Average Bitings.

42 deg., No. 15 minutes
37 deg., No. 25 minutes
33 deg., No. 32 minutes
30 deg., No. 42 minutes
Temperature of bath at 70 deg. Fahr., with No. 103 tissue.

Total of different bitings, from 10 to 25 minutes, according to depth of printing. It always varies. There is no hard and fast rule; you must in time learn to judge by your eye alone. The acid will first attack the thinnest part of the film, wherever that may be, and when the darkening of the copper ceases to spread to the next thickest parts, instantly pour off the acid, and pour on the 37 deg. Do not allow the atmosphere to act on the gelatine while biting any longer than is necessary to pour off one bath and quickly pour on a new one. The 37 and 33 deg. baths are for the middle tones, the 30 deg. for the most delicate ones. The action of each bath is cumulative, the 37 deg. biting a little where the 42 deg. had bitten, the 33 deg. doing the same for those before it, besides taking care of itself, and the 30 deg. attacking all more or less. During the biting with the 30 deg. solution, it should be continued until the whites just turn color, and a minute beyond; that is, the copper should begin to show a very little under the thickest and darkest film.

(Note that in the carbon resist the shadows are transparent and the high lights are opaque.)

The length of the last biting very seldom is over two minutes. It is better to overbite your darks, and underbite your lights, if you vary any.

The amount of moisture in the air and the heat of the day influences the length of biting. In hot weather in summer it is very difficult to work the process, the walling wax being discarded and the copper (back and edges protected by varnish) placed in a porcelain tray, surrounded by ice-water and kept at 65 to 70 deg., and the acid pured over the plate to the depth of one inch.

CHAPTER VII.

Cleaning and Polishing the Plate, with Tools Necessary for Retouching.

When the biting is finished rapidly place the plate under the tap and rinse thoroughly, breaking away the film with your fingers; it seems to have rotted under the action of the acid and is easily removed.

Remove the walling wax, clean off the varnish with chloroform or turpentine, or alcohol first, and chloroform last. This leaves a dim picture on the plate, with a kind of scum over it; wet the plate with turpentine and start heavily with rouge, rubbing to and fro equally all over the plate with a ball of absorbent cotton; continue this treatment, using less and less rouge and more turpentine until you give the final polish to the high lights with a clean dry piece of cotton. Be very careful not to overdo in rouging; the scum (if the biting of the plate is of medium strength) should clear from the plate with hardly a touch, and with very little rouging. Some plates require a great deal of rouging; it then generally means that you must look to your sensitizer. I again draw your attention to the rouging; here is where any artistic feeling you may possess will come into play with taste and patience.

After the plate is rouged sufficiently, an engraver's burnisher is used to clean up the highest lights and to modify others. Two or three roulettes of different fineness are valuable to touch up any darks that need deepening; it matches very well with the grain, but I am always trying to dispense with the use of the roulettes; one ought to get it with the acid alone. A No. 6 sewing needle in a holder (dentist's pin-holder, screw end) is necessary to touch out occasional white specks. You will have plenty of them at first unless you look out carefully for dust on the film; keep all your solutions constantly attended to by occasional filtering, and don't use your sensitizing solution more than half a dozen times; keep it well corked; if it gets old it scums the plate too much.

CHAPTER VIII.

Printing the Plate and Steel Facing.

Before final finishing by hand a working proof should be printed from the plate by an expert plate printer, by which, what the plate needs can be determined before final proving.

Have the plate proved on different papers, and with different colored inks, so as to judge the effect. Imperial Japan is the best paper, besides etching paper, India, thin Chinese and Japanese papers. The cost of proving per single proof is 25 cents for a 4 × 6 plate on Imp. Japan, about $2.00 per doz. same paper; etching paper, about $5.00 per 100—less for large quantities.

A second-hand D press, suitable for printing large or small editions or for proving, can be bought in Boston or New York for from $75 to $100. For instructions in printing see Hamerton's "Etchers and Etching."