1835.] 



Gdico- Printing . 



17 



8. Buff from Iron. — This pleasing 

 colour is merely the peroxide of iron. 

 A mixture of sulphate of iron and 

 acetate of lead is printed on the cloth, 

 constituting in fact, sulphate and 

 acetate of iron together. After ex- 

 posure to the air for a considerable 

 time, to produce as large a deposit as possible upon the 

 cloth, the iron is farther precipitated by immersing the 

 piece in thick lime water, or in a mixture of caustic potash 

 and lime. A portion of black oxide is thus thrown down 

 along with the red, which speedily changes in the fresh 

 water and air to which it is afterwards exposed. 



9. Manganese Bronze. — A solution 

 of sulphate of manganese is printed on 

 the cloth by the copper roller. When 

 dry, the piece is passed through a 

 strong caustic alkali, and then allow- 

 ed to fall into a vessel containing chlo- 

 ride of lime. This converts the man- 

 ganese into sesquioxide, which has a strong affinity for cotton . 





10. China Blue. 

 fixed upon cotton in a 



Indigo may be 

 variety of 



ways. By heating it with orpiment 

 and caustic potash, it is deoxidized 

 and dissolved. If gum-senegal or 

 roasted starch be not dissolved in the 

 solution, it forms what is called 

 pencil blue, which may be printed upon cloth by means of 

 the copper roller, or by the block from a sieve of a peculiar 

 kind. Applied in either of these ways, the indigo soon re- 

 covers its blue colour, and being no longer soluble, it 

 remains upon the cloth, while water removes the substances 

 with which it was mixed. 



By another process, indigo in the blue state is mixed 

 with orpiment in a solution of sulphate of iron, and de- 

 oxidized after being printed on the cloth, by alternate im- 

 mersions in lime and copperas. It is known that indigo 

 in the deoxidized or white state, is soluble in alkalies, 

 forming a yellow coloured solution. This solution deposits 

 its deoxidized indigo on the cloth by mere contact. In this 



vol. i. c 



