685. Wash for preserving Drawings made with Black Lead Pencil, or with hard Black Chalk.—A thin wash of isinglass will fix either black lead or hard black chalk, &c., so as to prevent their rubbing out; or the same effect may be produced by the simple application of skimmed milk. The best way of using the latter, is, to lay the drawing flat upon the surface of the milk, and then, taking it up expeditiously, to hang it by the one corner till it drains and dries. The milk must be perfectly free from cream, or it will grease the paper.
686. To make Red Sealing Wax.—To every ounce of shell-lac take half an ounce each of resin and vermilion, all reduced to a fine powder. Melt them over a moderate fire; and when thoroughly incorporated and sufficiently cool, form the composition into what are called sticks. On account of the dearness of shell-lac, seed-lac is usually substituted. A more ordinary sort, but sufficiently good for most occasions, may be made by mixing equal parts of resin and shell-lac with two parts of red lead and one of vermilion. In a still commoner sort, the vermilion is often entirely omitted.
MARKING INK.
687. Mix in six drachms of distilled water, two drachms of sub-nitrate of silver, and two drachms of gum-arabic. For the mordant, mix with four ounces of water, half an ounce of gum-arabic, and half an ounce of sub-carbonate of soda. The article to be marked should first be wetted with the mordant, and pressed smooth, and should be thoroughly dried before it is written upon. The mark should be exposed to the light for some time, to become black.
688. Permanent Red Ink for marking Linen.—This useful preparation, which was contrived by Dr. Smellie, of Edinburgh, who was originally a printer in that city, may be used either with types, a hair pencil, or even with a pen: Take half an ounce of vermillion, and a drachm of salt of steel; let them be finely levigated with linseed oil, to the thickness or limpidity required for the occasion. This has not only a very good appearance, but will, it is said, be found perfectly to resist the effects of acids, as well as of all alkaline leys. It may be made of other colors, by substituting the proper articles instead of vermillion.