This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Copying Old Pictures. Should you have engravings or rough prints, or old albumen prints badly scratched and cracked, you can greatly improve them by coating the print with glycerine and then squeegeeing on to a good, clean glass. The glass containing the print can be fastened to the copying board and, in order to avoid reflection from the glass into the lens, attach two large sheets of tissue paper together and lay them across the two wire rods extending from the copying board. The tissue paper will screen the light and give even illumination over the picture, besides overcoming any reflection of the lens. In fact, it is a good idea when copying anything with a glossy surface to shield the original with the tissue paper. Especially should this be done if the reflection bothers you at all. See Illustration No. 1, page 154.
Placing Originals To Be Copied In A Printing-Frame. Where prints are bent and warped, a good way would be to place a sheet of plain glass in a printing-frame larger than the print to be copied, then lay the print next to the glass and clamp the back of the frame in position. Attach the printing-frame to the copying board and copy the print through the glass. It is needless to state that this glass must be perfectly clean and clear from any spots or marks. The glass over the print often assists in giving detail, as well, to old prints. For pictures that are yellow from age, perhaps soiled from handling, the surface may be cleaned by rubbing over with some stale bread. The bread usually will take up the smoke and soil from the print, and it will make a much better copy. When copying old pictures that have been stained, you should stop down only enough to make them clear and sharp. Should you stop down to the extreme you would accentuate these spots and stains, and they would appear stronger in the reproduction. Understand, your focus must be sharp, but not wiry, for this class of work, and do not be afraid to give long exposure. Any copy must be fully timed and never underexposed, but particularly those you stop down must be timed more fully; also remember that it is best to use slow plates for all copies.
Copying Originals That Are Flat In The Half- Tones. Such originals may be improved in the copying by giving a quite accurate exposure and using a restrained developer. In place of four or five drops of Bromide use about ten. Pyro developer is the best for such reproductions.
Copying Contrasty Pictures. Contrasty pictures can be improved in the copying, by giving full time and developing, with normal developer, to a good strength.
Copying Line Drawings. When copying line drawings care must be exercised lest you produce distortion. See that the camera is perfectly level, and the ground-glass perfectly perpendicular and on exact alignment with the drawing. Usually these drawings are quite large, and therefore a short focus lens should be used. To insure accuracy, the drawing should be measured on the ground-glass, and should the lines converge in any direction, by means of the swing-back you can adjust them so they will be reproduced true to the drawing. A very small stop must be used for this work, as this will accentuate the contrast, as well as give good sharpness, which is essential in this instance; and negatives of drawings must be developed in contrasty developer.