DYEING 



smoothness of Us surface, which should 

 therefore be preserved unimpaired. 



Cotton withstands the action of acids 

 better than flax or hemp, and is dif- 

 ficultly destroyed even by the nitric 

 acid. 



Of Wool. 



Wool is naturally covered with a kind 

 of grease called suint, which preserves it 

 from moths, so that it is not scoured until 

 it is about to be died or spun. In order 

 to scour wool, it is put for about a quar- 

 ter of an hour into a kettle containing a 

 sufficient quantity of water, mixed with a 

 fourth part of putrid urine, heated to such 

 a degree as the hand can just bear, and 

 it is stirred from time to time with sticks ; 

 it is then taken out and put to drain. It 

 is next carried in a large basket to a 

 stream of running water, where it is mov- 

 ed about until the grease is entirely sepa- 

 rated, and no longer renders the water 

 turbid ; it is then taken out, and again 

 left to drain. It sometimes loses in this 

 operation more than a fifth of its weight. 



The scouring should be carefully per- 

 formed, because the wool is thereby bet- 

 ter fitted to receive the dye. In this pro- 

 cess the volatile alkali of the urine unites 

 with the grease, and forms a kind of soap, 

 soluble in water. 



When wool is dyed in the fleece, its 

 filaments, being separate, absorb a larger 

 quantity of the colouring matter ; for the 

 same reason woollen yarn takes up more 

 than cloth ; but cloths themselves vary 

 considerably in this respect, according to 

 their degree of fineness, or the closeness 

 of their tfxture. The wool dyed in the 

 fleece is chiefly intended to form cloths 

 of mixed colours. 



For most colours wool requires to be 

 prepared by being boiled witli saline sub- 

 stances, principally with alum and tartar. 

 For some dyes wool does not require this 

 preparation, and then it must be well 

 washed in warm water, and wrung out, 

 or left to drain. 



The asperity of the surface of the fila- 

 ments of wool, and their disposition to ac- 

 quire a progressive motion towards their 

 roots, form an obstacle to the spinning of 

 wool, which is removed by impregnating 

 it with oil. This oil must be discharged 

 previous to the stuff', formed of the wool, 

 being dyed. For this purpose it is carri- 

 ed to the fulling mill, where it is beaten 

 with large beetles in a trough of water, in 

 which a particular kind of clay has been 



diffused; that, uniting with the oil, ren- 

 ders it soluble in the water. 



Of Silk. 



Silk is naturally coated with a sub- 

 stance, which has been considered as a 

 gum, to which it owes its stiffness and 

 elasticity ; that which is most commonly 

 met with contains, besides, a yellow co- 

 louring matter. Most of the purposes 

 for which silk is employed require that 

 both these substances should be remov- 

 ed, which is effected by scouring it with 

 soap. 



The scouring ought not to be so com- 

 plete for silks which are to be dyed, as 

 for those which are intended to remain 

 white, and a difference ought to be made 

 accarding to the colour the silk should 

 leave. 



This difference consists in the quantity 

 of soap employed; for common colours, 

 the silk is boiled for three or four hours 

 in a solution of twenty pounds of soap 

 for every hundred of silk, taking care to 

 fill up the kettle from time to time, 

 that there may be always a sufficient 

 proportion of fluid. The quantity of 

 soap is increased for those silks which 

 are to be died blue, and more especially 

 for those which are to be scarlet, cherry 

 colour, &c. because for these colours the 

 ground must be whiter than for such as 

 are less delicate. 



When silk is intended to be employed 

 white, it undergoes three operations : 

 First, the hanks of silk are kept in a so- 

 lution of thirty pounds of soap to the hun- 

 dred weight of silk, which ought to be 

 very hot, but not boiling. When the im- 

 mersed part of the hanks is freed from 

 the gum, they are turned upon the skein 

 sticks, that the parts not before immers- 

 ed may underg'o the same operation ; they 

 are then taken out of the kettle, and 

 wrung out according as the operation is 

 completed. 



In the second operation, the silk is put 

 into bags of coarse cloth, five and twenty 

 or thirty pounds in each bag, which is 

 called a boiling bag. In these bags it is 

 boiled for an hour and a half in a bath of 

 soap, prepared like the former, but with 

 less soap, taking care to keep the bags 

 constantly stirred, that those which touch 

 the bottom of the kettle may not receive 

 too much heat. 



The third operation is intended prin- 

 cipally to give the silk a slight cast, to 

 make the white more pleasing ; from 

 which it derives different names, such as 



