This Dutch mordant is preferred to nitric acid by many etchers,—even when working, not in the bath, but in the ordinary way, as taught by M. Lalanne,—because it bites down into the copper, and hardly widens the lines. “From my experience,” writes Mr. Jas. D. Smillie, in a letter now before me, “I unhesitatingly prefer the Dutch mordant for copper; it bites a very fine black line, it is not so severe a trial to the ground, and it does not need constant watching.”
Mr. Smillie, however, uses the mordant much stronger than Mr. Haden. He has, in fact, invented a process of his own, which, in a letter to me, he describes as follows:—
“I draw and bite as I progress; that is, I draw in the darkest parts first, give them a good nip with the mordant, wash the plate and dry it, and then draw the next stage. I can thus, by drawing lines over a part that has already been exposed to the mordant, interlace heavy and light lines in a way that I could not by any other process. I etch upon an unsmoked ground, and as the Dutch mordant bites a black line, I see my etching clearly as it advances, By holding the head well over the plate, the lines can be very distinctly seen as they are drawn. After a little experimenting, the etcher will find the angle at which he can see his unbitten work upon an unsmoked ground without trouble. Mr. Hamerton's formula seemed to me too weak, so I am experimenting with
| Muriatic acid, | 1 | ounce. |
| Chlorate of potash, | 1-5 | „ |
| Water, | 5 | ounces. |
“This is the mordant I am now using, and I have found it to work well. Still, as I am not a scientific chemist, and my knowledge is entirely empiric, I am prepared to believe any chemist who may tell me that I might do as well, or better, with more water.
“Generally I do not get all the color I wish by the first process, as I can see without removing the ground; so, when my etching is finished, I reverse the engine and begin stopping out and biting upon the original ground, as it is ordinarily done. I do not use the black asphaltum varnish for stopping out, but a transparent varnish that is simply white resin dissolved in alcohol. If applied very carefully, and allowed time to dry, it is perfectly clear and transparent, and the relations of all parts of the plate can be seen,—the stopped out as well as the bitten lines,—but to a careless worker it presents many troubles. It is so transparent that it is hard to see what is stopped out and what is not, and if washed with very warm water, or before it is thoroughly dry, it turns cloudy and semi-opaque. I have no trouble with it, and could not get along without it. I make it myself,—have no formula,—adding alcohol until it is thin enough to flow readily from the brush. It has a great advantage over asphaltum varnish, as it does not flow along a line. It is viscid enough to remain just where it is put, and is as perfect a protection as any asphaltum varnish.”
Mr. Smillie heats his bath on the plate-warmer, but not to exceed 80°, or at most 90°. Such a bath of hot mordant acts much more quickly than a cold acid bath, less than two minutes being sufficient for the lightest lines.
(p. 50.) Gravers are of different shapes, according to the nature of the line which they are intended to produce. They are sometimes kept at the hardware-stores, as, for instance, by A. J. Wilkinson & Co., 184 Washington St., Boston. This house also issues an illustrated catalogue of engravers' tools.