DYEING. 



boiled in twelve or fifteen quarts of wa- 

 ter till wholly dissolved ; the vessel that 

 contains this liquor is to be half filled 

 with old iron made red hot, and the whole 

 to be exposed to the air and light for . a 

 week ; an equal quantity of red-hot iron 

 is to be thrown into as many quarts of 

 vinegar, which is also to be exposed to 

 the air and light : after some days, the 

 two solutions are to be mixed together, 

 and exposed to the air and light for ano- 

 ther week. The liquor is then to be 

 decanted, and kept in a close vessel for 

 use. 



The linen or cotton left in this liquor 

 for twenty-four hours acquires a good 

 black. If the liquor does not contain 

 iron enough, a fresh portion should be 

 used, which will produce a permanent 

 black. This liquor may be advantage- 

 ously substituted for sulphate of iron in 

 dyeing wool or silk, which only require 

 to be dipped in a decoction of logwood, 

 after being taken out of the bath, to give 

 them a beautiful black. 



Berthollet mentions, that iron ought to 

 be more oxygenated to unite with cotton 

 or linen, than with wool or silk ; and that 

 therefore the longer the iron liquor is ex- 

 posed to the air the better. The place of 

 galls, which bear an high price, is fre- 

 quently supplied by oak-bark, oak saw- 

 dust, sumach, the cups and husks of 

 acorns, and other astringents. 



Of dyeing Wool blue. 



Blue may be dyed by woad alone, 

 which would give a permanent but not 

 a deep blue ; but if indigo be mixed 

 with it, a very rich colour will be ob- 

 tained. 



The following is the method of pre- 

 paring a blue vat, recommended by M. 

 Quatremere. Into a vat about seven and 

 a half feet deep, and five and a half broad, 

 are thrown two balls of woad, weighing 

 together, about four hundred pounds, first 

 breaking them; thirty pounds of weld 

 are boiled in a copper for three hours, in 

 a sufficient quantity of water to fill the 

 vat ; when this decoction is made, twenty 

 pounds of madder, and a basket full of 

 bran, are added, and it is boiled half an 

 hour longer. This bath is cooled with 

 twenty buckets of water ; and after it is 

 settled the weld is taken out, and it is 

 poured into the vat ; all the time it is 

 running in, and for a quarter of an hour 

 after, it is to be stirred with the rake. 

 The vat is then covered up very hot, 

 and left to stand for six hours, when it 



is raked again for half an hour, and 

 this operation is repeated every three 

 hours. 



When blue veins appear on the surface 

 of the vat, eight or nine pounds of quick 

 lime are thrown in. Immediately after 

 the lime, or along with it, the indigo is 

 put into the vat, being first ground fine 

 in a mill with the least possible quantity 

 of water. When it is diluted to the con- 

 sistence of a thick pap, it is drawn off 

 at the lower part of the mill, and thrown 

 thus into the vat. The quantity of indigo 

 depends on the shade of colour required. 

 From ten to thirty pounds may be put to 

 the vat now described. 



If on striking the vat with the rake a 

 fine blue scum arises it is fit for use, after 

 being stirred twice with the rake in six 

 hours, to mix the ingredients. Great 

 care should be taken not to expose the 

 vat to the air, except when stirring it. 

 As soon as that operation is over, the vat 

 is covered with a wooden lid, on which 

 are spread thick cloths, to retain the heat 

 as much as possible. Notwithstanding 

 this care, the heat is so much diminished 

 at the end of eight or ten days, that 

 the liquor must be re-heated, by pouring 

 the greater part of it into a copper over 

 a large fire : when it is hot enough it is 

 returned into the vat, and covered as be- 

 fore. 



.This vat is liable to two inconveniences; 

 first, it runs sometimes into the putrefac- 

 tive fermentation, which is known by the 

 fetid odour it exhales, and by the reddish 

 colour it assumes. This accident is re- 

 medied by adding more lime. The vat 

 is then raked, after two hours lime is put 

 in, the raking performed again, and these 

 operations are repeated till the vat is re- 

 covered ; secondly, if too much lime is 

 added, the necessary fermentation is re- 

 tarded ; this is remedied by putting in 

 more bran or madder, or a basket or two 

 of fresh woad. 



When cloth is to be dyed, the vat is 

 raked two hours before the operation, and 

 to prevent it from coming in contact with 

 the sediment, which would cause inequa- 

 lities in the colour, a kind of lattice of 

 large cords, called a cross, is introduced ; 

 when wool is to be dyed, a net with small 

 meshes is placed over this. The wool or 

 cloth being thoroughly wetted with clear 

 water, a little warm, is pressed out, and 

 dipped into the vat, where it is moved 

 about a longer or a shorter time, accord- 

 ing as the colour is intended to be more 

 or Jess deep, taking it out occasionally to 

 expose it to the air j the action of which 



