3159. Simple Method of Copying Drawings, Etc

3159.      Simple Method of Copying Drawings, Etc. Silvered albumen paper, after being washed, may be conveniently used for copying negatives as well as positives. It keeps for weeks, and becomes sensitive to light only after exposure to the vapors of aqua ammonia, technically termed smoking with ammonia. Dr. H. Vogel has greatly simplified the latter process by substituting for the liquid ammonia the powder of carbonate of ammonia. He thoroughly impregnates a piece of felt or cloth with this powder, and lays it under the silvered sheet, separated from it by a piece of blotting-paper. He places the silvered paper, with the substratum of carbonate of ammonia and the drawing on top, between two plates of glass, and, exposing it to the light of the window, obtains a copy quite distinct in all its details. The copy obtained is, of course, in white lines upon black ground. Such photographs require to be treated with soda when intended for long preservation.

3160. Lea's Solution for Cleaning Photographic Glasses

3160.     Lea's Solution for Cleaning Photographic Glasses. Water, 1 pint; sulphuric acid, 1/2 ounce; bichromate potash, 1/2 ounce. The glass plates, varnished or otherwise, are left, say 10 or 12 hours, or as much longer as desired, in this solution, and then rinsed in clean water, and wiped or rubbed dry with soft white paper. This preparation is by Mr. Carey Lea, of Philadelphia, and is said to be the best in use. It quickly removes silver stains from the skin without any of the attendant dangers of the cyanide of potassium.

3161. Wenderoth's Photographic Varnish

3161. Wenderoth's Photographic Varnish. Nearly all photographic varnishes reduce the intensity of the negative. Mr. F. A. Wenderoth, of Philadelphia, states that if a thin solution of gum-arabic is applied to the negative after fixing and before drying, the varnish will not affect the intensity. This is a very simple and useful remedy. Mr. "Wenderoth also states that he has long practiced the covering of photographic paper prints upon both sides with collodion varnish, and finds it a complete preservative of the picture. Nearly all photographs will fade away in a few years unless thus protected.

3162. Collodion Varnish for Photographic Prints

3162. Collodion Varnish for Photographic Prints. A very effective and agreeable polish is communicated to card or cabinet prints, etc., simply by coating them with a glutinous plain collodion, made as follows: Alcohol, 3 ounces; ether, 4 ounces ; pyroxyline, 42 grains. Dissolve and filter in the usual manner. The prints are first cut to the proper size and floated on the reverse side upon clean water until they lie perfectly flat; then take one print at a time and place it on a piece of glass of the same size as itself, moist side downwards; it easily adheres to the glass. Let the excess of water drain off, and remove all moisture from the picture surface; now coat it with the collodion and let it drain in the usual way, then dry it before the fire or in any manner which is most convenient. This polish is not so flagrant on the one hand as the so-called enamel surface, nor so dead as an ordinary albumen print that has undergone all the operations up to the mounting.