382 The. Art of Dyeing. 



obtained ; but the pieces which are likewise dyed in suc- 

 cession come out light-yellow, and amount in weight only 

 to 10 loths (4 - 68 oz.). Quercitron bark, therefore, contains 

 one colouring matter which dyes dark-yellow, and another 

 which gives a light-yellow colour. 



Hence, it follows, that a dyeing matter can be deprived 

 of its whole colouring matter only by repeated dyeing. 

 Some solutions contain still a quantity of colouring matter 

 in which very saturated and dark colours will be produced, 

 which are mostly formed by an excess of colouring matter. 

 That this colouring matter may not be lost, other pieces 

 destined to be dyed of the same colour may be dyed in these 

 solutions, and may afterwards, in a new solution, receive 

 the p roper saturation. 



As the dyeing materials, madder, logwood, fernambuc, 

 &c, are to be considered as fibres of plants which, by boil- 

 ing in water and in dyeing the calico, lose their colour, so 

 the action of these vegetable fibres upon the colouring 

 matter combined with them, requires some attention. 

 Most of them retain their colouring matter so strongly, 

 that it is impossible to deprive them of it by pure water 

 alone. Thus, logwood may be boiled from 20 to 30 times, 

 with 6 times its quantity of distilled water, without being 

 completely taken up, and the remaining fibre gives a 

 reddish-brown colour to potash ley. 



Calico, impregnated with the alum mordant, takes up 

 the colour more rapidly with the assistance of water. It 

 takes immediately from the water the dissolved colouring- 

 matter, and converts it into pure water, which can again 

 dissolve new colouring matter, which the calico again 

 takes up. 



In this way, a peculiar exchange frequently takes place. 

 If the mordanted calico is not completely deprived of all 

 uncombined superfluous mordant, or if the dyeing solution 

 possesses the property of taking up the mordant from the 

 calico and dissolving it, the coloured fibre of the dyeing- 

 material is mordanted, while the mordanted cotton fibre is 

 dyed. 



Both fibres divide themselves in the mordant and in the 

 dye, to the great annoyance of the dyer. Hence, the 

 madder employed for the Turkey-red dye is almost as dark 



