DYEING. 



237 



Of Stuff*, that wool which has been spun in the yolk, and scoured 

 1> ~""V~*' afterwards, is much whiter than if scoured before being 

 spun. Whatever method is adopted, the scouring 

 should be performed with great care, as the wool is 

 rendered, by that operation, much fitter for receiving 

 the dye. 



1ST. The wool is dyed in the fleece, or before being 

 spun, chiefly when it is to be manufactured into cloths 

 of mixed colours, and it is dyed after being spun 

 when it is intended for tapestry. But it is most com- 

 monly dyed after it has been manufactured into cloth. 

 When wool is dyed in the fleece, its filaments being se- 

 parate, are in a situation for absorbing a greater pro- 

 portion of colouring matters than when it is spun, and 

 still more than when it is in the form of cloth ; but dif- 

 ferent woollen stuffs vary considerably in this respect, 

 according to their fineness and closeness of texture. 

 These circumstances taken in consideration with the 

 different qualities of dyeing ingredients, prevent us 

 from relying with implicit confidence on the processes 

 usually recommended. 



188. After wool has been spun and wove, it is sub- 

 jected to the oj>erations of felling an<\ fulling. Accord- 

 ing to the observations of M. Monge, the fibres of wool 

 consist either of a great number of small lamina over- 

 lapping one another from the root to the extremity, or 

 of a series of annular concretions, like the horns of ani- 

 mals, gradually decreasing in diameter towards the 

 point. From this structure of the woolly fibre, if a hair 

 be held with one hand by the root, and drawn between 

 the thumb and finger of the other hand, scarcely any 

 friction or resistance is perceived; but if it be drawn in 

 like manner, in a contrary direction, a tremulous mo- 

 tion is distinctly felt, accompanied with a sensible gra- 

 ting noise. By this conformation of the fibre, a hair 

 when it is pressed must suffer greater resistance, when 

 it slides in the direction of the point, than in that of 

 the root ; and to obviate the inconvenience which this 

 would occasion in spinning, wool is Covered with some 

 unctuous matter, which in some measure smooths its 

 asperities, and thus facilitates that operation. After 

 the wool is manufactured, the oil being no longer use- 

 ful, is removed both for the sake of cleanliness, and to 

 enable the stuff to absorb more effectually the dye. The 

 cloth is therefore taken to the fulling mill, where it is 

 beaten with large beettlcs, in a trough of water, con- 

 taining diffused through it a quantity of fullers earth. 

 The earthy matter uniting with the oil, forms a kind of 

 soap, which is carried off by the constant action of the 

 machinery, and the effusion of fresh portions of w ater. 

 See WOOL. 



CHAP. III. Of Silk. 



External '^ Silk is of animal origin, and consists of the fine 

 characters, threads with which the liumbi/i mori, a moth belonging 

 to l.innaeus's third order of insects, envelopes itself be- 

 fore it emerges in the perfect state. Silk is naturally 

 covered with a gummy or glutinous substance, to which 

 it owes its stiffness and elasticity ; it is al--o frequently 

 tinged with a yellowish colouring matter. The pur- 

 poses for which silk i- usually employed, require that 

 it should IK- freed from both these, matters ; and thi- is 

 commonly done by means of soap. Besides the gum- 

 my and colouring matters, there is also, according to 

 Hoard, a substance to be removed, which has a con- 

 siderable resemblance to wax. He states, that tile gum- 

 my matter, which is soluble in water, usually amounts 

 to about 24 per cent, and the colouring matter to about 



l-55th, or 1-GOth part of the silk ; the wax seldom ex- Of Stufli. 

 ceeds the l-100th part of the silk, and is frequently **~" V"^ 

 less than half that quantity. All these substances are 

 removed by scouring with soap; but this operation must 

 be slightly modified, according to the purposes for which 

 the silk is intended : it ought not to be so complete for 

 silks which are to be dyed, as for those which are to be 

 white, and a difference ought to be observed in the for- 

 mer case, according to the colour to be given. For 

 common colours, it is generally thought sufficient to 

 boil the silk for three or four hours, in a solution of 

 twenty pounds of soap for each hundred of silk, tak- 

 ing care to fill up the kettle from time to time, to re- 

 place the water carried off by evaporation. The quan- 

 tity of soap is increased for those silks which are to be 

 dyed blue ; and still more for those which are to be 

 scarlet, cherry-colour, &c. these colours requiring a 

 brighter ground for their display than such as are of a 

 more delicate hue. 



190. Silk wlu'ch is to remain white commonly under- 

 goes three operations. In the first of these, which is in- 

 tended to remove the gummy matter, it is kept in a silk. 

 solution of thirty pounds of soap to a hundred of silk, 

 the solution being very hot, but not boiling. When it 

 lias been immersed a sufficient length of time for the 

 removal of the gum, which is known by the whiteness 

 it acquires, it is taken out and wrung. In the second 

 operation, the silk is put into bags of cloth, and boiled 

 in a weaker solution of soap for about an hour and a 

 half, taking care to keep the bags constantly stirred, to 

 prevent those which touch the bottom receiving too 

 much heat. The third operation is intended to soften 

 the white, and render it more pleasing, by giving it a 

 slight shade of some delicate colour. For this purpose, 

 a solution of silk is employed, the proper strength of 

 which is determined by its mode of frothing; this is 

 slightly tinged with a colour of the shade to be given, 

 and the silk is then moved about in it until it acquires 

 the desired hue. At Lyons, where silk is scoured of a 

 beautiful white, no soap is used in the third operation ; 

 but after the second, the silks are washed, fumigated 

 with sulphur, and azured with river water. 



191- Hoard thinks, that instead of employing the Hoard's 

 soap at different times, it is more advantageous to em- 

 ploy the whole quantity to be used at once, and by 

 that means shorten the boiling to an hour, or a little 

 more ; the silk is thus left with more of its natural soft- 

 ness and lustre, as well as stronger and more elastic. 

 He recommends, indeed, that when it is to be dyed of 

 a crimson, or any other colour which would not be af- 

 fected by the yellowish tinge of the silk in its raw 

 state, the latter ought not to be completely removed; 

 because, when this is done, the dyed colour pos~i 

 less brilliancy than it would otherwise have. 



19'J. As soap seems to impair the lustre of silk, the j 

 Academy of Sciences, in 17<>1, proposed, as the sub- method." 

 ject of a prize dissertation, to find a method of scour- 

 ing it without soap ; and the prize was adjudged to M. 

 Kig.md of St Quentin, who proposed substituting for 

 soap a solution of soda, or carbonate of soda, so much 

 diluted as not to affect the texture of the silk. But 

 same inconvenience must have attended the practice of 

 this method, as it is not adopted, though generally 

 known, and easy of execution. Hoard, indeecl, affirms, 

 that the gummy matter of the silk is less effectually re- 

 moved by soda than by soap. 



iy3. The Abbe Collomb has given an account of a collomb'i 

 method of scouring silk by the action of water alone, method. 

 which deserves attention. Having boiled silk for about 



