , and size to ensure consistent quality across beam lengths of 100-200 meters. Sizing agents are selected based on yarn type, with natural starches such as , , or starch serving as primary binders for and cellulosic fibers due to their film-forming properties and biodegradability. Synthetic agents like (PVA) and polyacrylates are preferred for synthetic fibers such as , offering superior adhesion and allowing lower add-on rates of 5-10%. Additives enhance performance, including waxes or oils (e.g., at 5-7.5% of starch weight) for to reduce , and antistatic agents like to prevent yarn buildup during . The mechanism of warp sizing relies on the formation of a thin, film around individual yarns, which binds protruding fibers, increases tensile strength by 20-50% through improved cohesion, and shields against mechanical stresses in the . For instance, starch-grafted polyacrylate formulations have demonstrated breaking strength improvements from 39.86 N·mm⁻² to 62.62 N·mm⁻² in yarns, while reducing hairiness and warp breaks. This protective layer is essential for high-speed , where unsized yarns can experience breakage rates exceeding 1-2% per 1000 meters, but sized yarns maintain efficiency above 90%. follows to remove the size for fabric finishing. Warp sizing was mechanized in the early , with William Radcliffe and Thomas Johnson patenting the first sizing machine in 1803-1804 to handle larger warps efficiently amid the Industrial Revolution's demand for powered looms. In modern practice, beam sizing for synthetic fibers uses reduced size add-ons (5-10%) compared to traditional methods (10-15% for ), reflecting advancements in agent formulation and machinery precision. Environmentally, high- sizing generates with elevated (BOD) from natural agents, prompting shifts toward biodegradable synthetics or grafted starches to lower loads by 20-30%.

Desizing

Desizing is the process of removing sizing agents applied to warp yarns during , typically performed in scouring baths prior to wet steps such as or . This removal breaks down the protective size films—often starch-based or synthetic—through enzymatic, oxidative, or acidic , restoring the fabric's natural properties and ensuring uniform treatment in subsequent stages. The process targets warp sizing agents to eliminate residues that could otherwise hinder absorbency or cause processing defects. Key desizing methods include enzymatic , which employs amylases to degrade sizes on fabrics, operating optimally at temperatures of 30–60°C or 95–100°C and pH 5.5–6.5 for low- or high-temperature variants, respectively. Oxidative desizing utilizes , often combined with , to oxidize and solubilize synthetic or -based sizes, particularly effective for blended fabrics but requiring careful control to avoid fiber damage. Acidic , such as steeping in dilute sulfuric or (e.g., 0.1N HCl), hydrolyzes or (PVA) sizes into soluble forms, typically at for 6–8 hours followed by rinsing, though it risks degradation if not managed properly. The primary effects of desizing include restoration of fabric absorbency and prevention of dyeing defects, such as uneven color uptake due to residual size barriers, enabling better penetration of dyes and chemicals. Efficiency is quantified by size removal percentages, with >95% considered ideal for optimal performance, assessed through metrics like the iodine test (Tegewa scale), where a rating of 9 indicates near-complete starch removal (residual <0.08%), or weight loss analysis comparing pre- and post-desizing fabric masses. Modern eco-friendly approaches leverage biodegradable enzymes, such as indigenously produced amylases from , to minimize chemical effluent, reducing biochemical oxygen demand (BOD) and total dissolved solids (TDS) in wastewater compared to traditional acid or oxidative methods. Challenges arise with blended yarns, like polyester-cotton, necessitating multi-step processes to address synthetic components and auxiliaries that complicate uniform size degradation.

Artistic and Decorative Sizing

Canvas Preparation for Painting

Canvas preparation for painting involves applying a sizing layer to raw to seal its fibers and create a barrier against oil-based paints, a practice essential for preventing long-term deterioration. Traditionally, the process begins with stretching the —typically —over wooden or strainers to ensure tautness. An aqueous glue solution is then brushed or sponged onto of the in one to two thin coats, allowing each layer to dry thoroughly before the next application; this step is distinct from subsequent priming with , which provides the surface. Drying occurs at , often taking 24 hours per coat, to avoid uneven contraction. The primary sizing agents are animal-based glues, such as rabbit-skin glue or hide glue, prepared as a 5-10% solution by soaking granules in cold water (typically 1 part glue to 10-12 parts water) and heating gently to around 50°C in a double boiler until fully dissolved into a viscous liquid. These glues, derived from collagen in animal hides, have been used since the late 15th century in Italian Renaissance oil painting techniques, where they were applied to canvas supports emerging as alternatives to wood panels for their portability and lower cost. The mechanism works by filling the weave pores of the canvas, blocking the migration of oils from paints and grounds, which could otherwise cause rot, brittleness, and cracking in the fibers; additionally, sizing enhances paint adhesion while preserving the canvas's natural texture. Without proper sizing, direct application of oil paint can lead to eventual degradation of the canvas fibers due to oil absorption and oxidation. Modern alternatives to animal glues include acrylic mediums, such as gloss or emulsions diluted to a thin consistency, which offer greater flexibility and resistance to humidity fluctuations compared to traditional options. These synthetic agents are applied similarly via brushing for even coverage, often in a single coat, and dry faster without the need for heating. Acrylic sizing maintains the sealing function to prevent oil penetration while reducing the risk of stiffening or cracking in varying climates, making it suitable for contemporary artists concerned with in humid environments. Applying multiple thin layers of either traditional or modern ensures uniform protection without altering the canvas's pliability, a key factor in the overall durability of oil paintings.

