DARKROOMS AND DARKROOM PRACTICE 



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consistent scheme of switching should be employed, e.g., snap switches for safe lights, 

 push switches for general illumination. Then in the dark, there is little chance of 

 turning on the wrong lights. A still safer system is to make it necessary to insert a 

 key into the switch that controls the general illumination; but the trouble with this 

 is that the key may be lost, unless it is permanently attached to the switch in some 

 manner. A foot switch controlling a light used for inspecting a print, frees both 

 hands for rocking a tray, etc.. 



Special paints are available for darkroom use. For use on trays, benches, sinks, 

 etc., these paints should be acid and alkali resistant, and light in color. Kodacoat of 

 Eastman Kodak, Larkaloid of Larkin Co., Tornesite of May Products Co., and Pliolite 

 of Pratt and Lambert are recommended. It seems to be extremely difficult to get a 

 paint which certain developing agents will not stain, but frequent painting will assure 

 that benches, etc., are kept clean and in good condition. 



Ceilings and the upper parts of the walls may be painted with a light buff or 

 green. Equipped with an indirect illumination scheme, the light-colored ceiling will 

 contribute to general illumination which will be much better than that secured by 

 directly illuminating the object to be inspected bj^ rays from the safe light. Lower 

 parts of walls, likely to be touched with wet hands, may be painted a darker color and 

 with a paint which may be more stain resistant. 



Ventilation. — It is highly important that those who work in a processing room be 

 provided with a copious supply of fresh air and that stale and noxious air be constantly 

 withdrawn from the room. Since the room must be abso- 

 lutely dark at times, this ventilation problem is serious in 

 the small darkroom, although the commercial establishments 

 have the funds and facilities for doing a thorough job of 

 ventilation. If a vent is cut at the top and at the bottom of 

 the walls of the darkroom and if these vents are properly light- 

 trapped, a circulation of air will take place, the warmer air at 

 the top leaving through the upper vent, and the cooler air 

 coming in at the bottom. If sufficient circulation does not 

 take place naturally, a fan may be installed to force air out 

 of the room. 



Eastman Kodak Co. and others provide simple blowers 

 which may be installed in the wall and which provide a con- 

 stant and sufficient change of air for darkrooms of various 

 sizes. Clerc cites a French law requiring 10 cu. meters of fresh 

 air for each person working in the laboratory, the air to be 

 completelj' changed at reasonable intervals. 



Temperature and Humidity. — The darkroom should be maintained at a tempera- 

 ture of 65 to 70°. The latter is a comfortable working temperature, and anj' tempera- 

 ture within this range is satisfactorj^ for processing of all kinds. It is difficult, however, 

 to maintain a darkroom at a constant and desirable temperature without special 

 efforts, which are usually beyond the means of any but the larger establishments. 

 If the darkroom temperature is outside the range 65 to 70°, the photographer is dis- 

 tinctly handicapped in doing consistently good work because he must engage in a 

 constant struggle to maintain his solutions above or below the ambient temperature. 

 Developers for paper prints should not vary much from 70° for best results; films and 

 plates will develop to different contrasts unless the temperature (and strength) of the 

 developer is always the same. This is particularly important to the worker in color 

 photography who is faced with the problem of making three negatives with exactlj^ 

 the same contrast: virtually an impossible task if the developer cools or heats up dur- 

 ing the development period. 



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2. — Light-trapped 

 ventilator. 



