With equal quantities of copper sulphate (blue vitriol), sodium chloride (common salt), well-powdered and mixed together, names or other marks can be etched on steel. The wax process must be used, although soap will answer, or any other substance not coated upon by acids. Spread the beeswax or soap in a thin, even coating, over the article to be etched, and with a sharp-pointed awl, write or draw the design upon the wax-covered surface. Every line must be cut cleanly, and every particle of the coating removed, otherwise a break will appear in the etched line. When the drawing has been made satisfactory, put a "tinker's dam" around the wax-covered spot; this is done by rolling out a piece of putty into a long, thin roll, bend it around the wax-covered spot and press it lightly down, thus making a little reservoir to hold the acid or other corroding substance. Mix up the salt and sulphate of copper, fill inside the dam and moisten with water to hasten their action. When satisfied that the etching is deep enough, or tired of waiting for it to work, wash off the corroding mixture and scrape off the wax, or dissolve it away with turpentine, alcohol or naphtha. If the etching is not deep enough, an ink roller, such as is used on printing presses, may be passed over the surface, a coating of ink put on. This will prevent any acid action upon the surface thus protected, and the solution may be reapplied until the etching is sufficiently deep. If successive etchings are necessary, the plate should be rinsed and warmed after each removal of the corroding solution, and more ink applied before another lot of fresh corroder is put to work.
In regular work, where large numbers of zinc etchings are made, "dragon's blood" is used to protect the surface instead of printer's ink, but for occasional work ink is good enough. Nitric and sulphuric acids may be used for etching, and the effect of the composition described at the beginning of this article depends upon the chlorine and sulphuric acid set free by the combination of the two salts.