Dilute one ounce of gum-asphaltum with a pint of spirits of turpentine, in the manner described at 51;—put this into a flask, and add one ounce of gum-elastic cut into very small pieces, and half an ounce of gum-shellac previously reduced to powder. Suspend the flask unstopped over a fire of charcoal, or set it in a sand bath where it may boil gently till the quantity is reduced to a gill; then strain it through a flannel, and when nearly cold, bottle and cork it. The leather should be thoroughly blackened with some liquid blacking and waxed over slightly with bees-wax before the elastic blacking is applied. If the blacking should be too thick, it may again be diluted with spirits of turpentine. It should be warmed when applied, and the work may require several coats, and a considerable time for each to dry. Any of the above mentioned gums may also be dissolved in sulphuric ether, and thus produce a fine drying varnish, but the preparation is much more difficult as the volatile nature of the ether will not admit of much heat, whereby to facilitate the solution.