CALICO-PRINTING; 4S7 



Calico-printing. 



THIS ingenious art consists in dyeing cloth with certain colours 

 and figures upon a ground of a different hue; the colours, when 

 they will not take hold of the cloth readily, being fixed to them by 

 means of intennedes, or mordants, as they were formerly called, 

 constituting materials that have a chemical affinity or attraction for 

 both the materials that form the colour, and the cloth to which the 

 colour is to be applied. It was lung ago supposed that these inter, 

 ruedos corroded their way into the interior of the cloth, and 

 carried the colouring matter along with them, and it was on this 

 account they were called mordants ; but since the science of che- 

 mistry has been better studied and understood, it has been suili. 

 ciently ascertained, that they only act or hold the dye and the 

 cloth together, by a mutual affinity or attraction. 



The mordant which is principally used in the general process is 

 a preparation of alum, called in the new nomenclature acetate of 

 argil. It is prepared by dissolving 3lhs. of a'um and lib. of ace. 

 tate of lead in 8lbs of w arm water. An exchange of the princi- 

 ples 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 arid that might act on the colouring matter and alter 

 its shade. 



The superiority of this acetate of argil as a mordant to the 

 cheaper sulpliat of argil or alum, arises principally from two cir. 

 cumstances ; from the affinity between its principles being weaker, 

 in consequence of which, the argil more easily separates from the 

 acid, and unites with the cloth and the colouring matter; and, 

 2dly, from the acetic arid disengaged in the process not acting with 

 the same force on the colouring matter as the sulphuric acid would 

 do. The acetate being also very soluble, and having little ten. 

 deney 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 arti v 



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