The use of the brush method in applying the natural dyes to furs is limited to a comparatively few kinds of dyeing, namely to produce special effects on furs, or to give to the upper-hair of furs a coat of dye different from the base color. In a quite recent German patent is described a process for blending a red fox as a silver fox and the procedure affords a good example of brush dyeing with preliminary mordanting. The specification is as follows: “D. R. P. 310, 425 (1918). A process for dyeing red fox as silver fox. The tanned and dressed skin is first superficially decolorized by applying a dilute mixture of milk of lime, iron vitriol and alum, with a soft brush so as only to penetrate the top-hair. Allow to remain for 4–6 hours, dry, and beat out the dust. A dilute solution of iron vitriol is brushed on so as only to wet the top-hair, and the skin is thus allowed to remain moist for 12–24 hours. Then without drying, a solution of iron vitriol, salammoniac, litharge, red argol and wood ashes is brushed on cold with a hard brush so as to penetrate all the hair down to very near the skin. The skin has now completely lost its red color, and has become a pale yellow. It is now ready to be dyed. An infusion of roasted nutgalls, which have been boiled for 3–4 hours with water, is applied cold with a soft brush to the upper hair. Allow to remain so for 2–3 hours, and without drying, apply a weaker solution of the roasted nutgalls with a hard brush so as to saturate the hair thoroughly. Dry and beat out. According to the concentration of the solution applied, the hair will be colored blue-grey to black, and the shade can be varied by varying the strength of the solutions used. The different parts of the skin, or those parts of different shades can be dyed accordingly.” In this patent all the operations, including killing, mordanting and dyeing are done by the brush method, and the process, from this point of view is quite similar to one which might have been employed a century previous. It is evident that the time and effort required to carry out the details as described in the patent would only be warranted in exceptional cases, where the value of the dyed fur would be considerably greater than that of the natural skin. An example of the application at the same time of dye and mordant by the brush method is the original French Seal dye, which is still employed to a limited extent to produce a brilliant, deep, lustrous black topping on furs which have already been dyed by the dip process. A typical formula for the old French Seal dye is the following: Green copperas 10 parts Alum 10 „ Verdigris 10 „ Gall-nuts 80 „ Logwood extract (15 degrees Twaddell) 150 „ Water 1000 „