Textiles

Aside from exploiting the effects achieved by using natural fibers, the only ways to introduce color into textiles are by printing or dyeing.

In textile printing, the dyes are dissolved in water. Thickening agents (e.g., starch) are added to the solutions to increase viscosity. The oldest method is block printing, usually from wooden blocks in which a design is carved. Stencil printing is done with the aid of paper or thin metal stencils. In silk screen printing, the design is formed on a silk screen, which then serves as a stencil. Most cloth is printed by roller printing. The printing area is engraved on a copper roller to form a recessed pattern (intaglio), which is coated with a color paste. The roller transfers the paste to the cloth.

Pattern dyeing uses two principal procedures: resist dyeing and mordant dyeing. In resist dyeing, a resist substance such as hot wax, rice paste, or clay is applied to those areas chosen to resist the dye and remain white. The cloth is then dyed and the resist is later removed. The technique is widely known in China, Japan, and West Africa, but is most often identified with Javanese batik. Tie dyeing is a resist technique in which parts of the cloth are tied with bast or waxed cord before dyeing. The dyeing is done quickly so the wrappings are not penetrated, and a negative pattern emerges. Many dyestuffs are not directly absorbed by fibers, so mordants or fixing agents are used that combine with the dye and fibers to make the color insoluble.

There are two main types of textile dyeing machines: in one type the dye solution is circulated through the fabric, which remains at rest; in the other, the fabric is passed through a stationary bath of the dye solution.