PARCHMENT, VEGETABLE, is a substance lately brought into notice, as an important addition to the materials for manufactures. It is in fact, paper, but paper so altered as to possess many of the qualities of parchment. Messrs. Mongolfier, of Paris, have a mode of so preparing paper as to convert it into a kind of parchment, applicable, among other purposes, as a substitute for goldbeaters'-skin ; but Mr. Caine's vegetable parchment is a different substance. As described before the Royal Institution, in 18.57, it appears to bo paper altered in its textural qualities by the action of sulphuric acid. (Paternie.) Very little more is required than dipping a sheet of paper into the acid ; but then the strength of the acid must be exactly determined. The peculiar effects of acids and alkalies on paper were known long before—as in Kuhlmann 's pyroxylised texture. Pelouze's gun paper, and Mercer's process for fibrous textiles; but Mr. Gaine's success depends mainly on the adoption of one particular strength of sulphuric acid, mixed with half its bulk of water. A sheet of paper being dipped in this liquid, it is almost instantly changed in character. It. becomes tough, hard, and fibrous, without any alteration of weight. It gives a writing surface far bettor than that of animal parchment. It receives oils and varnishes freely. It bears rubbing better than any kind of paper, and almost as well as sheepskin. It will serve as a substitute for vellum in book binding ; as a material for policies, certificates, &o. ; ns a strong paper for echool-books : and as covering for jars and bottles of various kinds. Ordinary paper, even after being printed on, can be converted into this vegetable parchment. The substance is so strong. that a ring seven
eighths of an inch in width, and weighing only 28 grains, is said to bear a suspended weight of 92 lbs.
Soon after Mr. Caine's process became known, and commercially introduced by Messrs. Do la Buts, Mr. W. Crookos made experiments to determine its possible or practicable relation to photography. Ho passed slips of pepeaphotograplis through acid of the required strength, and found that the colours and tints, even in the delicate linif.tones, remained intact ; that the uniform contraction of the paper added materially to the sharpness of the picture ' • that the paper became much stronger than before; that it would rough 'handling imme diately, without tearing ; that the non-albumenised photographs acquired a peculiar glossy appearance, giving a rich finish without glare ; and that the picture might bo washedavith soap and water, and rubbed with a cloth, without injury.
Professor Muschamp, of Wurtemberg, has devised a mode of making paper waterproof, without, however. giving it those qualities which belong to vegetable parchment. He dissolves 24 oza. of alum and 4 OM Of WhitO soap in 2 lbs. of water ; also, 2 ozs. of gum amble, and 6 ors. of glue, in 2 lbs. of water ; the two solutions are mixed, and the shoots of paper dipped into the mixture while warm. Tho shade are hung tip till dry, and sometimes also passed between rollers. The paper thus prepared is intended for packages exposed to the weather.