go

DYEING AND CALICO PRINTING.

Soda or Potash Vat.

By boiling io lbs. of indigo in a solution of 4 lbs. of caustic soda or potash,and adding 2 lbs. of feathered tin, or 3 lbs. of tin crystals, the indigo isdeoxidised by the strong affinity of the tin for the oxygen. The ordinarymethod of fermentation is, however, to be preferred, as a larger quantity ofwork can be got through. But the soda vat is preferable for light blues, asa brighter colour is obtained than by the woad vat, while larger quantities ofgoods may be coloured more easily. Potash should be employed for linen andcotton.

A Decomposed Vat.

A decomposed, or, as it is termed, a “ sick ” or “ green ” vat may be knownby its dark colour and freedom from odour, and more certainly by the additionof lime, bran, madder, and soda, or of woad. If, after several hours, the vatis restored, it may be worked with care as a new vat.

Applications of the Woad Vat.

The applications of the woad vat, as well as many pradtical recipes relatingto the colouring of wool, we shall, for facility of reference, include in thischapter.

Indigo-Blue on Wool for Topped Hosiery.

100 lbs. of wool are coloured with 4 lbs. of Guatemala or 3 lbs. of Bengalindigo, in the woad or soda vat. There is then prepared by. boiling for a fewminutes 5 lbs. of cudbear or 8 lbs. of orchil paste, adding to the mixture 1 lb.of soda, or an equivalent quantity (about one pail) of urine. The beck mustbe cooled to 170° F. before the wool can be entered. It should be handled fortwenty minutes, taken out, rinsed, and dried. 3 ozs. of aniline purple dissolvedin half a pint of alcohol can be used instead of the cudbear. The shade pro-duced is very pretty, but ought never to be used for mixed goods, which haveto be bleached, as it runs into whites. The cudbear, too, is affedted bysulphuring.

Dark Blue, for Wool for Broadcloth.

A healthy woad vat is employed for this colour. The wool is handledslowly for one hour, then removed; after two hours it can be again dippeduntil it has acquired the desired shade. Enough indigo should be added tothe vat to colour the wool in three immersions ; that is, about 10 lbs. of goodindigo to 100 lbs. of wool. The wool may with advantage be taken througha warm bath containing 2 lbs. of sulphate of copper; this additional immersionrenders the colour faster in fulling. A dark blue, very common in the market,is topped with camwood or red sanders, the latter being boiled on thecoloured wool.

Topped Logwood Blue.

Dip in the blue vat and then rinse. Boil the wool thus dipped for onehour in a kettle containing 10 lbs. of alum, 2 lbs. of crude tartar, and i£ lbs.of sulphate of copper. Remove and cool. To some fresh water add 5 to 10lbs. of logwood (according to the shade required, and the quality of thelogwood) in a bag. Boil, and then cool the kettle to iyo° F. The wool maynow be entered and handled slowly; in one hour it may be cooled, rinsed, andswitched for drying.