BLACK DYE 357 



phates give a reddish black ; the hydrochloric and nitric acid salts yield a black with 

 a blue lustro. 4. Equal volumes of bi-sulphato and bi-hydrochloride of aniline give 

 excellent results. 5. The bi-chromato of potash solution must be concentrated, con- 

 taining not less than 80 grammes of salt to the litre. 



' A dark green is first produced on passing the cloth into a hot-soap bath. After 

 washing it thoroughly this passes into pure black. 



' By printing the cloth "with fatty matters or resins, previous to the application of 

 the dyeing solutions, white patterns on a black ground can be obtained.' 



The following processes for dyeing woollen stuff will be found to produce excellent 

 results. For 1 cwt. of cloth previously dyed blue : There is put into a boiler of 

 middle size, 18 Ibs. of logwood, with the same quantity of Aleppo galls, the whole 

 being enclosed in a bag ; this is boiled in a sufficient quantity of water for 12 hours : 

 one-third of this decoction is transferred into another boiler with 2 pounds of verdi- 

 gris ; and the stuff is passed through this solution, stirring it continually during two 

 hours, taking care to keep the bath very hot without boiling. The stuff is then lifted 

 out, another third of the bath is added to the boiler, along with 8 pounds of sulphate 

 of iron or green vitriol. The fire is to be lowered while the sulphate dissolves, and 

 the bath is allowed to cool for half an hour, after which the stuff is introduced, and 

 well moved about for an hour, and then it is taken out to air. Lastly, the remain- 

 ing third of the bath is added to the other two, taking care to squeeze the bag well. 

 18 or 22 Ibs. of sumach are thrown in ; the whole is just brought to a boil, and 

 then refreshed with a little cold water ; 2 pounds more of sulphate of iron are added, 

 after which the stuff is turned through for an hour. It is next washed, aired, and 

 put again into the bath, stirring it continually for an hour. After this, it is carried to 

 the river, washed well, and then fulled. Whenever the water runs off clear, a 

 bath is prepared with weld, which is made to boil for an instant ; and after refresh- 

 ing the bath, the stuff is turned in to soften, and to render the black more fast. 

 In this manner a very beautiful black is obtained, without rendering the cloth too 

 harsh. 



Commonly, more simple processes are employed. Thus the blue cloth is simply 

 turned through a bath of gall-nuts, where it is boiled for two hours. It is next passed 

 through a bath of logwood and sulphate of iron for two hours, without boiling, after 

 which it is washed and fulled. But in all cases the cloth, after passing through the 

 blue vat, should be thoroughly washed, because the least remains of its alkalinity 

 would injure the tone to be given in the black copper. 



Hellot found that the dyeing might be performed in the following manner : For 

 20 yards of dark blue cloth a bath is made of 2 Ibs. of fustic (Madura tinctoria), 4^ Ibs. 

 of logwood, and 11 Ibs. sumach. After boiling the cloth in it for three hours it is 

 lifted out, 1 1 Ibs. of sulphate of iron are thrown into the boiler, and the cloth is then 

 passed through it during two hours. It is now aired, and put again in the bath for 

 an hour. It is, lastly, washed and scoured. The black is less velvety than that by 

 the preceding process. Experience convinced him that the maddering prescribed in 

 the ancient regulations only gives a reddish cast to the black, which is obtained finer 

 and more velvety without madder. 



According to Lewis, the proportions which the English dyers most generally adopt 

 are, for 112 Ibs. of woollen cloth, previously dyed of a dark blue, about 5 Ibs. of sul- 

 phate of iron, as much gall-nuts, and 30 Ibs. of logwood. They begin by galling the 

 cloth ; they then pass it through the decoction of logwood to which the sulphate of 

 iron has been added. 



When the cloth is completely dyed, it is washed in the river, and passed through the 

 fulling-mill till the water runs off clear and colourless. Some persons recommend, for 

 fine cloths, to full them with soap- water. This operation requires an expert workman, 

 who can free the cloth thoroughly from the soap. Several recommend, at its coming 

 from the fulling, to pass the cloth through a bath of weld, with the view of giving soft- 

 ness and solidity to the black. Lewis says, that passing the cloth through weld, after 

 it has been treated with soap, is absolutely useless, although it may be beneficial when 

 this operation has been neglected. 



The following German process is cheap and good.. 100 Ibs. of cloth or wool are 

 put into the copper with sufficient water and 15 Ibs. of Salzburg vitriol (potash-sul- 

 phate of iron) and 5 Ibs. of argol, heating the bath gradually to boiling, while the 

 goods are well worked about for two hours, taking them out, and laying them in a 

 cool place for twenty-four hours. They are then to be put in a lukewarm bath of 

 from 25 to 30 Ibs. of logwood, and 10 Ibs. of fustic, and to be worked therein while 

 it is made to boil during two hours. The goods are now removed, and thero is put 

 into the copper \\ Ibs. of verdigris dissolved in vinegar ; the goods are restored into 

 the improved bath, and turned in it for half an hour, after which they are rinsed and 

 dried. 



