Of the Processes for dyeing black, ' According to the method described by Hellot, woollen cloth to be dyed black ought to have received the deepest blue tint, to have been washed in the river as soon as taken out of the vat, and t to have afterwards been cleaned at the fulling mill.
For an hundred pounds of the stuff, ten pounds of logwood, and ten pounds of Aleppo galls powdered, are put into a bag, and boiled for twelve hours in a mid dle sized copper, with a sufficient quan tity of water. One-third of this bath is put into another copper, with two pounds of verdigrise, and into this the stuff is im mersed, stirring it continually for two hours, and observing to keep the bath very hot, without letting it boil. The stuff ,is then taken out, and a portion of the bath equal to the former is put into the copper, with eight poUnds of vitriol, or sulphate of iron. The fire is now to be diminished, and the bath suffered to cool fbr half an hour, whilst the vitriol 'dis solves ; the stuff is then put in again, moved about well for an hour, and after wards taken out to air. Lastly, the re mainder of the bath is added, taking care that the bag be well pressed out. Fif teen or twenty pounds of sumach are now put in, and the bath is made to boil once, and then immediately stopped with a little cold water ; two pounds more of n the sulphate of iron are added, and the stuff is kept another hour. The stuff is now washed, aired, and again put into the copper, constantly stirring it for an hour : it is then carried to the river, well washed, and then fulled When the wa ter comes' off clear, another bath is pre -pared with weld, which is made to boil for a moment, and after being cooled, the stuff is passed through it, to soften it, and render the black more firm. In this manner a very' beautiful black is ' obtained, without making the stuff too harsh.
In general, more simple processes are 'employed. • Cloth previously dyed blue is merely boiled in a bath of galls for two hours ; it is then kept two •hours in the bath of logwood and sulphate of iron, without boiling, and afterwards washed and fulled. Ni. Hellot has also found the following method to succeed. For fif teen ells of deep blue cloth, a bath is to be made with a pound and a half of yel low wood, five pounds of !ogwood, and ten pounds of sumach. After having
boiled the cloth in this bath for three hours, it is taken out, ten pounds of sul phate of iron are put into the copper, and the cloth is then put into it for two hours more. It is then aired, put into I he bath again for another hour, and after wards washed and fulled. This black is less velvety than that of the process first described.
Black may be dyed without a blue ground, and this is usually done for stuffs of low price. In this method the stuff is dyed of a brown, or root colour, with green walnut peels, or the root of the walnut tree : they are then blackened as above directed.
The proportions used by the English dyers are, for every hundred pounds' of woollen cloth, dyed first of a deep blue, about five pounds of sulphate of iron, five pounds of galls, and thirty of logwood. They begin with galling the cloth, and then pass it through the decoction of log wood, to which the sulphate of iron has been added.
Some recommend fine cloths to be full ed with soap suds; but this operation re quires an experienced workman, to cleanse the cloth perfectly of the soap. Many advise to give the cloth a dip in a bath of weld when it comes from the full ing mill, which they say softens it, and fixes the black. Lewis says, the weld bath is totally useless when the cloth has been treated with soap-suds, though in other cases it may be of advantage. He ascribes its effects entirely to the alkali with which the dyers commonly prepare its decoction.
The leaves of the uva ursi may be em ployed instead of galls. They must be carefidly dried in autumn, so that they may remain green. When they are to be used, 100 pounds of wool are boiled for two hours with sixteen pounds of sul phate of iron and eight of tartar : the day fbllowing the cloth is to be rinsed as af ter aiming: 150 pounds of uva ursinare then to be boiled in water for two hours, and after their being taken out, a hide madder is to be added to the liquor, at the same time putting in the cloth, which is to remain there an hour and a half, or an hour and three quarters, after which it is to be rinsed in water. This process gives a pretty good black to blue cloth, but only a deep brown to white : the madder and tartar are supposed by Lewis to be useless.