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( Originally Published 1917 )
If the plate has stood for some time after being drawn upon, it may be necessary to wash the ground in a solution of acetic acid and salt in order that the acid may bite more evenly. To a half cupful of acetic acid, of about the strength of ordinary vinegar, add two teaspoonfuls of common salt. To remove any grease that may be on the ground, brush with a piece of cotton dipped in alcohol before putting in the bath. Cover over the sides and back of the plate with an acid-resisting varnish. If nitric acid is to be used, pour it into a porcelain dish to a depth of about one inch and put the plate in, first having water handy to wash off the plate and also any acid from the fingers. The old way to make the dish for the acid was to your fingers if you wash your fingers at once, or you can use a piece of wood, with a chiselled end to press under the edge of the plate for a lifter. Grease on the fingers will protect them from the acid.
If anything, over-bite the distance because it is easier to reduce than to deepen shallow lines. It is wise to wear a blouse, similar to the workman's blouse in France, which will entirely cover your clothes, as the acid has a most mysterious way of making bright spots on clothing, no matter how careful you are. It is best not to try to finish a plate in the first biting. Get the essential parts. Leave the large light, etc., for future biting which you can do so much better with a proof of the work before you. Increasing the temperature of the acid increases speed but decreases the variety. Nitric acid bites quicker on a warm damp day. S-trong acid tends to roughen and foul the plate. An old saying of etchers is, "One day of stopping-out is worth five with the needle."
OTHER METHODS OF USING ACID
Etching in the bath.-Place the grounded plate in the acid bath and begin by drawing those lines which are to bite the deepest and work toward the lightest. It is a most diffi cult way for a beginner to etch. I would not advise trying it until you have had a good deal of experience with the stopping-out. Of course you will use this method some in the stopping-out process. Use an old needle or a sewing needle in a wooden handle because the acid will eat the needle as well as the copper. However, it will last for some time. This method was invented by Sir Seymour Haden, but is not used by many etchers. It has too many difficulties.
Avoiding stopping-out.-In this method first draw in only the parts that are to be bitten the most. Place the plate in acid until these lines are bitten enough, and, on removing it, wash in water and draw in the set of lines that are the next grade lighter than the first, and so on to the lightest. Of course at any time between bitings you can remove the ground in order to make a print which will be a guide in further work. One of the advantages of this way of working is that you can run lines across those already bitten. For instance, the lines of a sky showing through foliage would require a lot of careful stopping-out in the old method.
Still another method is to place the plate on an inverted dish in the bottom of the empty tray, pour the acid on the plate and manipulate it with a feather. The acid will stay where wanted if mixed with a little saliva. This method is not as nice as it is useful. Start the acid where you want the darkest lines and enlarge the space covered by the acid with the feather until you have the faintest lines bitten.
Whistler's method of biting a plate as described by Otto Bacher is as follows: "He put the plate ready for biting on the corner of the table, then poured the acid slowly onto a feather held against the mouth of the bottle, the acid dripping from the end of the feather. By moving the bottle and feather back and forth he covered the plate entirely with acid. The feather was employed to keep the plate equally covered. When the biting was finished he would place the feather against the tilted edge of the plate and drain the acid back into the bottle." If you employ this method it would be wise to have plenty of water near in case of accident.
Hamerton's Positive Process.-This is a method of working in black on a white ground. The ground is made white instead of black and the Dutch bath is used, thus giving a white surface and black lines. I doubt if this method is much used because in practise one soon becomes accustomed to the golden lines of the copper on the black ground. This process, and the one following are fully explained in Hamerton's Etcher's Handbook. Bracquemond drew with pen and ink on a clean copper plate. He then ground the plate in the usual way and immediately immersed it in water-the ink softens in the water and in a quarter of an hour the ground will come up where the ink lines are if rubbed with a flannel. Bite as usual and the result resembles a pen and ink drawing. Flour of sulphur and oil put onto a plate with a brush for five or ten minutes gives a flat tone. The sulphur makes the plate look darker than it prints.
In practise, the etcher usually employs a combination of several or all of the above methods. A good general rule in biting is to err, if at all, in over-biting the distance and under-biting the foreground.
Should the ground be improperly laid the acid may find its way through in spots and show what is known as foul biting. Some of this fouling may come where it can remain with advantage, but should any of it come in the delicate parts such as the sky, it must be removed. Gouge it out first with a scorper, a tool something like a burin, knock the plate up from the back and polish. This is tedious work, and if your plate is covered with a deep fouling you may find it easier to do a new plate.
Sometimes fouling is purposely done. If there is not much wanted, a simple way is to take a coarse needle and tap or dot the ground on the plate wherever you want the fouling. Another method is to lay a dusty ground. Work in a cool bath until the parts to be kept clear are finished. Paint these out and warm up the bath when the dust spots will probably foul all you want. Or warm the plate and touch ground with a fluffy rag where you want fouling. Put sandpaper on the ground and rub on with burnisher. This can also be done on the plate after the ground is removed, using more pressure with burnisher.
Warm up the ground and sprinkle with a little salt. Wash off the salt and bite. Fouling will show wherever the salt has touched the ground.