COPYING-3IACIIINES (ante). 1. The Electric Pen, invented by Thomas A. Edi son. This is a metallic tube or style within which vibrates longitudinally a steel wire, pointed and protruding slightly at the lower end. The vibration is caused by an engine carried at the top of the style. Several motive powers are applicable, as compressed air, water, force communicated from other machinery, etc.: but as the most convenient and portable, Mr. Edison chose an electro-magnetic engine, actuated by a current brought from a small battery which stands on the table by the side of the writer. The engine having been started, and the wire vibrating at a rapid rate, the style is held ver tically over the paper, and the point is moved upon the sheet as in the act of writing. The needle punctures a series of holes in the path over which the pen is carried, and the paper becomes a stencil, in which the writing readily appears when the sheet is held up to the light. This stencil is then laid upon a sheet of plain paper, in a frame which binds the two together; an inked roller is passed over it., and the ink pressed through the holes in the stencil appears upon the clean sheet in a series of minute dots in the line of the writing. With careful use a stencil will furbish 500 or more copies. After some copies have been taken, the stencil may be dried and kept for use again.
2. The Papyrograph. The patentee furnishes a specially prepared paper, upon which words are written with a common pen, but with a special ink. The sheet is then soaked in water, and the ink corrodes the fabric of the wet paper, leaving open lines in place of the writing. The sheet is then used as a stencil, like that prepared by the elec tric pen.
3. 2'he Gelatine Pad. A simple, cheap, and copier may be prepared thus: Procure a shallow tin pan, one half an inch deep, and a little larger than a common cap or letter sheet. Soften 3 oz. of gelatine, white ghee, or even common glue, by soaking in cold water, and remove all the unabsorbed water. Boil for 1 hour in 10 oz. of cerine, over a salt-water bath, and pour into the pan; when cold it is ready for use. In warm weather a larger proportion of glue is desirable. A special ink is necessary. Boil 1 oz. of violet aniline in 7 oz. of water; when bold, add 1 oz. of alcohol, -I oz. of ether, t oz. of glycerine, and 2 or 3 drops of weak carbolic acid. If this ink dries too quickly in the pen, add a few drops of alcohol. A good ink is made by dissolving 2 oz. of citric acid in 6 oz. of water, to which add 1 oz. of violet aniline. The writing to be copied is laid face downward upon the pad, and lifted again after a moment's delay, when a copy appears in reverse upon the jelly. A clean sheet laid upon this negative and instantly removed, shows a facsimile of the original. Success depends much upon the quality and consistency of the ink. Ink made with black aniline will give about ten copies; with green, 30; with red, GO; and with violet aniline 100 to 125 fair copies have been taken. As soon as the copying is finished, the pad should be 'washed, using a soft
sponge and clear water, warm preferred. The action of the pad is thus explained: The glue does not unite with the glycerine, but forms a spongy mass whose minute pores are occupied with the fluid. The aniline ink is absobed by the glycerine and given pp suc cessively to the sheets of paper, as they are laid down. Repeated washings wear away the pad. If its surface becomes injured it may be remelted, and more material added, at pleasure. Pads of this nature, made from various recipes, are sold under different names, but the materials and methods of use are substantially as described.
4. The Blue Process is peculiarly adapted to the reproduction of drawings, and is useful to architects, engineers, and artificers. Two solutions are prepared: the first contains one part of citrate of iron in four parts of pure water; the second contains one part of red prussiate of potash in six parts of water. When ready for use, equal parts of the solutions may be mixed in a shallow dish, and applied to sheets of paper with a sponge or a camel's hair pencil. Any paper will serve, but that is best which has but little sizing. The solution should be applied, and the paper should be dried and kept in the dark. The solutions themselves will keep, separately, in the dark as long as desired, but if mixed soon begin to deteriorate. The drawing or writing to be copied should be made with very black ink, upon paper or tracing cloth. A photographer's glazed frame, having a back easily removed, is useful' for copying. Place the drawing face down upon the glass; the prepared paper with its face against the back of the drawing; put the movable back in place, reverse the frame, and expose to light. In direct sunshine, 2 to 7 minutes will be long enough, the time to be ascertained by trial; in diffused light, the exposure must be 5 to 10 times as long. After exposure the print should be imme diately washed in a tub of clear water; when the chemicals are removed, the sheet is fastened by its corners to a line to dry, and the surface may be afterward finished by a hot iron, or by pressure. A little practice may be needed to secure the best results, in which the lines will he clear white, and the background a deep blue. A light blue background indicates a weak solution, or insufficient exposure; over-exposure is shown by a grayish tint. Clear, quick sunshine will give sharper lines than can be obtained by slow diffused light. The chemical change is evident; the light causes a reaction between the prussiate of potash and the iron, of which Prussian blue is the product; this occurs wherever the light has not been intercepted by the black lines of the drawing, which therefore appear in white upon an intensely blue and unfading background. Copies may be multiplied at will from negatives in collodion on glass, from engravings in books, from drawings, or from manuscript.