In curing small skins, where it is not desirable for the fur to come in contact with the liquid, or in the tawing of wool rugs, it is often convenient, after freeing the skin as much as possible from blood and dirt, and adhering flesh, to stretch it on a frame, or nail it out on a board, and apply a strong alum-and-salt solution, as hot as the hand will bear, with a sponge, repeating the operation till the skin is struck through. About 1 lb. of alum and ¹⁄₂ lb. of salt per gallon is a suitable strength. In place of applying the solution, powdered alum and salt is sometimes rubbed into the wet skin. Alumed goods should generally be dried out rapidly, and finally at a good temperature, as this tends to fix the tannage, which is also made more permanent and resistant to water by keeping the skins for a month or more in the alumed condition, an operation known as “ageing.” When first dried, alumed goods are invariably stiff and horny, and, to give them softness, must first be damped back to a half-dry condition, and then gradually softened by mechanical means. “Staking,” and “perching” are the usual methods, the first consisting in drawing the goods vigorously over a bluntish blade fixed on the top of a post, and the second in fixing the skins on a horizontal pole (the “perch”), and working them with the “crutch stake,” a tool formed somewhat like a small shovel with a semicircular blade, in place of which a “moon-knife” (a round blade somewhat like a broad thin quoit) is often fixed in a wooden crutch. The tools, and mode of using them are shown in Figs. 36 and 37.[113] Machines, described on p. 192, are now generally used for these operations. After the first staking or softening, the skins are allowed to become nearly dry, and are then staked a second time. Some judgment is required as to the precise degree of moisture in each case: in the first instance the skins must be sufficiently damp to yield without injury to the mechanical stretching, but in this state they retain sufficient moisture to enable the fibres again to adhere on drying; and at the second staking or perching, they must be damp enough to allow these fibres to be again loosened without violence, and dry enough to prevent their again adhering. [113] The process shown in Fig. 37 is not actually “perching,” but “grounding,” in which a moon-knife with a sharp turned edge is used to reduce the thickness of the skin on the perch, at the same time as it stretches and softens it. [Illustration: FIG. 36.--Staking White Leather.] [Illustration: FIG. 37.--Grounding with the Moon-knife.]