An avoidance of error and saving of time may be effected by making a fairly pale print and, having "fixed" it, cover the back with the scribble of a blue pencil or chalk.
We can now place this down upon the card board or paper to be drawn upon, and carefully go over everything that is to be drawn with a sharp hard point, which will leave a blue outline sketch which can then be inked in, and the blue need not be rubbed out afterwards as it will not appear in reproduction.
In the same way the original photogram can be used with a piece of blue carbon paper instead of chalking the back of the print. No attempt should be made to draw in all the details of a photogram, but only such salient points as may be required for illustration.
Another method is as follows:—Make the photogram in the ordinary way, but on "plain salted paper," or "Matt silver sensitised paper," which has been previously prepared by immersion for a short while in a solution of ammonium chlorate, 100 grains; gelatine, 10 grains; water, 10 ounces.
The photogram is to be fixed and washed, toning being unnecessary; when dry it can be drawn upon with a "fixed" or indelible black ink, carefully putting in just what parts are needed and disregarding the rest of the picture. As soon as the ink is dry, the print is immersed in a bath of mercury bichlorate and alcohol, when the photogram will gradually disappear, leaving the black ink lines on plain white paper. Nothing more is required beyond mounting on card to fit it for reproduction. Of course corrections can be made and stains, &c., be removed with Chinese white. Should it be desired to restore the bleached photogram, it can be done by immersing in a weak solution of soda hyposulphite.
The foregoing method is one given by Mr. C.G. Harper in his book "Drawing for Reproduction"; it appears, however, needlessly elaborate, and I presume mercury bichloride is intended and not bichlorate. Even with care the photographic image is sometimes slow to get rid of, and will often refuse altogether to leave the clear white blank we require.
ADVANCING TWILIGHT.
Crayon drawing on Lalanne paper; horizontal grain. (Original 10½ x 6.)