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Fine-Grain Developers — Carlton and Crahtree 4^1
a solution which is so near the saturation point with resj^ect to these chemicals that it is not of practical interest.
The Elon content alone can be doubled but this produces no appreciable increase in the rate of development because the effect of the Elon is offset by the decrease in alkalinity (Nos. 1 and 8, Table II). The effect that can be produced by an increase in the borax content will be discussed under ' ' alkalinity. ' '
When Elon is used without hj^droquinone with two grams of borax per liter the concentration can be increased to 16 grams per liter. An increase above 4 grams per liter produces very little increase in the rate of development because very little of this is converted to the Elon base which is the active form. If borax is added to convert the Elon into the Elon base, the rate of development increases with the Elon concentration. The gamma produced for a constant time of development increases as a linear function of the logarithm of the Elon concentration.
If the Elon is omitted, the hydroquinone concentration can be increased to 15 grams per liter, but the resulting developer has very little developing power. A fair rate of development can be obtained with 10 grams of hydroquinine in the absence of Elon if the borax content is increased to 20 grams per liter (No. 21, Table
II).
The quantity of Elon and hydroquinone can be reduced to decrease effectively the rate of development. If the quantity of borax is also reduced to 50 per cent (see No. 23, Table II), a developer with the following formula is obtained which gives a still greater decrease in the rate of development.
Metric
Avoirdupois
Elon
1.0 gram
1.0 lb.
Hydroquinone
2.5 grams
2.4 lbs.
Sodium sulfite (anhydrous)
100.0 grams
100 lbs.
Borax
1.0 gram
1 lb.
Water to make
1.0 liter
120 gal.
A comparison of the time-gamma curves for this developer (B) and the regular borax developer (A) is given in Fig. 3. This developer can be used very effectively for machine development when the construction of the machine demands a developer that is slower than the regular formula and when fresh developer can be added sufficiently fast to compensate for the depletion of the developing agents.