trough is a steam pipe b, perforated at intervals, by which the requisite heat for the dyeing operation is raised and maintained. Sloping upward from the steam pipe is a perforated diaphragm of iron or midfeather c, and mounted on a strong framework over the trough is the winch D, which by its revolutions, effected by spur wheels, keeps the cloth moving down and up continuously into and out of the trough. A peg rail e runs along the length of the trough which keeps the pieces from becoming entangled in their cuurse. The figure shows the course of a chain of pieces being dyecl on the endless system, in which about twenty-five pieces are sewn together, and passed in a spiral form up and down from end to end and back again, to go over the same course continuously throughout the entire time necessary for completing the operation. Another and more common method of arranging the pieces in the dye- vat is to pass two pieces, tied together end to end, over the winch between each separate pair of pegs, in which case the pieces revolve between the same pegs throughout the operation. Whichever method is followed, the opera tion and results are precisely the same. The required quantity of cold water is admitted into the trough, the pieces are arranged on the winch, the dye-stuff is intro duced, and the machinery set in motion. Steam is then turned on, and the liquid is heated gently and gradually till it reaches about 180 Fahr. The process is continued for from an hour and a quarter to about two hours, during which time great care is taken to maintain the temperature arrived at, and to keep the pieces in constant circulation in and out of the vat. On the completion of the operation steam is shut off, and the pieces are rinsed through cold water, after which they are carefully and repeatedly washed. Fig. G presents a sectional view of an apparatus devised by Messrs Mather and Platt for loose washing after
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FIG. 6. Matlit r and Platt s "Washing Apparatus.
In this machine there arc two water-boxes a, I, and three bowls c, d, e, which are mounted horizontally in relation to each other. The central large bowl d, instead of being circular, has an irregular curved outline of alternate elevations and depressions. Against this irregular-shaped bowl the two side bowls c and e are made to press, and they move back and forward, following the irregular outline, pressed by powerful springs / acting on the axes on which they arc mounted. They have thus a rubbing action in addition to their motion of revolution, an arrange ment which produces a kind of flapping and squeezing action analagous to hand-washing.
Clearing.—At this point the dyed calicoes present a very unpromising appearance, the mordanted portions which have absorbed the dye being dull and heavy in colour, while the whites have a sickly pink aspect. The operations of clearing are necessary to remove all the dye-stuff which is loosely attached to the whites, and to develop and brighten the tints of dyed pattern. A variety of processes are pursued to accomplish this object, but in all the action of soap and some " chemick" or chlorine solution plays the principal part. The soap used must be free from all excess of alkali, and besides its detergent action it is supposed to be decomposed and give up part of its fatty acid to the lake formed by the mordant and the dye-stuff. The processes for clearing such calicoes as here described are as follows. After washing out of the dye- beck the goods are passed into a soaping beck, very similar in construction to the dye- beck, but surmounted with a pair of squeezing rollers instead of the winch of the dyeing apparatus. In this they are treated with a hot solution of soap ; they are then washed out, squeezed, and again soaped, the second time at a higher temperature than the first. After another washing they are " chemickcd " in a weak chlorine solution, prepared by mixing chloride of lime with soda ash, with excess of soda, and from that a final washing in pure water should leave the goods clear and bright, ready for the finishing operations they receive in common with all other styles.
The reds and pinks produced by an alumina mordant with madder or artificial alizarin receive a different treat ment. Mr Charles Dreyfus of Manchester, in a paper of great practical value communicated to the Society for the Promotion of Scientific Industry,[1] says of these colours : "They were some time ago dried and steamed; by the steaming a further quantity of colouring matter Avas com bined to the mordant, and the shades thus obtained were fuller than if the goods had not been steamed. Now, instead of steaming only, the goods are passed through preparations the basis of which are fatty acids or fatty or resinous compounds : they are steamed after this prepara tion. I can speak highly of the good results obtained with some of these preparations, both as regards shade and saving of colour. The only difficulty is to obtain a good white : this can be overcome by careful and proper treatment of the goods. For reds and pinks there is a special and extra operation, commonly called the cutting. It consists in passing the goods soaped and well washed through diluted nitromuriate of tin ; the reds and pinks seem to be destroyed, becoming of a deep orange, but the subsequent soaping brings out again the brilliancy of the shade."
The processes above described are followed, with only modifications as to strength of mordants and the clearing operations, for the printing of calicoes with the madder pre parations, garancin, garanceux, and alizarin. The colours produced by these substances are as brilliant as nadder colours, but they do not possess such fastness. On the other hand, the whites are not deeply stained in the dye-beck, and they generally require only a simple padding through a weak chlorine solution, and washing to clear the whites and pre pare the goods for finishing. Some garancin and alizarin shades stand soaping well, and are improved in tone by such a treatment. Artificial alizarin and madder extract are now however chiefly used as steam colours, and to such perfec tion has printing in that style attained that the dye-house has been abandoned altogether in certain Continental establishments. The retention of dye-colour printing may now indeed be looked on as a question of comparative expense, which is determined chiefly by the price of fuel.
belongs rather to the province of Dyeing than to calico- printing ; but as patterns are produced on it by means of discharges, it is necessary to include a notice of it under
the head of dye colours. It is obtained with madder,- ↑ Journal of the Society, vol. i. No. 3, Dec. 1874.