Gilding Techniques

Gilding techniques employ sizing as an essential adhesive layer to secure or onto surfaces in , creating opulent finishes on items such as books, picture frames, and . The process begins with surface preparation, where a sizing agent is applied to form a tacky base, followed by the careful laying of thin leaf sheets and final burnishing to compress the metal and reveal its luster. This method ensures durable while allowing the leaf to conform to intricate details, producing a reflective, high-polish effect prized in historical and contemporary craftsmanship. Traditional sizing agents include mixed with Armenian bole, a fine clay that provides both color and a smooth, absorbent ground for the leaf. Armenian bole, rich in , enhances the gold's warmth and aids in achieving a burnished shine when combined with the glue's binding properties. glair, derived from beaten egg whites allowed to settle, serves as a water-based size in raised , particularly for illuminated manuscripts and edges, offering a clear, flexible that dries to a subtle tack. In contrast, modern synthetic water-based adhesives, such as acrylic emulsions, provide options suitable for conservation and restoration, offering neutral stability to prevent yellowing and reversible for delicate applications. The mechanism of sizing in relies on the creating a slightly tacky surface that captures the delicate without tearing it, while the underlying bole or glue layer absorbs excess to prevent bubbling. Once applied, burnishing with stones or tools compresses the into the size, polishing it to a mirror-like finish and embedding it firmly against environmental wear. This interplay of and compression distinguishes from mere application, ensuring longevity and visual depth. Historically, with sizing traces back to around 2300 BCE, where was applied to for illuminated scenes in funerary texts, using natural adhesives such as organic binders combined with plaster or bole to bind the metal. By the , water techniques evolved for surfaces, involving or glue sizes to reverse-gild designs visible through transparent panels, as seen in Victorian verre églomisé mirrors and . Contemporary practitioners often incorporate distress techniques, such as selective rubbing with fine abrasives or applying glazes post-burnishing, to simulate antique effects on frames and furniture, evoking aged without compromising structural integrity. Essential tools include the gilder's tip, a wide, soft squirrel-hair designed for delicately picking up and positioning without direct contact, minimizing fingerprints and waste. Application steps involve brushing the evenly, allowing it to dry to tackiness—typically 1 to 24 hours depending on and , with warmer conditions accelerating the process—before laying the in overlapping sections. Post-application, light mopping removes excess, followed by burnishing in circular motions to reveal the gleam, ensuring the sized surface withstands handling.

Preservation and Advancements

Preservation Concerns

Historical and traditional sizing agents, particularly acidic used in , contribute significantly to the long-term degradation of paper-based materials through acid-catalyzed , leading to embrittlement and reduced mechanical strength. This process is exacerbated in acidic conditions (pH around 4.7-5.7), contributing to phenomena such as , where localized stains form due to increased acidity and microbial activity. In textiles, starch-based sizes serve as sources that attract mold growth under humid conditions, promoting fungal colonization and weakening when relative humidity exceeds 70%. The primary degradation mechanisms involve acid migration from alum-rosin complexes, which generates ions that catalyze the scission of chains, progressively shortening lengths and causing . In gilded surfaces, oxidation of non-pure metal leaves, such as imitation , leads to tarnishing, where surface discoloration and diminish aesthetic and structural integrity over time. The 20th-century "acid paper" crisis highlighted these issues, with approximately 80% of books in library collections produced before the 1980s on acidic wood-pulp paper at risk of rapid deterioration due to inherent acidity from and pulping processes. This has resulted in widespread embrittlement, affecting handling and readability in archives worldwide. Conservation strategies focus on mitigating these effects through alkaline deacidification treatments, such as those using nanoparticles, which neutralize acids and deposit a protective alkaline reserve to buffer against future . Optimal climate control in storage environments—maintaining temperatures of 18-22°C and relative humidity at 40-50%—prevents mold proliferation and slows chemical degradation without promoting over-drying. Non-invasive metering, using tools like the Abbey pH Pen, allows for quick assessment of acidity levels on surfaces to guide targeted interventions. In case studies of sized preservation, enzymatic cleaning, such as with for residues, has effectively removed associated stains like mold from historical fabrics. While effective, strength loss varies; one study on using enzymes reported approximately 7% loss in warp direction, less than more invasive methods. These approaches, applied to textiles, demonstrate reduced damage and improved long-term stability without compromising historical integrity.

