Early Work In Photography
A Text-book For Beginners

92 Early Work in Photography. A negative is sometimes so extremely thin and ghostly as to render anything but the most drastic treatment un- availing; in such cases (and in those only) we recommend the use of uranium, which changes the color of the deposit to red, and effectually stops the passage of light. Do not use it on a negative- requiring but slight increase of density, otherwise it will yield nothing better than “soot and white- wash” prints.. The following is the formula: Uranium Intensifier. Uranium nitrate ... ... ... io grains Potassium ferricyanide ... ... io „ Water ... ... ... ... io ounces When dissolved add— Glacial Acetic acid ... ... 4 drams This intensifier must be used as soon as mixed, as it will not keep. It is a good plan to keep the uranium nitrate in a solution of a known strength, say 80 grains per ounce. The well washed negative must be immersed in the solu- tion and rocked until it acquires the desired color; it changes rapidly from black to chocolate brown, and then on to red. The clear parts of the negative become yellow in this bath, but a few minutes washing under a “rose” jet will remove the stain, and the negatives may then be dried. The color leaves the negatives entirely if washing be prolonged, and a flow of water on one particular part of the negative re- moves the intensification from the place, so care must be observed to wasli evenly and just enough to clear the yellow- ness from the shadows. Very dense negatives are often caused by over develop- ment, and they are frequently so dense as to require several days’ exposure to sunlight, to obtain a print. This is a fault that is easily remedied as follows: Dissolve about thirty grains of potassium ferricyanide (red prussiate of potash) in an ounce of water, and add it to three ounces of fresh hypo fixing bath of usual strength; this forms the reducer. If the negative is dry, it must be well soaked in water, or in the fixing bath, and then put in a white tray and covered with the reducing solution. Ilie disli must be rocked to prevent uneven action, and it must be borne in mind that this solution acts with great rapidity ; examine the plate frequently, and, when nearly thin enough, remove it to a tray of clean water and wasli it thoroughly. Thus it is