MORDANTS.

*

>

)

)

299

a second time, using 36 litres of dung for 900 metres length of cloth, leavingit for half an hour in the bath at a temperature of from 38° to 57 0 C.

The following example of the dunging of cloth for garancin work will givean idea of the a&ual operation as performed on the large scale and the in-gredients employed. Goods for garancin work are, after leaving the ageingroom, twice dunged;* for blacks, violets, purples, greys, catechu browns,reds, and puce browns the first dunging consists in passing the goods suc-cessively in two minutes’ time through three tanks provided with rollers,and containing:—First tank—Water, 1400 litres; chalk, 12-5 kilos.; cow-dung, 40 kilos, heated to 38° C. Second and third tank—Water, 2S00 litres ;cow-dung, 35 kilos.; quercitron, 11 to 14 kilos.cheated to about 82°. Thesecond dunging is performed in one tank large enough to hold 12 piecesof cloth at a time; it is left in the tank and its contents for half an hour at atemperature of about 63°. The tank contains:—Water, 1200 litres; dung,20 kilos.; quercitron, 6 kilos.; sumach^ 2 kilos. For brown only, black only,grey and brown together only, red and black together only, brown and blacktogether only, brown and catechu brown together only, brown and purpletogether only, the first dunging is performed in three tanks with rollers con-taining:—No. 1—Water, 1400 litres; cow-dung, 30 kilos.; chalk, 10 kilos.,heated together to 38°. Nos. 2 and 3—Water, 2800 litres; cow-dung, 25 kilos.;quercitron, 23-05 kilos., heated to 82° C. The second dunging for these coloursis performed also in a tank capable of containing 12 pieces of cloth at once, thecharge being:—Water, 1200 litres; cow-dung, 25 kilos.; quercitron, 10 kilos.The whole is heated to 74 0 , and the goods are left for half an hour. Forbrown and purples only a little less quercitron is taken. For garancin work thedunging may also be replaced by the use of silicate of soda, but in that casethe colours require a stronger chlorine treatment, about which more below.The use of a sal-ammoniac bath instead of dunging is only suitable whenaluminate of soda has been used as a mordant.

We now have to treat of the operation of dyeing with madder, an operationwhich requires, when performed on the large scale, very great and specialcare, and a very intimate knowledge of the conditions essential to obtain thefullest, brightest, most uniform, and fastest colours, while simultaneously thefullest utilisation and greatest possible exhaustion of the colouring matter ofthe dye-stuff has to be secured. On the small scale it is easy enough to dyewith madder a piece of previously mordanted and dunged cloth, since it is onlynecessary to keep the pattern (say 1 foot square) fully immersed in a bathmade up of 12 grms. of madder and 1 litre of water, while the temperatureis slowly raised to the boiling-point during the lapse of one hour’s time, carebeing taken to stir the mixture frequently in order to insure uniformity of thecolour. The colouring matters of the madder, while gradually dissolving inthe liquid contents of the dye-beck, combine with the mordants, formingcoloured lakes, the shade of which as well as the intensity depends uponthe quality and quantity of the metallic oxide fixed to the cloth. Whenit is desired to obtain on the large scale a certain shade of constantintensity (depth) the printer or dyer has to take into account a great numberof conditions which influence the desired result. Among these, for instance,

* Some printers dung all goods twice; first in what is called the “Dolly,” and then at ahigher temperature in the dung-beck.