358 BLACK DYE 



The process for dyeing merinos black is, for 100 ll>s. of them to put 10 Ibs. of cop- 

 peras into tho bath of pure "water, and to work therein for a quarter of an hour, as 

 soon as it is tepid, one-third of the goods ; then to replace that portion by tho second, 

 and after another quarter of an hour, to put in the last third. Each portion is to be 

 laid aside to air in the cold. The bath being next heated to 140 F., the merinos 

 are to be treated as above piecemeal ; but tho third time it is to be passed through 

 the bath at a boiling heat. Being now well mordanted, tho goods are laid aside to air 

 till the following day. The copper being charged with water, 60 Ibs. of ground log- 

 wood, and 2 Ibs. of argol, and heated, the goods are to be passed through, while boiling, 

 for half an hour. They are then rinsed. 



Different operations may bo distinguished in dyeing silk black : the boiling of tho 

 silk, its galling, the preparation of the bath, the operation of dyeing, the 

 softening of the black. 



Silk naturally contains a gummy substance, which gives it the stiffness and elas- 

 ticity peculiar to it in its native state ; but this adds nothing to the strength of the 

 silk, which is then styled raw ; it rather renders it, indeed, more apt to wear out by 

 the stiffness which it communicates ; and although raw silk more readily takes a black 

 colour, yet the black is not so perfect in intensity, nor does it so well resist the 

 reagents capable of dissolving tho colouring particles, as silk which is scoured or 

 deprived of its gum. 



To cleanse silk intended for black, it is usually boiled four or five hours with one- 

 fifth of its weight of white soap, after which it is carefully beetled and washed. 



For the galling, nut-galls equal nearly to three-fourths of the weight of the silk 

 are boiled during three or four hours ; but on account of the price of Aleppo galls, 

 more or less of tho white gall-nuts, or of even an inferior kind called galon, berry or 

 apple galls, are used. The proportion commonly employed at Paris is two parts of 

 Aleppo galls to from eight to ten parts of galon. After the boiling, the galls are 

 allowed to settle for about two hours. The silk is then plunged into the bath, and 

 left in it from twelve to thirty-six hours, after which it is taken out and washed in 

 the river. 



Silk is capable of combining with quantities, more or less considerable, of the astrin- 

 gent principle ; whence results a considerable increase of weight, not only from the 

 weight of the astringent principle, but also from that of the colouring particles, which 

 subsequently fix themselves in proportion to the quantity of tho astringent principle 

 which had entered into combination. Consequently, the processes are varied accord- 

 ing to the degree of weight which it is wished to communicate to the silk ; a circum- 

 stance requiring some illustration. 



The commerce of silk goods is carried on in two ways : they are sold either by 

 the weight, or by the surface, that is, by measure. Thus the trade of Tours was 

 formerly distinguished from that of Lyons ; the silks of the former being sold by 

 weight, those of the latter by measure. It was therefore their interest to surcharge 

 the weight at Tours, and, on the contrary, to be sparing of the dyeing ingredients at 

 Lyons ; whence came the distinction of light black and heavy black. At present, 

 both methods of dyeing are practised at Lyons, the two modes of sale having been 

 adopted there. 



Silk loses nearly a ftnirth of its weight by a thorough boiling, and it resumes, in the 

 light black dye, one-half of this loss ; but in the heavy black dye, it takes sometimes 

 upwards of a fifth more than its primitive weight a surcharge injurious to the beauty 

 of the black and the durability of the stuff. The surcharged kind is denominated 

 English black, because it is pretended that it was practised in England. Since silk 

 dyed with a great surcharge has not a beautiful black, it is usually destined for weft, 

 and is blended with a warp dyed of a fine black. 



The peculiarity of the process for obtaining tho heavy black consists in leaving the 

 silk longer in the gall-liquor, in repeating the galling, in passing the silk a greater 

 number of times through the dye, and even letting it lie in it for some time. The first 

 galling is usually made with galls which have served for a preceding operation, and 

 fresh gall-nuts are employed for the second. But these methods would not be suffi- 

 cient for giving a great surcharge, such as is found in what is called the English 

 black. To give it this weight, the silk is galled without being ungummed ; and, on 

 coming out of the galls, it is rendered supple by being worked on the jack and pin. 



The silk dyers keep a black vat, and its very complex composition varies in different 

 dye-houses. These vats are commonly established for many years ; and when their 

 black dye is exhausted it is renovated by what is called in France a brevet. When 

 the deposit which has accumulated in it is too great, it is taken out, so that at the end 

 of a certain time nothing remains of the several ingredients which composed the 

 primitive bath, but which are not employed in the brevet. 



For tho dyeing of raw silk black, it is ' galled ' cold, with the bath of galls 



