Two parts Chlorate of Potash,
Ten parts Hydrochloric Acid,
Eighty-eight parts water.
Next, get an ordinary photographer’s porcelain or rubber bath or tray; lay the plate in it, pour the acid over it; in a few seconds bubbles will arise, in all the lines; brush them away with a feather; leave the plate, if there is any fine work on it, in the bath for only two or three minutes, say for a light sky; take it out with rubber finger-tips or a stick, for the acid will burn your fingers and a drop will rot your clothes, staining them light yellow; wash the plate thoroughly in clean water, dry it carefully with blotting-paper. Take some of your stopping-out varnish, thin it with a little (a very little) turpentine, paint over the very lightest parts of the drawing with a camel’s-hair brush dipped in the diluted varnish, and thus stop them out—that is, stop them from biting any more by painting them with the varnish. Wait till the places where you have painted the varnish are thoroughly dry; then put the plate in the bath again and bite the next stronger, nearer set of lines; of course, save where the lines are covered by the stopping-out varnish, they will keep on biting. Continue biting and stopping out till you get to the foreground, where the lines should now be quite broad and deep; take off the ground front and back by washing it with a rag dipped in turpentine, dry it, and the plate is ready to print from.
Another method is to commence by drawing in the darks, biting them, then drawing in the middle distance, the darks going on biting all the while, and finally the extreme distance, when the whole plate will be biting together; by this method no stopping out is necessary, but in working out of doors it is awkward to carry baths and acid around with one, otherwise one must run back to the studio, to bite between each stage. But these two methods can be mixed up, and frequently are, and you may also work in the bath, drawing lines through or over others, thus getting richness while the biting is going on. The bad fumes which are given off during the biting are not dangerous. In working with the Dutch mordant, which bites slower than nitric acid and makes no bubbles, but bites straight down, while nitric acid enlarges the lines laterally, you will inhale much of the fumes, but they won’t hurt you. Although you do not see any action with the Dutch mordant, brush the lines with a feather, else a deposit is formed and they will bite unevenly.
It is very difficult to tell when a plate is well bitten, the biting is very difficult, but on taking it out of the bath and holding it on a level with your eye, you can see the bitten lines; you can also feel the biting with a needle, and you may take off a bit of the varnish with your thumb-nail or turpentine and look at the lines, re-covering them again with the stopping-out varnish; but after this, of course, they will not bite in that place.
Again, the lines do not bite evenly; where they are close together they bite faster, and, after the plate has been in the acid some time, it may change its speed of biting; differences of atmosphere and temperature affect it even with the same acid on the same day; if the nitric acid is too weak add more acid; if too strong pour in water, and quick, else the ground will come off: it is too strong when it boils and bubbles all over; it is too weak when there are no bubbles. Dutch mordant eats always slowly, and never, so far as I know, destroys the ground. At the last, for very strong darks, you may sometimes use a little pure nitric acid, but it will most likely tear up the ground, and if you leave it long enough will spoil all your lines, giving you only a great black hole. These are the systems employed by all etchers; the lengthy dissertations about white ground, silver ground, positive and negative processes, need not concern you, they are never practised, and mostly unknown to the best men. These simple directions should enable you to produce artistic plates, if you have the necessary ability. Still, when you have had a proof of your plate pulled—I will talk of printing in the next lecture—you will find that there are all sorts of imperfections in it, possibly holes, places where it is not bitten enough or too much bitten, or that it is too dark or too light all over; it is but seldom that a plate is right when the first proof is pulled. If you find a hole bitten in it, take a burnishing tool, flatten the hole down as much as possible, find the place on the back with a pair of calipers, hammer it up from the back, placing it on an anvil, burnish it again and polish the surface with charcoal, oil, and rags; revarnish the place, redraw, and rebite it. If it is only a small place you may take up some nitric acid on a feather, and paint the little spot to be rebitten with that. A few drops of the acid have nearly as much power as a great deal. In fact you may paint the face of your plate with acid and do your biting in that way, without ever immersing it in the bath at all. If it is too much bitten it must be rubbed down with charcoal and oil, a tedious process. If it is too light it must be rebitten all over; then take a rebiting roller, putting some liquid etching ground on a separate plate, take the ground up on the roller and roll the face of the plate very carefully; the ground should cover the face without going into any of the lines; heat it very slightly to dry the ground, leave it for a day or so and then bite as before. If there are places where lines want joining or little touches of dark would be effective, put them in with a graver or a point.
You may use a graver altogether, and produce a line engraving; or a point, either steel or diamond, and make what is known as a dry-point etching, that is, merely a scratched drawing on the copper; the point throws up, as you draw with it, a furrow, which is greater or less as you incline the point, and this holds the ink, and is called burr, and gives for a few proofs great richness; a steel face can, however, be put on the copper plate, and any number of pulls may be taken. The difference between the cutting of lines with a graver and the drawing of them with a point is this: the graver, both in metal and wood, is pushed from one; the point in etching, and even the knives in wood cutting, are drawn toward one.
Messrs. Roberson have invented a plate of celluloid which, for dry point work, seems to be fairly good, and as this plate is white or cream-coloured, as one draws on it the lines may be filled up with paint, and one may thus see the drawing as one works. Of course, the same thing may be done with dry point on copper. The great advantage of the celluloid is its lightness. It must not, however, be heated in printing, otherwise it will be ruined. Many etchers are now making experiments with aluminium, but no certain results have as yet been obtained.
There are many other forms of engraving included under the title of Etching, although, properly speaking, they have nothing to do with it.
Aquatint: a ground, made by depositing powdered resin in solution with spirits of wine, is poured on the plate, slightly heated, and as it dries the resin adheres to the plate and cracks up irregularly; a drawing may be made on this, and stopped out in the usual way. Or powdered resin may be sprinkled on the plate, heated, when it will adhere, or the plate may be placed in a box containing resin in very fine powder, heated, and the box shaken; the resin will settle on it and produce the ground.
A very similar ground may be made by passing the ordinarily-grounded plate through a copper-plate printing-press, with a piece of sandpaper over it, three or four times, then the design may be painted on it in stopping-out varnish, and at times a very good result may be obtained. Lines may be put in, etched before the ground is laid; but personally I don’t like the lines at all; without them the result is rather like a bitten painting. Silk and canvas can also be placed on the grounded plate, which is then run through the press, to get tints in the ground.