Note 4 — Chapter II

(p. 11.) I wrote to M. Lalanne to find out the ingredients of the petit vernis liquide and vernis au pinceau, but he says that he does not know, and that the recipes are a secret of the maker of these varnishes. The asphaltum varnish mentioned on p. xvi and in Note [3] does excellently well, however, both for stopping out and retouching. After it has been fanned (see p. xxi) until it has thickened sufficiently not to stick to the finger when touched, but before it is quite dry, it can be worked upon with the point. If not dry enough, which will manifest itself readily as soon as you have drawn the first line, fan again. If it were allowed to dry absolutely, it would chip off under the needle. There is a liquid ground, made by Mr. Louis Delnoce of the American Bank Note Company, New York, which—so Mr. Jas. D. Smillie informs me—is used for retouches by the engravers of the company, is applied with the brush, is a very quick dryer, tough, and resists acid perfectly. Mr. Delnoce sells it in ounce bottles at seventy-five cents each.