For some processes there is needed an etching ground which has the property of not coating the entire surface, permitting the etching fluid to penetrate at many spots uniformly, or, if it resists the etching fluid, still so easily affected by manipulation that it will admit the acid according to such manipulation. There are two ways to make it. (1) Thick linseed oil varnish 1 part Tallow 2 parts (2) Wax 1 part Tallow 5 parts Linseed oil varnish 3 parts The application will be described in the instructions about aquatints, etc. VII ACID PROOF INK So I name a color which has the property of resisting acid when the stone is inked with it. It is useful in many cases, and even necessary. It is well, therefore, to make a supply of it. 2 parts thick linseed oil varnish 4 parts tallow 1 part Venetian turpentine 1 part wax All must be well melted, mixed with four parts lampblack, well rubbed down and kept in a closed tin vessel. VIII CRAYON Chemical or fatty crayon is a composition intended to be used on the stone plate in dry form like Spanish or Parisian chalk. The inks described previously have the property of soaking into the stone and making it greasy where applied. The same happens if they are applied dry, the degree of their penetration and adherence merely being less. The mixtures that may be used to make crayons are countless. Wax and soaps, however, are better than resinous materials. Therefore it is likely that the compositions here named will be pretty nearly the best. (2) Wax 4 parts Soap 6 parts Lampblack 2 parts, roasted, or better still, made as explained before. The wax and soap are melted together. The lampblack is added then. All is rubbed down fine on a hot plate, and then placed on the fire again till it is fluid once more. Then it is poured on a stone plate coated with a little oil, so that it forms a cake of about one eighth inch thickness. When this has cooled a little, it is cut into thin pieces and put away till needed. (2) Wax 8 parts Soap 4 parts Lampblack 2 parts Burn the wax till one half is consumed, then melt the soap with it, and treat the mixture as before. (3) Wax 4 parts Spermaceti 4 parts Soap 4 parts Lampblack 2 parts The first three materials are melted together, the lampblack is added, and then the whole is treated as before. (4) Wax 8 parts Spermaceti 4 parts Soap 4 parts Lampblack 2 parts The wax is to be half burned away, then the spermaceti and soap are to be melted into it, and the whole treated as the other formulas.