DYEING AND CALICO PRINTING. 317 



would be incomplete without some information respecting this style, 

 which still occupies the foremost rank in the printing art. 



To obtain prints of this important style, white calico, bleached with 

 especial care, is printed by engraved copper rollers with one or more 

 mordants, such as the pyrolignites or acetates of iron and alumina, which, 

 under the influence of " ageing " (to be presently noticed), are so decom- 

 posed or modified by the oxygen and moisture of the atmosphere as to 

 leave on the cloth either an insoluble oxide or a subsalt, and these become 

 the intermediate agent for fixing on the fabric the colouring matters 

 called alizarine or purpurine ; iron giving from a dark purple to a light 

 lilac, alumina from a dark red to a pink, and mixtures of the two mor- 

 dants a variety of chocolate tints. After the process of " ageing," the 

 pieces are passed through a hot solution of the double phosphates of soda 

 and lime, the arsenite and arseniate of soda or the silicate of soda, which 

 " dung substitutes " have completely superseded the use of cow-dung in 

 the process of " dunging," the object of which is to fix thoroughly the 

 mordant on the cloth, and to remove any excess that may have been used 

 without allowing it to fix itself on the white or unmordanted parts. By 

 the introduction of these dung substitutes and improved dunging vats, a 

 great saving of time, labour, and expense, has been effected, thousands of 

 pieces being now done in the same vat where formerly hundreds only 

 could have been treated. 



The pieces, after having been well washed, are ready for the dye-beck, 

 in which the mordants assume the colours for which they are adapted. 

 Here also a slight improvement has been made, the advantage of which 

 is a saving of time, the mordants becoming saturated with alizarine and 

 purpurine in one hour and a quarter, or with the colouring principles of 

 madder in two hours. After leaving the dye-becks, the pieces are tho- 

 roughly washed in the improved washing machines, but as the white 

 parts (or those not mordanted) are still soiled, and the colours dim, it is 

 necessary to place the pieces for half an hour into a rather strong soap 

 solution heated to 180°, by which the loose dye is removed both from 

 the white parts and those on which colour has been fixed. To finally 

 brighten the colours and completely clean the white portions, the pieces 

 are passed into a weak solution of a mixture called " chymic," or an alka- 

 line hypochlorite, of soda with a little sulphate of zinc, until the desired 

 effect is obtained ; but latterly this process has been improved by pass- 

 ing the goods rapidly into chymic and then through a steam chest. As 

 they have not yet, however, a commercial appearance, they further 

 undergo what is called " finishing," that is, the pieces are passed through 

 a solution of flour which has been fermented for several weeks, starch, 

 farina, &c, and then between rollers ; after which they are dried and 

 passed through calenders, the object of these last operations being to fill 

 up the interstices of the cloth and give it a glossy appearance. 



Though it is thought advisable to abstain here from entering into the 

 details of the numerous improvements which have found their way into 



