One of these tricks in illustration is a method which is largely practised for journalistic illustration in America—drawing in pen and ink upon photographs, which are afterwards bleached out, the outline drawings remaining to be processed. Although not a desirable practice from an artistic point of view, it is advantageously used for news work or upon any occasion in which expedition is essential. The photograph to be treated in this way is printed by the usual silver-print method, with the exception that the paper used is somewhat differently prepared. What is known as “plain salted paper” is used; that is to say, paper prepared without the albumen which gives to ordinary silver-prints their smooth, shiny appearance. The paper is prepared by being soaked in a solution made by the following formula:—
| Chlorate of ammonia | 100 grains. |
| Gelatine | 10" |
| Water | 10 ounces. |
The print is made and fixed without toning. It may now be drawn upon with pen and Indian ink. The ink should be perfectly black and fixed. The drawing, if it is to be worth anything artistically, must not aim at anything like the fulness of detail which the photograph possesses. An outline drawing is readily made in this way, and a considerable amount of detail may be achieved. Indeed, the temptation is always to go over the photograph in pen and ink too fully, and only draughtsmen of accomplishment can resist this almost irresistible inducement to do too much. Still, admirable results have been obtained in this way by artists who know and practise the very great virtue of reticence.
When the drawing has been finished it is immersed in a solution of bichlorate of mercury dissolved in alcohol, which removes all traces of the photograph, leaving the drawing showing uninjured upon plain white paper. Omissions from the drawing may now be supplied and corrections made, and it is now ready for being processed. If very serious omissions are noticed, the photograph may be conjured back by immersing the paper in a solution of hyposulphite of soda.
Another and readier way is to draw upon photographs printed on ferro-prussiate paper. This paper may be purchased at any good photographic materials shop, or it can be prepared by brushing a sheet of paper over with a sensitizing solution composed of the two following solutions, A and B, prepared separately and then mixed in equal volumes:—
| A |  | Citrate of iron and ammonia | 1⅞ ounces. |
| Water | 8" | ||
| B | | Ferricyanide of potassium | 1¼ " |
| Water | 8" |
The paper must be prepared thus in a dark room and quickly dried. It will remain in good condition for three or four months, and is best preserved in a calcium tube. Prints made upon ferro-prussiate paper are formed in Prussian blue, and are fixed in the simplest way, on being taken from the printing frame, by washing in cold water.
An Indian ink drawing may now be made upon this blue photographic print, and sent for process without the necessity of bleaching, because blue will not reproduce. If, on the other hand, it is desired to see the drawing as black lines upon white paper, the blue print may be bleached out in a few seconds by immersing it in a dish of water in which a small piece of what chemists call carbonate of soda (common washing soda) has been dissolved.
Outline drawings for reproduction by process may be made upon tracing-paper. Most of the rough illustrations and portrait sketches printed in the morning and evening newspapers are tracings made in this way from photographs or from other more elaborate illustrations. Although this is not at all a dignified branch of art, yet some of the little portrait heads that appear from time to time in the St. James’s Gazette, Pall Mall Gazette, and the Westminster Gazette are models of selection and due economy of line, calculated to give all the essentials of portraiture, while having due regard to the exigencies of the newspaper printing press.