This process, as you see, is very accommodating; but it is too much like mezzotint or aquatint, and, furthermore, it can only be applied in flat tints, without modelling. I have, nevertheless, explained it to you, so that you may be able to use it, if you should have a notion to do so, as a matter of curiosity, but with reserve. It is better to use the dry point, which has more affinity to the processes natural to etching.
Pl. V.
78. Mottled Tints.—You may also make use of the following process (but with the same restrictions) in the representation of parts of old walls, of rocks and earth, or of passages to which you desire to impart the character of a sort of artistic disorder:—Distribute a quantity of ordinary etching-ground on a copper plate sufficiently heated; then take your dabber, and, having charged it unequally with varnish, and having also heated your etched plate, press the dabber on the passages which are to receive the tint; the varnish adheres to the plate in an irregular manner, leaving the copper bare here and there. Now stop out with the brush those parts which you desire to protect, and bite in with pure acid; the result will be a curiously mottled irregular tint (see [Pl. V.] Fig. 2). Properly used in the representation of subjects on which you are at liberty to exercise your fancy, this process will give you unexpected and often happy results.
79. Stopping-out before all Biting.—Before we proceed, I must show you an easy method of representing a thunder-storm (see [Pl. V.] Fig. 2):—Work the sky with the needle, very closely, so as to get the sombre tints of the clouds; and, before biting, trace the streaks of lightning on the etched work with a brush and stopping-out varnish; being thus protected against the acid, these streaks will show white in the printing, and the effect will be neater and more natural than if you had attempted to obtain it by the needle itself, as you will avoid the somewhat hard outlines on either side of the lightning, which would otherwise have been necessary to indicate it.
You can employ the same process for effects of moonlight, for reflected lights on water, and, in fact, for all light lines which it is difficult to pick out on a dark ground.
B. Zink Plates and Steel Plates.
80. Zink Plates.—So far I have spoken to you of copper plates only; but etchings are also executed on zink and on steel. Zink bites rapidly, and needs only one quarter of the time necessary for copper, with the same strength of acid; or, with the same length of time, an acid of ten degrees is sufficient. The biting is coarse, and without either delicacy or depth. A zink plate prints only a small edition.[18]
81. Steel Plates.—Steel also bites with great rapidity. One part of acid to seven of water is sufficient; and the biting is accomplished, on the average, in from one to five minutes, from the faintest distance to the strongest foreground.