474

DYEING AND CALICO PRINTING.

employed which contains the elements of the red mordant: after ageing, thepiece is vatted, next washed in a running stream, and after that dyed inmadder, the result being the produdtion of a red pattern on a blue ground.

These instances prove the great variety of patterns which can be produced.The details of these operations are entirely matters of practice, requiringvery nicely adjusted mechanical arrangements. The following are receiptsfor different resists :•—

For Deep Blue. —Water, 4 litres ; sulphate of copper, 1-25 kilos.; acetateof copper, 500 grms.; nitrate of copper, 875 grms.; alum, 240 grms.;pipe-clay, 2-125 kilos.; calcined starch, 1-25 kilos.

For Medium. Blue. —Water, 4 litres; sulphate of copper, 500 grms.;acetate of copper, 250 grms.; nitrate of copper, 500 grms.; alum,240 grms.; pipe-clay, 2 kilos.; calcined starch, 1 kilo.

Red-Resist, so-called Lapis. —Red liquor, sp. gr. 1-07, 12 litres; Senegalgum, from 2 to 3 kilos.; pipe-clay, 4 to 6 kilos.; olive oil, 1 kilo.;sulphate of copper, 1 kilo.; nitrate of copper, 500 grms.; sal-ammoniac, 1-5 kilos.

White Lapis. —No. 1 : Lime juice at a sp. gr. of 1-109, 5 litres ; thickenedlime juice, thickened with 1-5 kilos, of gum upon 2 litres,. 1-5 litres;sulphate of copper, 1 kilo.; pipe-clay, 3 kilos. No. 2: Water,2 litres; sulphate of zinc, 1 kilo.; pipe-clay, 725 grms.; gum Senegal,500 grms.; solution of nitrate of copper, sp. gr. 1-52, 0-12 litre.

For White Under Mordants, and for Blue Contours. —Caustic sodasolution, sp. gr. 1-070, 8 litres; arseniate of potassa, 3-5 kilos.;corrosive sublimate, 500 grms.; pipe-clay, 3 kilos,; gum Senegal,1-5 kilos.

The so-called discharge method is in many respedts rather inconvenient;it does not admit of very finely engraved patterns; and it requires very strongvats to prevent the running of the discharges. The application of the latteris always preceded by dyeing the goods uniformly blue, the strength of thevats being of very little importance in this process. The employment of dis-charges is based upon the property of energetic oxidising substances,whereby the indigotin is converted into soluble isatin. The most generallyapplied discharge is chromic acid, but since that substance cannot be used ina free state, because it will be immediately adted upon by the thickener, whichwould convert it into chromic oxide, a circuitous process is used. Upon thewoven tissue bichromate or neutral chromate of potassa is padded, and whendry there is printed on the pieces a composition, chiefly made up of an acid,whereby the chromic acid is set free; the strength of the chromic acidsolution must be regulated according to the intensity of the blue colour pre-viously imparted to the cloth. A medium blue requires an almost saturatedsolution of the chromate ; the goods padded with bichromate cannot be driedin the open air, at least not by diredt exposure to sunlight, because that wouldcause the destrudtion of much of the indigo. Oxalic acid is very commonlyemployed as the chief constituent of the paste intended to set the chromicacid free ; it is thickened with gum, dextrin, or starch, to which some pipe-clay is added ; in some instances nitric, sulphuric, or tartaric acid is applied.The decolouration of the portions of the blue colour of the cloth, where theacid composition has been fixed, is almost instantaneous ; the goods are next