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BORAX DEVELOPER CHARACTERISTICS
H. W. Moyse and D. R. White*
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rT^HIS study of borax developers was undertaken because their I wide use emphasized the importance of detailed knowledge of -*" their action. The results of the study not only permit the selection of a developer formula which seems very satisfactory, but also points out the sort of variations that will either increase or decrease the activity of the developer, to meet any special needs that may occur. The tests were made with a number of negative materials in each development. Strips of film were exposed back of a sector wheel which gave a series of exposures varying on a time scale with factor two steps between successive areas of the strip. Strips were then developed for a number of lengths of time in the developer being tested. During this development the flat developing tray used was rocked systematically to give high, reproducible agitation which rapidly removed development products from the emulsion surfaces of the strips which were held flat at the bottom of the tray. The densities were read as diffuse densities and gave the density-time of exposure-time of development data used in comparing the developers. To cover systematically the range of possible combinations of chemicals two series of tests were conducted. In each series one basic formula was being considered, and the test centered to some extent on that formula but in both series the variations covered a relatively wide range of concentrations. Many of these, of course, were such that they all aided in showing the relationships among and the developing effects of the constituents. Table 1 gives the two basic formulas and also indicates the range of concentrations tested.
Table 1
Chemical Series 1 Series 2 Range
Sodium sulfite (Anhyd.) 100 g. 85 g. 1-200-g
Borax 2 5 O-Saturation
Metol .. 2 2.5 1-10
Hydroquinone 5 0 0-20
Potassium Bromide 0 0 0-2.5
Water to 1 liter 1 liter
Results Sulfite
It was found that an increased rate of development accompanied increases in sulfite content up to a rather definite maximum, beyond which additional sulfite caused a falling off in high densities and in many cases a distinct loss in effective emulsion speed. Fig. 1 shows curves for one time of development in developers differing only in sulfite content.
The increasing development occasioned by increase of sulfite concentration from the initial low value is apparently due to the increased alkalinity produced by the larger quantities of sulfite. The
* Research Laboratories Dupont-Pathe Film Mfg. Corp.
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