DYEING. 



271 



Professes 

 uj' Dyeing. 



quer acknowledges, that many of these substances are 



Dyeing pro- 

 cess. 



Softening. 



M. AngKY 

 MM 



and, indeed, few of them are now employed. 

 Iron filings are generally added to the dye-lwth ; but 

 some dyers in France use in its stead the powder found 

 hi the troughs of cutlers' grindstones. 



424. The bath for dyeing silkought never to be allow- 

 ed to boil. Gum and solution of iron are added to it, 

 in different proportions, according to the various pro- 

 cesses ; and when it is observed that the gum is dissol- 

 ved, and the liquor nearly boiling, it is allowed to set- 

 tle for about an hour. The silk, being dipped in the 

 bath, and managed in the usual way, is taken out when 

 it has absorbed a sufficiency of the "dye, wrung, and ex- 

 posed to the action of the air, which deepens the black. 

 After it has had three wringings, the bath is heated 

 anew, fresh portions of gum and sulphate of iron being 

 added as at first : the operation performed in the interval 

 between two heatings is, in France, called a fire (un fen). 

 The light black receives two fires, but the heavy requires 

 tliree; and the silk is also allowed to remain in the bath 

 for twelve hours after the last fire. When the dyeing 

 is finished, the silk is rinsed in a vessel with cold water, 

 by turning or shaking it. 



425. When silk is taken out of the black dye, it is 

 extremely harsh ; and to free it from this quality, it 

 must undergo an operation called softening. For this 

 purpose, a solution of 4 or 5 pounds of soap for every 

 hundred pounds of silk, is poured through a cloth into 

 a large vessel of water: being well mixed, the silk is 

 put in, and left about a quarter of an hour, when it is 

 wrung and dried. 



420'. The quantity of galls necessary for dyeing silk 

 black, renders the process very expensive ; and it is 

 therefore an object of considerable importance, to find 

 some method of diminishing their quantity. The follow- 

 ing process has, for this purpose, !>een recommended by 

 M. Aii'.-li'-, who was a comi>etitor for tiie pri/e propo- 

 sed in 1771), by the Academy of Lyons, of which this 

 was the object. 



427. Silk carefully boiled and washed in the river, is 

 to be immersed in a strong decoction of green walnut 

 peels, and left in it till the colour of the Iwith is exhaust- 

 ed. It is then taken out, slightly wrung with the pin, 

 dried, and washed in the river. The decoction of wal- 

 nut peels is made by boiling a full quarter of an hour, 

 when it U taken from the fire, and allowed to subside 

 before dipping the silk, which has been previously im- 

 mersed in warm water. A blue ground is next given, 

 by means of logwood and verdigrise. For every pound 

 of silk, an ounce of verdigris i* dissolved in cold wa- 

 ter; the silk is left in this solution two hours ; it is then 

 dipped in a strong decoction of logwood, wrung out 

 slightly, and dried Ix-fore it is washed at the river. For 

 li','ht blacks, galling may be altogether omitted ; but to 

 obtain a heavy black, half a pound of galls may be lined 

 tor every pound of silk. To prepare the bath, two 

 pounds of galU and three of sumach, are macerated in 

 twenty-five gallons of water, over a slow fire, for twelve 

 hours. After straining, three pounds of sulphate of 

 /on, and as much gum-arabic, are dissolved in it. In 

 dissolution, the silk in dipped at two different times, 

 leaving it in two hours each time, taking care to air it 

 after the fir.,t dipping, and to dry it before giving it the 

 second fire, when it is to be again aired and dried. It 

 19 then beetled twice at the river; after which a third 

 fire is given it in the same manner as Ijefore, except tlnit 

 it is left in the bath four or five hours. When drained 

 and dried, it is a|irain beetled twice at the river. Care 

 must be taken that the heat during the operation do not 

 5 



exceed 122 of Fahrenheit's thermometer ; and before 

 the last two fires, half a pound of sulphate of iron, and 

 as much gum-arabic, must be added. For removing 

 the harshness of the black dye, M. Angles prefers the 

 decoction of weld to the solution of soap. 



423. M. Angles asserts, that if silk be dyed blue 

 with indigo, previous to its being dipped for black, 

 it will take only a mealy colour ; but that a velvety 

 Wack will be obtained if it be prepared with logwood 

 and verdigrise. He says also that green walnut peels 

 soften the silk. Though a fine black may be procured 

 from green walnut peels, and the bath above described, 

 he notwithstanding adds logwood and verdigrise, that 

 he may not be obliged to use a large quantity of sul- 

 phate of iron, which weakens the silk. Lastly, he 

 thinks that galls serve only to give the silk weight, and 

 that sumach is sufficient for the dye. 



429. The Chinese are said to improve their black dye Blati, how 

 upon silk, by passing it, when dyed, through a bath improved 

 containing one pound of starch, with half as much of ?. th 

 the oil of linseed, or of rape or hempseed, for every five nese " 

 or six quarts of water. A great variety of shades are 

 obtained by the mixture of Brazil-wood, logwood, ar- 

 chil, and galls, and by a browning with sulphate of 

 iron ; but all these shades, though they have a pleasing 

 lustre, are apt to fade. It is rather by the eye, than by 

 any particidar rules, tliat the dyer is to be guided in 

 communicating them. 



III. Processes for Dyeing Cotton and Linen, Black, %c. 



4JO. In order to dye cotton and linen black, a solu- Black vat. 

 tion of iron is employed, which, in France, receives the 

 name of the black vat. The solution, which is a kind 

 of acetate of iron, resembling a preparation of that me- 

 tal, described under the head of Mordants (9 k), is form- 

 ed with vinegar or small beer, or small wine made from 

 grapes, after they have been pressed, by adding water 

 to them ; rye meal, or some other ingredient being add- 

 ed, to assist the acetification. Pieces of old iron are 

 thrown into this liquor, which is allowed to stand till 

 wanted, but never used in less than six weeks, or two 

 months. To this bath astringents are frequently add- 

 ed, particularly the decoction of alder bark, which of 

 it -elf has the property of dissolving a considerable por- 

 tion of oxide of iron. 



431. The following method of dyeing cotton and li- Process fe!- 

 nen, as practised at Itouen, is given by M. le Pileur lowed at 

 d'Apligny. They are first dyed sky-blue in the vat, Rouen - 

 then wrung out, and dried. They are next galled, 

 using four ounces of galls to every pound of stuff, and 

 leaving it twenty-four hours in the gall liquor, after 

 which they are again wrung out and dried. About five 

 quarts of the liquor of the black vat for every pound 

 are then poured into a tub, in which the thread is work- 

 ed with the hand, pound by pound, about a quarter of 

 an hour, when it is wrung out, and aired. This ope- 

 ration is twice repeated, adding each time a fresh sup- 

 ply f the black vat, which ought to be carefully scum- 

 med. It is then taken out, aired, wrung, washed at 

 the river to cleanse it effectually, and dried. When 

 this stuff is to be dyed, a pound of alder bark for every 

 pound of the stuff is boiled for an hour in a sufficient 

 quantity of water. About half the bath that served for 

 the galling, and half as much sumach as alder bark is \ 



then added, and the whole boiled together for two 

 hours, and then strained through a sieve. When the 

 liquor is cold, the stuff is put in and carefully worked, 

 airing it from tinoe to time: it is then let down into tli- 



