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.
Introduction. When photo post cards were first introduced they were used almost entirely for landscape, architectural, views of historical points of interest, etc., but little or no use was made of them for portraiture. The fad grew to such proportions and so rapidly it was generally conceded that it would last for but a short time. However, instead of the demand diminishing, it has grown in favor to such an extent that many professional photographers are compelled to make portraits on post cards; in fact some photographers are conducting exclusive postal photo studios.
1041. The first post cards made were sensitized by the user with solutions personally prepared. Finally solutions for sensitizing all surfaces whether post cards, heavy card-board, cloth, silk or linen were put up - ready for use - by manufacturers and may be purchased from any photo supply house.
1042. These sensitizing solutions can be applied to any surface you may desire to print on. The sensitizing, printing, toning and fixing are exactly the same as the manipulation of any printing-out paper. As the novelty and process of sensitizing materials yourself is very interesting we therefore give you the formula and methods of procedure. There may be times when there is a desire to print on special surfaces. By following instructions you will be able to prepare the material and make very satisfactory prints thereon. While these instructions apply directly to post cards, as stated above, the same methods will apply to any surface you may wish to sensitize.
Sensitizing Post Cards. For this purpose obtain a plain post card, unstamped, at any stationary store, or the officially stamped card at the post office. The next step is to prepare the cards for sensitizing. Before doing this, first apply a salting solution to the card.
. 4 ozs.
Salt (Common TableSalt)..........................
The water must be free from iron rust, as every particle of such rust will leave a black spot on the card.
1045. After the salt is fully dissolved, pour the solution into a clean 5 x 7 tray. Place the cards, one at a time, in the solution, immersing entirely and allowing them to remain about one half minute. Next pick up the cards, by a corner one at a time, and dry before a fire as rapidly as possible. Carefully avoid getting the fingers on the side of the card being sensitized.
1046. A large number of cards may be salted at one time and, when dry, stored for further use. When cards have been salted and dried, the next step is to sensitize them. Sensitize however, only as many as are wanted at the time. The sensitizing solution is prepared as follows: