TANNING. 201 



If some parts of the yellow be covered over with 

 the indigo liquor, applied with a pencil, it will be 

 converted into green. By the indigo, also, any 

 parts that are required to be blue may be pencilled. 



If, instead of quercitron bark, the cloth printed 

 with the three mordants just mentioned be dyed 

 with madder, then the colours exhibited will be 

 red, brown or black, and purple. 



Other processes are still more complicated when 

 a great number of colours are required. New 

 mordants are applied to parts of the pattern alrea- 

 dy printed, and the cloth again dyed, by which 

 those parts only receive a new colour. 



Sometimes the dye stuff and the mordant are 

 mixed together in the first instance, and printed on 

 the cloth, which is a great saving of time and ex- 

 pense ; but the colours thus produced on the cloth 

 are not permanent: washing, or even exposure to 

 the air frequently destroys them. 



TANNING. 



Tanning is the art of converting the raw skins of 

 animals into leather. 



The skin is composed chiefly of two parts, a thin 

 white elastic layer on the outside, which is called 

 the epidermis, or cuticle ; and a much thicker layer, 

 composed of a great many fibres, closely inter- 

 woven, and disposed in different directions: this 

 is called the cutis, or true skin. 



The epidermis is that part of the skin which is 

 raised in blisters. It is easily separated from the 

 cutis by maceration in hot water. It possesses a 

 very great degree^of elasticity. It is totally inso- 

 luble in water and alcohol. Pure fixed alcalis dis- 

 solve it completely, as does lime likewise though 

 slowly. 



