sizings

Sizings are substances applied to fibers, papers, or textiles to modify surface properties, processing performance, or final product characteristics. They are typically formulated as aqueous emulsions or solutions and applied during manufacturing or finishing.

In papermaking, sizing is used to control the interaction between the paper and liquids. Internal sizing is added to the pulp before sheet formation to reduce ink absorption and improve print quality, while external or surface sizing is applied to the finished sheet to enhance water resistance and surface strength. Historically rosin-based sizes combined with alum were common, but modern papermaking uses synthetic sizes such as alkyl ketene dimer (AKD) or alkenyl succinates, along with starch-based or polymeric additives.

In textiles, sizing refers to a protective coating applied to warp yarns to reduce friction and breakage during weaving and to improve loom efficiency. Common sizings include starch, modified starches, carboxymethylcellulose, polyvinyl alcohol, and various acrylic or polymer emulsions. Desizing, the removal of sizing before finishing, often employs enzymes (for starch-based sizes), acids, or washing steps.

Outside these core uses, sizings can be applied in coatings and composites to tailor surface energy, adhesion, or barrier properties. The choice of sizing depends on substrate, processing conditions, and end-use performance goals, and may involve considerations of environmental impact and downstream wastewater treatment.