The next morning give the silk four or five wets more, and leave it in the copper all the following night, observing when it is left in, and always when it is worked in, that the heat, must be considerably under the boiling point, and the silk kept covered by the liquor: for if any part be exposed to the air it will be marked.
On dyeing cotton BLACK at Rouen, (from D'Apligny.)
Take one hundred quarts of sour wine, bad vinegar, or small beer; put to either of these twenty-five pounds of old iron hoops rusted by the air or dew; twelve pounds of rye meal or coarse bran; put the whole into a copper and heat it rather more than blood warm. In the summer it would do exposed to the sun and air with a porous cloth over it, to let in the air, but keep out dirt, &c.; the older this solution is the better; but it should be at least two months old.
Cotton skeins are galled by being worked in a solution of galls; alumed and then dyed in weld liquor; this in the result is yellow; they are then passed through a decoction of logwood, and after that of sulphate of iron, a quarter of a pound to every pound of cotton; they are then dyed in madder, half a pound to every pound of cotton.
We cannot recommend this process, although we give it, as much better methods are now known.
To dye cotton BLACK—the London process—used by various calico printers in the suburbs.
Cotton cambric piece-goods are passed through a blotching machine to receive a mordant of acetate of iron, and galled slightly; sumach is used instead when galls are dear; the cotton is then passed through logwood, or logwood and fustic, and then through sumach; so that it is possible thus to give them the mordant sufficiently in proportion to the iron liquor at first; proceed as in dyeing afterwards, at a heat approaching boiling or even boiling. You may now proceed by adding first the galling or sumach slightly; afterwards the logwood, &c.; and then the remainder of the galling or sumach may be used to finish it; and thus dye the goods black by the quickest possible process.
It should be observed respecting the last process and the process which precedes it, that in dyeing black alum is inimical to the colour. Therefore D'Apligny's is not now esteemed. Alum for black is as improper, as it is proper and essential for red and yellow.
In regard to giving the acetate of iron for black at once, as the second, or London process directs, it may be done by having the proportions full; by full is meant that the mordant should be full enough; then, after the slight galling, as directed in giving the logwood and alder bark decoction, or logwood and fustic, be sure to have that decoction strong enough. This might be called the ground; and the most perfect judgment might be formed of it by having a part of a piece, or one piece of a batch dried in the stove: for, according to the fullness of the ground, so will the black be rich and perfect or otherwise.
The alder bark and fustic are used only to prevent the hue of the logwood from being predominant. If the ground be a full and rich brown, the second full galling or sumaching will bring it to a full and rich black; but, if the ground be poor, these processes will cut or destroy the ground, and the black will be foxy, nasty, and poor; and not only so, but the material dyed will soon wear rotten, because having an over-dose of iron, the iron will tend to decompose the cotton. Therefore the following process is most esteemed.