362

DYEING AND CALICO PRINTING .

up to a more or less fine powder; in the state of decoCtion, made either withwater only or with that fluid acidulated or rendered alkaline.

Carminic acid, although soluble in water, does not fix itself to any kind offibre, whether animal or vegetable : it dyes cotton, mordanted with aluminaonly, amaranth-red, but when oxide of tin is simultaneously present asmordant a flat and meagre scarlet-red is produced; with iron mordants thecolours produced are grey, violet-grey, or greyish-black, according to thestrength.

Wool mordanted with preparations of tin is dyed a brilliant scarlet, of apeculiarly bright hue, and not readily obtainable by any other dye ware orupon any other fibre. The lac-dye of Messrs. Brooke, Simpson, and Spilleryields, upon wool, a colour almost as bright and beautiful.

Amaranth-red, red, violet-red, scarlet, and red-purple are produced bycochineal in its entire or ground-up state. Ammoniacal cochineal is used formauve and amaranth-purple, and is, moreover, an ingredient of some compo-site colours. The dyeing of mordanted cotton, and all the operationspertaining thereto, are for cochineal the same as for madder.

Since carminic acid is rather a strong one, it has the power of dissolvingtemporarily some of the aluminous mordant, if too much of the ware ispresent along with the mordanted tissue : this would tend to weaken the colourintended to be obtained, and, moreover, the lake thus set free in the dye-beckmight become fixed upon portions of the tissue intended to remain white; forthis reason the cochineal is either added in two portions to the dye-bath, orthe cloth is dyed first in a partly-exhausted bath, to which next a fresh portionof cochineal is added. The temperature of the first bath is only 40°; the secondis brought to boiling ; the addition of some nut-galls to the bath is intended togive fastness to the colour, as well as to prevent the corroding action of thecarminic acid. Probably an excess of carminic acid forms a soluble acidcarminate, which during the dyeing process is rendered neutral and insoluble,and thus fixed upon the white portions of the tissue. The goods, on beingtaken from the dye-beck, are so slightly soiled that after a thorough rinsing inwater and a bran-bath the white is perfectly restored. The colours thus ob-tained are not fast, and do not stand washing with soap nor the a&ion ofeither acids or alkalies.

Cochineal is very rarely, if ever, at all applied to mordanted cotton or calicotissues since the introduction of aniline colours ; but its use as a steam-colour upon cotton, and in dyeing and printing wool and silk tissues, is veryextensive.

Deep Rose-Red for Steam-Colour .—1 litre of a decodtion of cochineal madewith 250 grms. of the grain to the litre; 2 litres of water; 0*5 litre of redliquor, at io° B. (sp. gr. 1*075); 40 grms. oxalic acid ; 1*75 kilos, gum.

Application-Red .—2 litres of a decoCtion of cochineal made with 375 grms.to the litre ; 25 grms. tragacanth gum ; 185 grms. pink salt, prepared with1 litre of nitro-muriate of tin mixed with a hot and saturated solution of500 grms. of sal-ammoniac.

Cochineal-lake is employed for the purpose of printing, being fixed by meansof albumen. Cochineal is fixed upon wool and silk by means of alum andcream of tartar, whereby carmine shades are obtained ; for scarlet, tin crys-tals are added.