CHAPTER III.
BITING.
27. Bordering the Plate.—This work took some time. Our young student, impatient to see the transformation wrought by the acid, came back without keeping me waiting for him.
“Hurry up! A tray, acid, and all the accessories!”
Instead of using a tray, I tell him, we can avail ourselves of another method, which is used by many engravers, and which consists in bordering the plate with wax. This wax,[6] having been softened in warm water, is flattened out into long strips, and is fastened hermetically and vertically around the edges of the plate, so that, when hardened, it forms the walls of a vessel, the bottom of which is represented by the design drawn with the point. To avoid dangerous leaks, heat a key, and pass it along the wax where it adheres to the plate; the wax melts, and, on rehardening, offers all possible guarantees of solidity. We now pour the acid on the plate thus converted into a tray, and as we have taken care to form a lip in one of the angles made by the bordering wax, it is an easy matter to pour off the liquid after each biting. This proceeding is useful in the case of plates which are too large for the tray. Otherwise, however, I prefer a tray made of gutta-percha or porcelain.
28. The Tray.—Let us now install ourselves at this table, and let us cover the margin and the back of the plate with a thick coat of stopping-out varnish. As soon as the varnish is perfectly dry, we place the plate into the tray standing horizontally on the table, and pour on acid enough to cover it to the height of about a centimetre. This depth, which is sufficient for biting, allows the eye to follow the process in its various stages.
29. Strength of the Acid.—This acid is fresh, and has not yet been used; bought at forty degrees, I mix it with an equal quantity of water, which reduces it to twenty degrees. This is the strength generally adopted for ordinary biting. Its color is clear, and slightly yellow; but as soon as it takes up the copper it becomes blue, and then green. As, in its present state, it would act too impetuously, I add to it a small quantity of acid which has been used before. You may also throw a few scraps of copper into it the day before using it; the old etchers used for this purpose a copper coin, larger or smaller, according to the volume of the bath.[7]
30. Label your Bottles!—One day, one of my pupils, having a bad cold, did not notice the difference between the smell of the acid and that of the turpentine, and so plunged a plate which he desired to bite, into a bath of the latter fluid. “It's queer,” he said, “this won't bite, and yet the varnish scales off.... The lines keep enlarging, and run into one another! What does this curious medley mean, which appears on the plate?” It was simple enough. The spirits of turpentine had dissolved the ground, and consequently the plate developed a shining and radiating surface before the eyes of our wondering student, as if it had just left the hands of the plate-maker.
Advice to those who are absent-minded, and who are liable to mistake fluids which look alike for one another,—Label your bottles!
31. The First Biting.—Let us make haste now, I say to my pupil, to do our biting. As the heat of the day abates, the acid becomes less active; and besides, to judge by the delicate character of the original we are to render, we shall need at least two or three hours, all told, for this operation. The task before us consists in the reproduction of a given work, the merit of which lies in the gradation in the various distances. It needs time and attention to be able to carry all the necessary processes successfully into practice.