CALICO, a species of cloth of cotton thread, manufactured formerly in the East Indies ; but now we have in this country established manufactories which equal those in the East. It is said that in this business, and in the printing of calicoes, there are 150,000 persons em ployed. Cotton, in its raw state, is im ported into this country, but calicoes are prohibited under the severest penal. ties.
Csirco-printing : the art of cloth-print ing or calico-printing : in other words, of dyeing in certain colours particular spots of the cloth, or figures impressed on it, while the ground shall be of a different colour or entirely white, affords perhaps the most direct and obvious illustration of the application of these principles. The mordant which is principally used in this process is the acetate of argil. It is prepared by dissolving 316s. of alum and llb. of acetate of lead in 81bs. of warm water. An exchange of the principles of these salts takes place : the sulphuric acid of the alum combines with the oxide of lead, and the compound thus formed being insoluble is precipitated, the acetic acid remains united with the argil of the alum in solution. There are added at the same time two ounces of the potash of commerce, and two ounces of chalk ; the principal use of which appears to be, to neutralize the excess of acid that might act on the colouring matter, and alter its shade.
The superiority of this acetate of argil as a mordant to the cheaper sulphate of argil of alum arises principally from two circumstances,—from the affinity between its principles being weaker, in conse quence of which the argil more easily se. parates from the acid, and unites with the cloth and the colouring matter : and 2dly, from the acetic acid disengaged in the process not acting with the same force on the colouring matter as the sul phuric acid would do. The acetate being also very soluble, and having little ten dency to crystallize, can be more equally mixed and applied. The discovery of this mordant, so essential in the art of calico-printing, was altogether accidental, or rather empirical. The recipes of the calico-printers were at one time very complicated : different articles were from time.to time omitted or changed, until at
length the simple mixture of alum and acetate of lead was found to answer as a mordant, equally with compositions more complicated ; and even after its discovery, its operation for a time was far from be ing understood by the artist. The mor dant thus prepared is thickened with gum or starch ; or in this country, within these few years, with the mucilage pre pared from lichens scalded and boiled with a little potash. It is applied by wooden blocks, or stamps, to the parts of the cloth on which the figures cut in the stamp are designed to be impressed, we by a pencil, if more delicate lines are to be traced. The cloth is afterwards dried thoroughly, is washed in warm water to remove the mucilage and the superfluous mordant, and is then dipped in the dye colour, supposed to be an infusion of madder ; the whole is dyed, but the parts which have been impreg nated with the mordant receive a brighter colour .than the part which has not : the colour too of the former is permanent, while that of the latter is fugitive. It is discharged by subsequent boiling with •substances having a weak attraction to the colouring matter, principally with bran, and by exposure on the field, re peating these alternately. The ground of the cloth is thus at length rendered white, while. the colours of the parts on which the mordant has been impress ed, representing of course the design on the stamp, remain with little or no alter ation.
Sometimes, after the whole cloth has been permanently dyed, by having been impregnated with the mordant, the colour is discharged from certain parts, by stamping these with a weak acid liquor : after being washed, these are again stamped, either with the same or with a different mordant, and dyed with differ ent materials ; and thus the most diffi cult kind of cloth printing is effected, where the ground is coloured, and at the same time impressed with a design in different colours. By combining these methods too, and by dexterously applying to different parts of the cloth different mordants, by stamps adapted to each other, to as to form a regular design, different colours are impressed, either on a white or coloured ground.