This section is from the "Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1922 " book, by Aristo Motto. Also see Amazon: Studio Light Incorporating The Aristo Eagle - The Artura Bulletin 1922 .
THE question of the correct temperature of a photographic developer is one which, unfortunately, does not get the attention it deserves but which it must have if the best results on both negatives and prints are to be obtained. In many cases, although great care is used in weighing and dissolving the necessary chemicals, success is rendered impossible by inattention to that physical factor - temperature.
A developer which is either too hot or too cold will never give results as good as those obtained with a developer of the correct temperature. For papers the developer temperature should be 70°F - for films or plates, 65°F.
If your paper developer is too cold the image appears very slowly, density is difficult to obtain, the color of the print is poor, the length of time of development is unduly prolonged in an effort to get something out and the result is unsatisfactory. In printing, the printer is tempted to increase the exposure with the idea of getting more density. This really makes matters worse. The result is similar to over exposure and development with a weak and restrained developer - bad color, absence of quality and probably granularity.
If your developer is too warm the image flashes up, density and contrast are obtained almost before you know it, the gelatine coating may be softened, the whites (of prints) may be stained, the color of prints will be too blue, suggesting lack of bromide, and the developer itself will oxidize and quickly become discolored.
At the correct temperature the best out of every print and negative is obtained. And the results are uniform and may be readily duplicated.
Portrait Film Negative, Vitava Print By Louis E. Allen Rochester; N. Y.
In some instances although the developer is warmed or cooled to normal temperature the fact that the temperature of the workroom itself is quite different is overlooked, with the result that the developer quickly adjusts itself to the surrounding conditions, which means that the negatives or prints will show all the defects of incorrect temperature.
To maintain the correct temperature is so extremely simple that there is really no excuse for omitting to do so. Stand the tray of developer on top of a second one, a size smaller, containing warm or cold water. The dish containing the developer is cooled or warmed before pouring in the developer and the temperature is thus maintained at a remarkably steady level. Use a thermometer to test and do not rely on guesswork - you can easily be 15° to 20° wrong in your estimate.