Last updated on July 14th, 2023 at 01:37 am
Textiles may be dyed at any stage of their development from fibre into fabric or certain garments. Stock dyeing is done in the fibre stage, Top dyeing in the combed wool sliver stage and Yarn dyeing is done after the fibre has been spun into yarn.
Definition of Stock Dyeing
Stock dyeing refers to dyeing a staple fibre before it is spun. There are two methods. The older and widely practiced procedure is that of removing the packed fibre from the bales and then packing the stock in large vats and circulating dye liquor through the mass of fibre at elevated temperatures.
The newer method, bale dyeing, which is applicable to wool and all types of manmade fibres, is that of splitting the bale covering on all six sides, placing the entire bale in a specially designed machine (covering and straps need not be removed), and then forcing the dye liquor through the bale of fibre. This latter method obviously saves time and labor costs.
Although the dye liquor is pumped through the fibre in large quantities, there may be areas where the dye does not penetrate completely. However, in subsequent blending and spinning operations, these areas are so mixed with the thoroughly dyed fibre that an overall even color is obtained. In stock dyeing, which is the most effective and expensive method of dyeing, the color is well penetrated into the fibres and does not crock readily. Stock-dyed fibre does not spin as readily as undyed fibre because it loses some of its flexibility, but lubricants add in the final rinsing overcome most of this difficulty.
Definition of Top Dyeing
One step nearer to the finished yarn than stock dyeing is what is called top dyeing in the worsted industry. Top is wool that has been combed to take out the short fibres, then delivered from the combs in a ropelike form about 1.25” the top is wound on perforated spools and the dye liquor is circulated through it. Very even dyeing is possible with this method.
Definition of Yarn dyeing
When dyeing is done after the fibre has been spun into yarn, it is described as yarn dyeing. There are several methods of yarn dyeing. The purpose is to have the dyestuff penetrate to the fibres in the core of the yarn; this is similar to the penetration of the fibres in stock dyeing. Cloths made of dyed yarns are called yarn-dyed.
Yarn-dyed fabrics are usually deeper and richer in color. These fabrics intended for laundering must be quite colorfast, or bleeding could occur. The primary reason for dyeing in the yarn form is to create interesting checks, stripes, and plaids with different-colored yarns in the weaving process. Chambrays, for example are usually woven with a colored warp and white filling. Other combinations of different-colored yarns are checked gingham, shepherds check, plaid, seersucker, and heater mixtures.