The formulas for other shades were made up along similar lines, the chief constituent of vegetable nature being either gall-nuts, sumach, or both. A mixture for a chestnut brown, for example, contained gall-nuts, sumach, and the various other mineral constituents as in the black dye, litharge, alum, copperas, verdigris, salammoniac, antimony, and in addition, red lead and white lead. It is evident in both these instances that the shade obtained was as much the result of mineral dyeing as of vegetable dyeing.
The discovery of America introduced into Europe many new dye substances, chiefly wood extracts such as logwood and Brazilwood, but it was not until the nineteenth century that these materials found their way into the dye formulas of the fur dyer. Most of the processes used in the dyeing of furs were adaptations of methods employed in silk dyeing, the silk fibre being considered as most nearly approaching fur-hair in nature and characteristics. By devious and circuitous paths the formulas of the silk dyers reached the fur people, and so, in the middle of the nineteenth century, dye mixtures containing the various dyewoods as well as the tannin-containing substances were in general use for the dyeing of furs. The following is a typical recipe of that time for the production of black on furs like wolf, skunk, raccoon, etc.:
| Roasted gall-nuts | 1000 | parts | |
| Sumach | 200 | „ | |
| Iron mordant | 200 | „ | |
| Copper vitriol | 100 | „ | |
| Litharge | 80 | „ | |
| Alum | 60 | „ | |
| Salammoniac | 50 | „ | |
| Crystallized verdigris | 40 | „ | |
| French logwood extract | 30 | „ | |
| Rain water | 7000 | „ |
The mixture was boiled up, and after cooling was ready for application by the brush method, the skins being first killed by a killing mixture also applied by the brush. The dye substances in this case are the gall-nuts, sumach and the logwood extract, with the iron mordant, copper vitriol, and alum as mordants. For brown shades a similar formula was used containing Pernambuco wood extract, logwood extract, quercitron bark, gall-nuts and dragonblood, together with iron, copper and alum mordants.
Formulas such as the above were mainly empirical, that is, they were compounded as a result of trial of various combinations of the constituents, without considering the nature and quantitative character of the reactions, as long as the desired shades could be obtained. Such dye mixtures were frequently found to yield results varying from those expected or originally obtained, because the effectiveness of the formulas depended upon the exact duplication in every detail, of conditions which had given satisfactory results previously, and it was not always possible to attain such an accurate reproduction of circumstances, especially when the fur dyers were quite ignorant of the scientific relationships of the materials used. So when more light had been shed on the nature and chemical characteristics of the vegetable dye substances, formulas like those described were no longer employed, although the essential ingredients were the same in the new processes. Unnecessary constituents were eliminated, and proper ones substituted where it was required, and the quantities of the materials used were made to conform to the chemical laws governing the reactions. Since these new formulas were based on a rational understanding of the constituents and their reactions, it is desirable to study the latter briefly, before further discussing the formulas themselves.
The substances of vegetable origin used in modern fur dyeing may be grouped into two classes, one, the tannin-containing materials, and the other, the dyewoods proper. The most important of the tannins are gall-nuts, sumach and chestnut extract. Cutch, which also comes under this class, is more frequently used for the production of brown shades, so it is grouped with the dyewoods. Among the latter are logwood, fustic, Brazilwood, quercitron, turmeric, and several others of less significance.
1. Tannin Materials
First and foremost under this heading are the nutgalls. These are ball-shaped excrescences produced on certain plants by the punctures of insects in depositing their eggs. There are two chief varieties, the European, and the Chinese. The European galls are formed by the female gall-wasp which drops an egg in the rind of young branches of certain oaks. A swelling (the nutgall) is produced, in which the young insect develops, and from which it finally escapes by piercing a hole through the shell. Those galls which are not pierced have a fresh bluish or green color, are heavy and contain most tannic acid. After the insect has gone out, the galls are of a lighter, yellowish color, and also of inferior quality. The best oak-galls are the Aleppo, and the Turkish or Levant galls, containing 55–60% of tannic acid, and about 4% of gallic acid. The Chinese galls are produced by the puncture of a plant-louse on the leaves and leaf-stalks of a species of sumach, and not on oaks. The galls are very light, and very rich in tannic acid, containing often as much as 80%. For dyeing purposes, nutgalls are usually ground to a powder, and in some instances they are even roasted first and then ground.
Sumach consists of the leaves and sometimes of the small twigs and stems of a species of sumach plant known as the Rhus coriaria. The Sicilian variety is the finest commercial quality, with the Virginian ranking next. It is sold as a powder, but also in the form of the whole or crushed leaves. The best sumach contains 15–25% of tannin. Extracts are also manufactured, a liquid extract of 52 degrees Twaddell, which forms a dark brown, thick paste; and a solid extract, formed by evaporating the liquid extract to dryness.
Chestnut extract is prepared from the wood of the chestnut oak, which contains 8–10% of tannin. The solid extract has a bright, black color, while the liquid extract is a dark brown paste with a smell like that of burnt sugar.