PQ Developer of long, even infinite, life.
The developer worked out to produce negatives of the type required by photofinishers and to have a long, even indefinite, life is marketed by Ilford Limited under the name- “Autophen”. Extensive trials in the laboratory and under practical photofinishing conditions show that it fulfils the requirements very well. Variations in characteristics of the developed image in one of the field trials are shown graphically. A 24-gallon tank was used and a total of 65,000 rolls was put through with topping-up replenishment using the replenisher designed for this purpose. Periodic spectrometric tests indicated that over the relevant period corresponding to over 2000 rolls per gallon of fresh developer the relative speed (at a density of 0.l above fog) varied by about ½ stop, tending to level out at approximately the same value as that of the fresh developer. Contrast, measured by an average gradient over a 1.5 log E range, tended to stabilise a little below its initial value, the range being from 0.67 to 0.78 with an initial value of 0.75. Fog was likewise closely controlled. The tests therefore showed that an equilibrium developer condition could be established which was very close to the condition of the original solution, and the question of the ultimate life of the developer then hinged on considerations other ` than the maintenance of photographic quality. The practical limit is usually set by the accumulation of sludge and dirt in the developing tank. During a season’s work this should not be troublesome, but over two or more years may affect the negatives produced.
B.J., 1957, June 14, p. 342.
Ilford's research dispels the myth of Phenidone not keeping well in solution.
Ian