Etching is the art of cutting lines in any material by means of some corrosive agent. Thus, since nitric acid dissolves copper, if we confine the action of the acid to certain lines, we can cut grooves of considerable depth in the copper, and these grooves may be used either as lines from which we may print, or as marks similar to writing. Iron, brass, steel, silver, ivory, glass, marble, and many other materials may be cut in the same way, by the action of suitable acids. As a simple and easily learned method of forming engraved plates from which to print, the art of etching is one of the most eligible for young persons. The materials required are few and simple, great freedom of outline may be secured; and the results are very pleasing.
Copper is the metal usually employed for etching drawings. It is furnished by the dealers in plates perfectly smooth and flat, and of any desired size. The surface is first coated with a wax or varnish, for which there are many recipes, the following being probably the best: Take of beeswax and asphalt, 2 parts each; Burgundy pitch and black pitch, 1 part each. Melt the wax and the pitch in an earthen vessel and add the asphalt by degrees in fine powder. Expose to heat until a drop which has been cooled, breaks by bending back and forth two or three times in the fingers.
A second, which is simpler and said to be very good, is composed of asphalt, 2 oz.; Burgundy pitch, 1 oz.; beeswax, 1 1/2 oz.
A transparent varnish may be composed of resin, 1 oz.; beeswax, 2 oz. Melt together.
The plate having been polished and burnished, is grasped by one corner in a hand-vice and warmed over a spirit lamp until it will melt the varnish or etching ground, which is then spread over its surface very thinly by means of a ball or pledget of cotton tied in a piece of silk. Before the ground has quite cooled and solidified, it is blackened by the smoke of a lamp or candle. The blackening is necessary so that the design may be clearly seen as it is drawn in.
The design may be either drawn directly on the plate, or transferred by means of transfer paper. Or it may be first drawn on the etching ground by means of a very finely pointed camel-hair pencil, using, of course, a white color dissolved in some medium which will adhere to the ground. Water is useless. Turpentine answers very well.
In whatever way the design is drawn on the surface of the ground, it must next be cut in by means of a steel point, good sewing needles making excellent ones, and different sizes being used according to the strength of the lines required. The lines having been traced through the varnish so as to expose a bright copper surface, the next step is to make a border of wax around the plate so that the acid will not run off. The wax used for making the border is a mixture of beeswax, resin and tallow, of such a consistency that it will be easily moulded by the fingers. The border should be nearly half an inch high, thus converting the plate into a shallow dish. This dish is half filled with a mixture of one part of nitric acid and three parts of water. After this plate has been exposed for a few minutes to this liquid, the acid is poured off, the plate washed with pure water and allowed to dry. All the very delicate lines are then " stopped " out, as it is called, by being coated by means of a camel-hair pencil with varnish dissolved in turpentine. When this has dried, the acid is poured back again and allowed to act on the coarser lines, and the more frequently this process is introduced, the more perfect will be the ultimate result.
When the lines have all been etched to the required depth, the varnish is removed by warming the plate and washing with turpentine. A copper-plate press is used to take off the impressions.
The process of etching is very simple, and the results very satisfactory. As an artistic recreation, it is capable of afford' ing a great deal of pleasure.
The art of cutting names, etc., on steel tools and other objects, is very simple and useful. The following gives good results:
Mix 1 oz. sulphate of copper, 1/4 oz. of alum, and 1/2 a teaspoonful of salt reduced to powder, with 1 gill of vinegar and 20 drops of nitric acid. This liquid may be used either for eating deeply into the metal or for imparting a beautiful frosted appearance to the surface, according to the time it is allowed to act. Cover the parts you wish to protect from its influence with beeswax, tallow, or some similar substance.