Stock dyeing refers to the dyeing of the fibers, or stock, before it is spun in to yarn. It is done by putting loose, unspun fibres in to large vats containing the dye bath, which is then heated to the appropriate temperature required for the dye application and dyeing process.
Stock dyeing is usually suitable for woolen materials when heather like color effects are desired. Wool fibre dyed black, for example, might be blended and spun with un-dyed (white) wool fibre to produce soft heather like shade of grey yarn.
It is done by putting loose, un-spun fibers into large vats containing the dye bath, which is less than heated to proper temperature. From 500 to 3000 pounds (227 to 1364 kgs.) of fiber are dyed at one time, and the average is about 1000 pounds (454 kgs.)
Tweed fabrics with heather like color effects such as Harris Tweed are examples of stock dyed material. Other examples include heather like colours in covert and woolen cheviot.
Process of Stock Dyeing
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.
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