Modern Sizing Agents and Sustainability

Since the early , with continued advancements in the , the sizing industry has shifted toward bio-based agents to address environmental concerns, with derived from shells emerging as a key sustainable alternative for warp sizing. enhances weaving efficiency by reducing yarn breaks and forms a wash-resistant layer without requiring extensive wash-out processes, thereby minimizing generation and enabling closed-loop systems in production. For example, in the , Candiani introduced Kitotex®, a patented -based sizing agent that replaces synthetic PVA, enabling eco-friendly production with reduced wash-out needs. Its biodegradability supports enzyme-assisted removal during , further lowering ecological impacts compared to synthetic polymers. Similarly, , sourced from renewable , serves as an effective for and textiles, improving mechanical strength—such as an 18% increase in tensile index for —and barrier properties while replacing petroleum-based plastics. These agents promote by utilizing as a and reducing , with applications in eco-friendly processes that cut use by up to 25 times. Efforts to replace per- and polyfluoroalkyl substances (PFAS) in grease-proofing have led to fluorine-free synthetic alternatives, particularly for paper packaging and textiles. These include bio-based coatings like waxes, dispersions (e.g., styrene-acrylate copolymers), and ORMOCER® hybrid materials, which achieve comparable oil and grease resistance ratings without persistent environmental contaminants. For instance, over 25 fluorine-free formulations now match PFAS performance in food contact papers, supporting grease resistance while being biodegradable and compliant with regulatory pressures. In textiles, these alternatives enhance water and oil repellency in fabrics without the bioaccumulative risks of PFAS. Sustainability advancements also include reduced water consumption through innovative application methods, such as foam-based sizing and finishing in textiles, which can cut usage by approximately 30% compared to traditional wet processes by minimizing liquor ratios. This approach shortens drying times and lowers energy demands, aligning with principles where recyclable bio-based sizes— like modified starches and —facilitate easier recovery and reuse in textile loops. Enzymatic modifications of starches further boost biodegradability for surface sizing; for example, treatment with β-amylase or pullulanase optimizes and molecular distribution, increasing tensile strength by up to 93.9% while ensuring the agent breaks down naturally post-use. These processes are cost-effective and suitable for food-contact applications, reducing effluent . Regulatory developments underscore the push for greener agents, with the European Union's REACH framework issuing an Assessment of Regulatory Needs (ARN) in August 2023 for and its derivatives, commonly used in paper sizing, prompting harmonized classifications and potential phase-out due to and environmental risks. This aligns with broader trends driving market growth; the global sizing agents market reached approximately USD 3.95 billion in 2024, projected to expand at a 4.95% CAGR through 2032, fueled by demand for bio-based and low-impact technologies. Digital monitoring tools, including IoT sensors, are increasingly used in processes for optimization, minimizing overuse and waste while supporting real-time adjustments for efficiency. Challenges persist in balancing performance with low volatile organic compound (VOC) emissions, as traditional synthetic sizes often release VOCs during application and drying, contributing to air pollution in textile and paper mills. Sustainable alternatives like bio-based agents address this by inherently producing fewer emissions, though formulation must ensure adhesion and durability without compromising strength. Life-cycle assessments of renewable sizing options demonstrate 20-40% carbon footprint reductions compared to fossil-based counterparts, primarily through lower energy in production and biodegradation phases, supporting broader industry transitions to renewables. These evaluations highlight the need for integrated strategies to scale such innovations while maintaining economic viability.

References

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  6. https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1029&context=textiles_facpub
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  10. https://www.perfectpapercompany.co.uk/blogs/news/basic-breakdown-sizing
  11. https://www.textileschool.com/1080/sizing-operation-for-textiles/
  12. https://carbontrail.net/glossary/sizing-in-textile-process/
  13. https://eu.winsornewton.com/en-row/blogs/guides/sizing-canvas
  14. https://www.gildedplanet.com/howtogoldleafwithoilsize.html
  15. https://www.alternativephotography.com/sizing-or-subbing-papers/
  16. https://www.michelman.com/markets/reinforced-plastic-composites/fiber-sizing/
  17. https://www.conservation-wiki.com/wiki/BPG_Sizing_and_Resizing
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