DYEING. 



259 







of Dyeing. 



Preparation 

 ef the silk. 



Weld bath. 



Golden and 



jonquille 



yellows. 



Straw co- 



Quercitron 



i to 

 lk every 

 lof 



Lively yel- 

 low- 



II. Processes for Dyeing Silk Yellow. 



325. Before the introduction of quercitron bark, 

 weld was almost the only colouring matter employed 

 for dyeing silk of a plain yellow. The silk to be dy- 

 ed ought to be previously scoured with soap, in the 

 proportion of twenty pounds of soap to the hundred of 

 stuff, and afterwards alumed, and refreshed or washed 

 after the alumina. 



326. The bath is prepared with two pounds of weld 

 for each pound of silk, and after boiling a quarter of an 

 hour, is passed through a sieve or cloth into a vat. 

 When the temperature is such as the hand can bear, the 

 silk is put in, and turned until the colour is become 

 uniform. In the meantime, the weld is exposed to a 

 second boiling in fresh water ; and half the first bath 

 being removed, its place is supplied by a fresh decoction. 

 This bath may be used a little hotter than the first, 

 but care must be taken not to allow it to be so warm as 

 to dissolve any part of the colour already fixed. The 

 silk is turned as before ; and in the meantime, a quan- 

 tity of soda is to be dissolved in a part of the second 

 decoction. After being turned a few minutes, a hank 

 is wrung with the pin, to ascertain if the colour is suf- 

 ficiently full, and has the proper golden cast ; if not, 

 a little more of the alkaline solution is added, until the 

 silk attains the desired shade. 



327. When we wish to produce yellows, with more 

 of a gold or jonquille colour, a quantity of annotta, 

 proportioned to the shade required, is added to the 

 weld bath, along with the alkali. If the lighter shades 

 are to be given, such as pale lemon, or canary-bird co- 

 lour, the silk must be previously well scoured, as the 

 beauty will depend greatly upon the whiteness of the 

 ground to v.'hich they are applied. The strength of 

 the bath is regulated by the shade required ; and if it 

 be intended that the colour should have a greenish 

 tinge, a little indigo is added to the bath ; but this will 

 be unnecessary if the silk has been previously azured. 

 For these lighter shades, a smaller proportion of alum 

 should be used. 



328. Scheffer directs, that the silk should be soaked 

 twenty-four hours in a solution of tin, made with four 

 parts of nitric acid, one of common salt, and one of 

 tin, and saturated with tartar ; that it should be wash- 

 ed, and then boiled half an hour with an equal quan- 

 tity of weld flowers. He says, that a fine straw co- 

 lour is thus obtained, which jxwsesses the advantage of 

 resisting the action of acids. By following this pro- 

 cess, says Berthollet, very little "ti'i should !>, left in 

 tin 1 Milution, because the acid of tartar precipitates it 



All the different shades of yi !].>," says Dr 

 Bancroft, " commonly dyed upon silk from weld, may 

 be obtained with equal facility and beauty, and more 

 cheaply, by employing the bark (quercitron) in its stead, 

 after the rate of from one or two pounds for every twelve 

 pounds of silk, according to the particular shade of colour 

 wanted. For this purpose, the bark, ]N>wdercd and 

 tied up in a bag, should be put into the dyeing vessel 

 whilst the water is cold ; and as soon as it becomes a 

 little more than blood warm, the silk, previously alum- 

 ed, should also be put in and dyed as usual ; and when 

 the higher yellows are wanted, a little chalk or pearl 

 ashes may be added towards the end of the operation 

 as mentioned for the dyeing of wool. 



330. " Where shades of yellow, more lively than 

 any which can be given, either by weld or bark, with 

 the aluminous basis only, are wanted, it will be advan- 

 tageous to employ a little of the murio-sulphate of tin 



Processes 



and but a little of it, because the calx of tin, unless 



sparingly used, always diminishes the glossiness of ^yem^ 



silk. To produce the shades in question, it will be 



sufficient to boil, after the rate of four pounds of bark, 



with three pounds of alum, and two pounds of murio- 



sulphate of tin, in a suitable quantity of water, for ten 



or fifteen minutes ; and the heat of the liquor being af- 



terwards reduced, so that the hand can bear it, the silk 



is to be put in and dyed as usual, until it has acquired 



the proper shade, (which it will do speedily,) taking 



care, however, to agitate the liquor constantly, that 



the colouring matter, which would otherwise subside 



in a considerable degree, may be kept equally disper- 



sed through the liquor." See Phil, of Perm. Col. vol. 



ii. p. 146. 



331. An aurora colour may be communicated tc silk Aurora *- 

 by annotta. The silk to be dyed is previously well lour> 

 scoured, with twenty pounds of soap to the huntlred of 



stuff, and then immersed in a bath of water, to which 

 more or less of the alkaline solution of annotta has been 

 added, according to the shade required. The heat of 

 the bath ought to be between that of tepid and boiling 

 water. After the silk has acquired a uniform colour, 

 one of the hanks must be taken out, washed, and wrung, 

 to ascertain the state of the colour ; if it is not suffi- 

 ciently deep, more solution of annotta must be added, 

 and the silk again turned. When the desired shade has 

 been obtained, die silk is well washed, and beetled 

 twice by a stream of water, to free it from the super- 

 fluous colouring matter, which would only injure the 

 beauty of the colour. The colour thus communicated 

 may be rendered orange, by reddening the silks with 

 vinegar, alum, or lemon juice. The acid saturates the 

 alkali employed in dissolving the colouring matter of 

 annotta, and destroys the yellow shade which the al- 

 kali had imparted, while it restores the natural colour 

 of the annotta, which inclines a good deal to red. 



332. A yellow of great brightness, but little durabi- Y UOW .'>BI 

 ,.. rp turmeric. 

 hty, may IK- dyed upon silk by turmeric. 1 wo pro- 



cesses are recommended by Guhliche, which appear 

 to be in substance the same. The first consists in alum- 

 ing in the cold for twelve hours, a pound of silk in a 

 Milution of two ounces of alum, and dyeing it hot, but 

 without boiling, in a bath composed of two ounces of 

 turmeric, and a quart of aceto-citric acid, mixed with 

 three quarts of water ; by the second process, the co- 

 louring matter of the turmeric is extracted by aceto-ci- 

 tric acid, and the silk alumed, is dyed, either cold, or 

 only moderately warm. 



III. Processes for Dyeing Cotton and Linen Yellorv. 



333. Cotton is prepared for the yellow dye by pre- Preparation 

 viou>ly scouring it with a ley composed of the ashes of of the stuffs. 

 green wood'; it is then washed, dried, and alumed with 

 one-fourth of its weight of alum ; after twenty-four 



hours it is taken out of the aluming and dried without 

 being washed. A weld bath is then prepared, in the Weld bat "- 

 proportion of a pound and a quarter of weld for each 

 pound of cotton, into which the cotton is immersed and 

 wrought in it till it sacquires the proper shade. It is 

 then taken out, and soaked for an hour and a half in a 

 solution of sulphate of copper or blue vitriol, in the 

 proportion of one-fourth the weight of the cotton. 

 Lastly, it is thrown, without being washed, into a boil. 

 ing solution of white soap made with the same pro- 

 portions ; and after being duly stirred and boiled in it 

 for nearly an hour, it is well washed and dried. 



334. When a deeper yellow is required, the cotton Deep yel- 

 is not alumed, but two pounds and a half of weld are low> 



