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.
Controlling The Developer For Prints And Plates. Full control of contrast is secured by varying the dilution of the developer. Always bear in mind that the stronger the developer the softer the prints. When printing from a thin negative always dilute your developer, as this will enable you to produce more contrast. Remember that this rule is reversed when developing plates, as strong developers develop quicker, stronger and more contrasty, while diluted developers give softness.
Plate Developing. Always bear in mind that the speed of development of the plate is entirely controlled by the amount of dilution of the developer. The more water you use the slower the plate will develop. The time of development can be made very short by using a full strength developer. Great care, however, must be exercised that exposures are even; in fact it is necessary that the plates should be fully timed, never under-exposed.
Making Post-Cards for Quick Delivery. 391 up according to the formulae given by the manufacturers of plates, can also be used. After a plate has been fixed, rinse for a few moments in fresh water and then place in the following solution: Formalin, (or 40% formaldehyde), one part to ten parts water. The formalin or 40% formaldehyde, can be purchased at any drug store.
796. Allow the plate to remain in this solution for a few seconds. Remove and again carefully rinse for a few moments, and then place in a bath of wood alcohol, diluting the wood alcohol about one-half with water. Allow the plate to remain for a few moments in this and then set up to drain. The alcohol which is left on the surface of the negative will slightly attack the celluloid which is placed over the wet negative, so that this covering which adheres to the face of the negative will make the latter waterproof.
Printing From Wet Negatives. After the plate has been drained for a few minutes, place on the emulsion side a piece of thin transparent celluloid. The celluloid can be obtained from any film manufacturer or through your dealer.
798. Having treated the negative as above, now place it in a printing-frame of sufficient size to permit the shifting of the negative, cut-out and card, so that the portion of the negative desired can be printed on the postal. Print in the ordinary way, just the same as if the negative was dry. After the order has been printed from the negative, put it back in the washing tank for regular washing; then place in a rack to dry, after which file for duplicate orders. The post-cards are developed and fixed in the usual manner.
Printing Light. Although there is very little danger of melting the film of the wet negative when treated with the formalin bath, yet it is advisable to take some precaution. Electric light is the most satisfactory illumi-nant, as it gives off a minimum amount of heat, and, as it is generally available, we recommend its use.