To perform all the operations in one bath the acid bath is made with from 3 to 4 lb. sulphuric acid, and the wool is treated therein for thirty minutes at 170° F., until all the acid has been absorbed. Then the bath is allowed to cool down to 70° or 80° F., the clear bleaching powder solution is added, the goods are re-entered, and the bath is heated to the boil. When all the chlorine has disappeared add the dye-stuff, and dye as directed above.
In printing on wool the chlorination of the wool is a most important preliminary operation. For this purpose the cloth is passed for fifteen minutes at 170° F. through a bath containing 3/4 oz. sulphuric acid per gallon of water. Then it is passed through a cold bath of 3/4 oz. bleaching powder per gallon of water, after which the cloth is rinsed and dried and is then ready for printing.
Another method of chloring the wool is to pass the goods through a bath made with 100 gallons of water, 2 gallons hydrochloric acid and 2 gallons bleaching powder solution of 16° Tw. As some chlorine is given off it is best to use this in a well-ventilated place.
CHAPTER III.
DYEING MACHINERY AND DYEING MANIPULATIONS.
Wool is dyed in a variety of forms, raw, loose wool; partly manufactured fibre in the form of slubbing or sliver; spun fibres or yarns, in hanks or skeins and in warps, and lastly in the form of woven pieces. These different forms necessitate the employment of different forms of machinery and different modes of handling, it is evident to the least unobservant that it would be quite impossible to subject slubbing or sliver to the same treatment as yarn or cloth, otherwise the slubbing would be destroyed and rendered valueless.
In the early days all dyeing was done by hand in the simplest possible contrivances, but during the last quarter of a century there has been a great development in the quantity of dyeing that has been done, and this has really necessitated the application of machinery, for hand work could not possibly cope with the amount of dyeing now done. Consequently there has been devised during the past two decades a great variety of machines for dyeing every description of textile fabrics, some have not been found a practical success for a variety of reasons and have gone out of use, others have been successful and are in use in dye-works.
Hand Dyeing.--Dyeing by hand is carried on in the simplest possible appliances, much depends upon whether the work can be done at the ordinary temperature or at the boil. Figure 10 shows round and oval tubs and a rectangular vat much in use in dye-houses. These are made of wood, but copper dye-vats are also made, these may be used for all kinds of material--loose fibre, yarns or cloth. In the case of loose fibre this is stirred about either with poles or with rakes, care being taken to turn every part over and over and open out the masses of fibre as much as possible in order to avoid matting or clotting together. In the case of yarns or skeins, these are hung on sticks resting on the edges of the tub or vat. These sticks are best made of hickory, but ash or beech or any hard wood that can be worked smooth and which does not swell much when treated with water may be used. The usual method of working is to hang the skein on the stick, spreading it out as much as possible, then immerse the yarn in the liquor, lift it up and down two or three times to fully wet out the yarn, then turn the yarn over on the stick and repeat the dipping processes, then allow to steep in the dye-liquor. This is done with all the batch of yarn that is to be dyed at a time. When all the yarn has been entered into the dye-bath, the first stickful is lifted out, the yarn turned over and re-entered in the dye-liquor; this operation is carried out with all the sticks of yarn until the wool has become dyed of the required depth. In the case of long rectangular vats it is customary for two men, one on each side of the vat, to turn the yarns, each man taking charge of the yarn which is nearest to him.
