DYEING. 



263 



)yeing pro- 



rurkcy 



Process** the bath has undergone its usual course, it is refreshed 

 ji' Dyeing, with about two pounds of potash, and three or four 

 ~"^~~" ounces of madder; it is then raked ; and in four hours 

 is fit for dyeing. 



360. Before being immersed in the bath, the silk is 

 boiled with soap, in the proportion of thirty pounds of 

 the latter for every hundred pounds of the former ; 

 and afterwards well cleansed from it by two or more 

 beetlings at the river. As silk is apt to take the dye 

 unequally, it is necessary to dye it in small portions, 

 one hank being dipped at a time, by applying it to a 

 wooden cylinder, and turning it once or oftener in the 

 bath. It is then well wrung and aired, to change the 

 green colour to a blue. When it has assumed the pro- 

 per shade of colour, it is thrown into clear water, and 

 then wrung repeatedly with the pin. Lastly, it is 

 dried as speedily as possible. In winter, and in damp 

 weather, it should be dried in a chamber heated by a 

 stove, and hung upon a frame kept constantly in mo- 

 tion. 



361. When it is required to give silk a deep blue, 

 <tue- indigo alone is insufficient for the purpose : it must 



first receive a ground from some other colouring mat- 

 ter. For the Turkey blue, which is the deepest, the 

 silk must be prepared in a strong bath of archil ; and, 

 loyal blue. fo r the Royal blue, one of the same kind, but weaker. 

 A blue, equal in deepness to the royal blue, may be 

 given by employing cochineal instead of archil. 



362. A blue of little durability is communicated to 

 silk by means of verdigrise and logwood. Berthollet 

 says, that this dye might be rendered more lasting, by 

 first giving it a lighter shade than is intended, in a bath 

 of this kind, afterwards dipping it in an archil bath, 

 and, lastly, in the indigo vat. 



363. To dye raw silk blue, that which is naturally 

 white should be chosen. It ought to be thoroughly 

 soaked in water, and afterwards put into the vat in se- 

 parate hanks, as already mentioned with respect to 

 scoured silk. If raw silk is to be dyed of the deeper 

 shades of blue, it must also be treated in the same man- 

 ner. The mode of applying the Prussian blue to silk 

 is the same as the process already described for dyeing 

 it upon wool: in both cases, the dye is very feebly 

 united with the stuff. 



III. Processes for Dyeing Cotton and Linen Blue. 



Indigo vat. 364. The vat for dyeing cotton and linen blue, is, 

 according to Pileur d'Apligny, a cask containing about 

 120 gallons. The quantity of indigo used is generally 

 from six to eight pounds, which, after being pounded, 

 is boiled in a ley, drawn off clear from a quantity of 

 lime equal to the indigo, and double its weight of pot- 

 ash. The boiling is continued till the indigo is tho- 

 roughly penetrated by the ley, carefully stirring it all 

 the while, to prevent the indigo adhering to the bot- 

 tom, and being burnt. 



365. Whilst the indigo is boiling, an equal weight 

 of quicklime is slaked ; about twenty quarts of warm 

 water are added, and in this is dissolved as much green 

 vitriol or sulphate of iron, as is equal to twice the 

 weight of the lime. When the solution is completed, 

 the liquor is to be poured into the vat, which must be 

 previously half filled with water. To this the solution 

 of the indigo must be added, with the remainder of the 

 ley not used in boiling it. When all these are put into 

 the vat, it is filled up to within two or three fingers of 

 the brim, and stirred with the rake two or three times 

 a-day, till it is in a state fit for dyeing, which it will be 



Saw silk, 

 tow dyed. 



Preparation 



f t!,c i .ill. 



in about forty-eight hours!, sometimes sooner, accord- 

 ing to the temperature of the atmosphere. 



366. A simpler process is followed at Rouen, which 

 is thus described by Quatremere. " The vats are con- 

 structed of a kind of flint, covered, within and without, 

 with a coating of fine cement. Every dye-house is 

 furnished with a certain number of these, arranged in 

 parallel lines. Each vat is capable of containing four 

 hogsheads of water, and into it may be put eighteen or 

 twenty pounds of indigo. The indigo having been 

 macerated for a week in a caustic ley sufficiently strong 

 to bear an egg, and then ground in a mill, in which 

 not unfrequently the maceration is made, about three 

 hogsheads and a half of water are put into the vat, and 

 afterwards twenty pounds of lime. When the lime is 

 thoroughly slaked, the vat is raked, and thirty-six 

 pounds of sulphate of iron are put in. When the so- 

 lution is completed, the ground indigo is poured in 

 through a sieve. On that day it is raked seven or 

 eight times ; and, after having stood at rest six-and- 

 thirty hours, it is fit for dyeing. 



367- In dyeing-establishments upon a large scale, 

 vats are set or prepared at different times. The cotton 

 or thread is first dipped in the bath which has been 

 previously most exhausted ; and then carried from vat 

 to vat, till it attains the proper shade. It ought to be 

 wetted before it is put into the first vat, and should not 

 be left in the bath more than five minutes, as, in that 

 time, it imbibes all the colouring matter it can take 

 up. As soon as the dyeing in one vat is finished, the 

 bath should be raked, and not used again till it has 

 stood at least twenty-four hours ; but if it has been 

 freshly prepared, it need not stand so long. 



368. When a vat has been used three or four times, 

 it begins to change ; no more veins appear on the sur- 

 face after raking, or it becomes black. It must then 

 be refreshed ; and, for this purpose, four pounds of 

 sulphate of iron, with two of quicklime, are added, and 

 it is raked twice. A vat may thus be refreshed three 

 or four times, diminishing the ingredients each time, as 

 it declines in strength and quality. 



3(ij). Haussnian describes a bath in which a much 

 smaller proportion of indigo is employed. For three 

 thousand pounds of water, he takes thirty-six pounds 

 of quicklime, which he slakes in two hundred pounds 

 of water : with this he mixes the indigo, well ground : 

 in it dissolves thirty pounds of sulphate of iron in a 

 hundred-and-twenty pounds of hot water ; and, ha- 

 ving left the whole at rest for a quarter of an hour, he 

 finishes the filling of the vat, gently stirring it, with- 

 out intermission. The blue vat, he observes, may be 

 made at discretion, by varying the quantity of indigo. 

 From twelve to twenty pounds may be taken for the 

 quantity of water above directed, or even more, if a 

 colour like that of indigo in substance be required, par- 

 ticularly when it is for dyeing linen. When the vat 

 begins to grow turbid, dyeing in it must be disconti- 

 nued : it must then be stirred, and left till the liquor 

 above the sediment become clear. If the lime ceases 

 to operate, from being saturated with carbonic acid, a 

 fresh portion of it must be added after being slaked in a 

 sufficient quantity of water. If the iron be too much 

 oxidated to act on the indigo, sulphate of iron is to be 

 added, always taking care that there be more lime than, 

 is necessary to saturate the sulphuric acid, the excess 

 being necessary to dissolve the indigo. When the in. 

 digo is exhausted, all that is requisite, is to add a fresh 

 portion ground in water, to stir the vat repeatedly, and 



Processes 

 of Dyeing. 



Process of 

 Quatre- 

 mere. 



Practice in 

 large dye- 

 ing esta- 

 blishment*. 



Refreshing 

 of the vat. 



Process of 

 Haussman. 



