Dyeing, Printing And Finishing

Dyeing

The most commonly used processes for imparting color to cotton are piece dyeing and yarn dyeing.

In piece dyeing, which is used primarily for fabrics that are to be a solid color, a continuous length of dry cloth is passed full-width through a trough of hot dye solution. The cloth then goes between padded rollers that squeeze in the color evenly and removes the excess liquid. In one variation of this basic method, the fabric, in a rope-like coil, is processed on a reel that passes in and out of a dye beck or vat.

Yarn dyeing, which occurs before the cloth is woven or knitted, is used to produce gingham checks, plaids, woven stripes and other special effects. Blue dyed warp yarns, for example, are combined with white filling yarns in denim construction

Printing

Printing colored designs on cotton cloth is similar to printing on paper.

Long runs of the same fabric design are produced on a roller print machine operating at speeds between 50 to 100 yards a minute. As many as of 10 different colors can be printed in one continuous operation.

A typical printing machine has a large padded drum or cylinder, which is surrounded by a series of copper rollers, each with its own dye trough and doctor blade that scrapes away excess dye. The number of rollers varies according to the fabric design, since each color in the design is etched on a separate roller. As the cloth moves between the rotating drum and rollers under great pressure, it picks up color from the engraved area of each roller in sequence. The printed cloth is dried immediately and conveyed to an oven that sets the dye

Finishing

Finishing, as the term implies, is the final step in fabric production. Hundreds of finishes can be applied to textiles, and the methods of application are as varied as the finishes.

Cotton fabrics are probably finished in more different ways than any other type of fabrics. Some finishes change the look and feel of the cotton fabric, while others add special characteristics such as durable press, water repellency, flame resistance, shrinkage control and others. Several different finishes may be applied to a single fabric.