After development is complete the bichromate salt is discharged, and the image rendered perfectly insoluble by well washing in cold water and placing in a dish containing a 5 per cent. solution of potash alum, after which it is again washed and dried.
Another method of making a transparency and one that involves less trouble is by means of the transparency plates which are now in the market. Of these we have tried Carbutt's with the greatest success. For these the following instructions are given:
The requisites are, a deep printing-frame a size larger than the negative to be used, with a flat glass bottom clear and free from scratches (crystal plate is best), a dark-room Lantern, or other artificial light, and Keystone Gelatino-Albumen Plates. Transparencies can be made same size of negative by contact and exposure to artificial light, or enlarged or reduced in the camera by daylight, with equal perfection in result. To make transparencies by contact place one of the Keystone thin crystal glass transparency plates over the negative in printing-frame, lay piece of dark soft material over it, close down the back, and expose to the light of the lantern or to a gas flame or other artificial light, for 10 to 30 seconds, according to density of negative, at a distance of 20 inches from the flame. Use the following developer:
600 c.c.m Distilled Water 20 ounces 120 grammes Sulphite of Soda Crystals 4 ounces 22 grammes Eikonogen 330 grains 10½ grammes Hydrochinon 160 grains 960 c.c.m Water to make up to 32 ounces
600 c.c.m Distilled Water 20 ounces 60 grammes Carbonate of Potash 2 ounces 60 grammes Carbonate Soda Crystals 2 ounces 960 c.c.m Water to make up to 32 ounces
For use take 1 ounce (30 c.c.) of A, 3/4 ounce (25 c.c.) of B, with 4 ounces (120 c.c.) of water.
More of A will increase density, more of B will increase detail and softness. Temperature of developer should not vary much below 65 deg. nor above 75 deg. The after treatment is same as with any other developer.
Let the development continue until the blacks look quite strong, and detail showing in the high-lights; wash off developer, then immerse in
CARBUTT'S NEW ACID FIXING AND CLEARING BATH.
4 c.c.m Sulphuric Acid 1 drachm 480 grammes Hyposulphite of Soda 16 ounces 60 grammes Sulphite of Soda 2 ounces 30 grammes [D]Chrome Alum 1 ounce 1920 c.c.m Warm Water 64 ounces