The amount of acid to be used may vary between considerable limits without affecting the results. If too much is present, there is danger of injuring the feel and the lustre of the fibre. If there is not enough acid in the bath, the color will wash right out of the wool, as soon as it is rinsed. In general it is well to start with about one tablespoonful of dilute (30%) sulphuric acid for each gallon of dye-liquor and about twice that amount of Glauber’s salt.
It is hard to tell just what is the function of the Glauber’s salt. It seems, however, to open up the pores of the wool in some way, and to make it dye more evenly and deeply. The bath is gently heated, with constant stirring of the goods, until the right shade is produced, or, if it is desired to exhaust the bath and so waste no color, until near the boiling point.
The goods when taken out of the dye-bath must be washed very thoroughly, to remove the last trace of acid, which otherwise on drying would ruin the wool.
It must be remembered that these Acid dyes hardly affect cotton in the least, and so the goods dyed in this way must be free from vegetable fibres, if level dyeings are to be obtained.
In dyeing wool skeins commercially it is, of course, of the utmost importance to have the colors perfectly level and uniform. This uniformity is obtained easily enough, when using these Acid dyes, by having the wool thoroughly wet before placing it in the dye-bath; by having it well loosened out and well stirred so that the color will penetrate evenly every part of the material; and, finally, by starting the bath at a moderate temperature, and heating it gradually, until the proper shade is obtained.
For handicraft dyeing the student is strongly advised to practise shaded and irregular effects, the so-called Rainbow dyeing, with wool in skeins, just as, in previous lessons, with raffia and with cotton. By using coarse heavy yarns, very beautiful two and three color effects can be produced, which, when used for embroidery or weaving, will prove most interesting.
Great care must always be taken, in wool dyeing, to preserve the lustre and the soft effect of the wool, and to avoid felting. This can best be done by using moderate amounts of acid, by dyeing at moderate temperature and never raising the dye-bath quite to the boil; and finally, by handling the goods as little as possible in the acid dye-bath, consistent of course with exposing every portion equally to the action of the dyestuff. Cotton skeins can be worked and rubbed, and pulled, and thrown up and down in the hot dye-bath, without fear of injuring them. But wool should be handled carefully, and worked in the dye-pot quietly and gently, just sufficiently to accomplish two results. First, the wool at the bottom of the pot should be raised by a lifting and turning motion and replaced by fresh material; and second, when the wool is lowered back into the liquor it should be loosened, so as to allow the dye-liquor to penetrate the mass.
Chapter IX
DYEING FEATHERS
The use of feathers and, especially, of ostrich feathers for millinery has, during the past few years, increased to enormous proportions. Besides the home product, from California and the Western States, which, however, is but small, the importation of raw feathers from abroad has averaged, during the past two or three years, nearly eight millions of dollars. As yet, the dyeing of these feathers is almost entirely confined to professionals—their processes, although simple, not being generally known or published.
As before mentioned, feathers, like other animal products, can be colored with ease by either the Basic or the Acid dyestuffs. In practice, as with wool and silk, the Acid dyes are universally used, because of their greater variety, their greater fastness to light, and their better levelling properties. To use the Acid colors with success the following points must be carefully considered. First, the baths must be such as not to ruin or “burn” the feathers, i.e., they must leave intact the tiny barbules upon the barbs or “flues,” as the dyers call them, which make the feather look soft and full and not stringy.