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OCR Rendition - approximate
III METHODS OF PRINTING 35 drying materials, such as litharge, which easily part with their oxygen. In finger prints this rapid drying is unnecessary, and the drying materials do harm by making the ink too stiff. The most serviceable ink for our purpose is made of any pure " drying " oil (or oil that oxidises rapidly), mixed with lampblack and very little else. I get mine in small collapsible tubes, each holding about a quarter of an ounce, from Messrs. Reeve & Sons, 113 Cheapside, London, W.C. Some thousands of fingers may be printed from the contents of one of these little tubes. Let us now pass on to descriptions of printing apparatus. First, of that in regular use at my anthropometric laboratory at South Kensington, which has acted perfectly for three years ; then of a similar but small apparatus convenient to carry about or send abroad, and of temporary arrangements in case any part of it may fail. Then lithographic printing will be noticed. In all these cases some kind of printer's ink has to be used. Next, smoke prints will be described, which at times are very serviceable ; after this the methods of water colours and aniline dyes ; then casts of various kinds ; last of all, enlargements. Laboratory apparatus. Mine consists of: 1, slab ; 2, roller ; 3, bottle of benzole (paraffin, turpentine, or solution of washing soda) ; 4, a funnel, with blottingpaper to act as a filter ; 5, printer's ink ; 6, rags and duster ; 7, a small glass dish ; 8, cards to print on. The Slab is a sheet of polished copper, 10 2 inches by 7, and about 1 inch thick, mounted on a solid board 4 inch thick, with projecting ears for ease of
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