Photo-Lithographic Transfer Paper.
Photo-lithographic transfer paper and ink are prepared in the following manner:—The paper is treated with a solution of a hundred parts of gelatine and one part of chrome alum in 2,400 parts of water. After drying, it is treated with the white of egg. It is made sensitive with a bath consisting of one part of chrome alum, 14 parts of water and 4 parts of alcohol. The latter ingredient prevents the white of egg from dissolving. On the dark places the white of egg, together with the ink with which the exposed paper has been coated, separates in water. The transfer ink consists of 20 parts of printing ink, 50 parts of wax, 40 parts of tallow, 35 parts of colophony, 210 parts of oil of turpentine, 30 parts of Berlin blue. It is found that a varnish formed of Canadian balsam, dissolved in turpentine, supplies a most valuable means of making paper transparent. The mode by which this is most satisfactorily accomplished is by applying a thin coating of this varnish to the paper, so as to permeate it thoroughly, after which it is to be coated on both sides with a much thicker mixture. The paper is kept warm by performing the operation before a hot fire, and a third and even a fourth coating may be applied until the texture of the paper is seen to merge into homogeneous translucency. Paper prepared according to this process is said to come nearer than any other to the highest standard of perfection in transparent paper. Care must be used in making, as the materials are highly inflammable.
Different Kinds of Engraving.
“Line” engraving is of the highest order. All engravings are done in “line”—simply straight lines. Next comes “line” and “stiple.” “Stiple” means dots—small dots like this:—....—.... These small dots are used to lighten up the high parts of the face or drapery. It is very hard to engrave a face in lines, simply, and only master engravers have ever undertaken it. The masters understand and practice both in “line” and “stiple.” Claude Mellan engraved, in 1700, a full head of Christ, with one unbroken line. This line commenced at the apex of the nose, and wound out and out like a watch spring. Mezzotint engravings are produced thus:—The steel or copper is made rough like fine sand paper. To produce soft effects, this rough surface is scraped off. If you want a high place or “high light” in your engraving, scrape the surface smooth, then the ink will not touch it. If you want faint color, scrape off a little. Such engravings look like lithographs. Etching is adapted to homely and familiar-sketches. Etching is done thus:—The copper or steel plate is heated and covered with black varnish. The engraver scratches off this varnish with sharp needles, working on the surface as he would on paper with a pencil. Nitric acid is then passed over the plate, and it eats away at the steel and copper wherever the needle has scraped off the varnish. When the varnish is removed with spirits of turpentine, the engraving is seen in sunken lines on the plate.
How to Preserve Pencil Sketches.
The pencil drawings of mechanical draughtsmen and engineers may be rendered ineffaceable by the following process:—Slightly warm a sheet of ordinary drawing paper, then place it carefully on the surface of a solution of white resin in alcohol, leaving it there long enough to become thoroughly moistened. Afterward dry it in a current of warm air. Paper prepared in this way has a very smooth surface. In order to fix the drawing, the paper is to be warmed for a few moments. This process may prove useful for the preservation of plans or designs when the want of time or any other cause will not allow the draughtsman reproducing them in ink. A simpler method than the above, however, is to brush over the back of the paper containing the charcoal or pencil sketch with a weak solution of white shellac in alcohol.
Care of Wood Type.
Wood type should always be kept in a cool and dry place—not, as is often the case, a few feet from a large stove, or directly over the lye and wash tub. The drawer or shelves—drawers or cases are preferable to shelves—where they are kept, should not, as very often happens, be made of unseasoned wood, for this reason: type wood is usually perfectly seasoned, and when allowed to remain for any length of time on a damp surface, the moisture is absorbed, the bottom expands, and a warped type, ready to be broken at the first impression, is the result.
Wood type should only be washed with oil. A moistened cloth is sufficient, is more economical, and is certainly much cleaner than using their weight in oil. All wood type have a smooth and polished face, and if properly cleaned when put away will last for years. In fact, proper use only improves the working qualities. Wood type forms should not be left standing near hot stoves, or left locked up over night on a damp press or stone to warp, swell, and perhaps ruin a costly chase.