The DARKROOM COOKBOOK, Third Edition

Ascorbic Acid: Developing Agent or Anti-oxidant?
Patrick Gainer
Developers 29
We know it as Vitamin C, an anti-oxidant essential to human life. Photographers think
of it as a secondary developing agent in superadditive pairs such as Metol-Ascorbate or
Phenidone-Ascorbate. These have been known for years but recently made popular by
Kodak XTOL fi lm developer.
The traditional synergistic or superadditive developer solution has four active
ingredients: two developing agents, sulfi te, and an alkali. We tend to take the sulfi te for
granted for control of grain and/or pH, but don’t try leaving it out as it is also the preservative
(anti-oxidant) which keeps the developer from going fl at part way through
development. Sodium sulfi te is used as the preservative in nearly all developers, fi lm or
paper.
But a photographic developer can be made without sulfi te by substituting ascorbic
acid, using Phenidone or metol, ascorbic acid, an alkali, and water. I learned of this
quite by accident in 1993 when I ran out of sodium sulfi te. The nearest supplier was a
100 mile round trip! Knowing that ascorbic acid is an anti-oxidant and having some
in my medicine closet I decided to chance it. My escapades that day were described
in Darkroom and Creative Camera Techniques, Nov/Dec 1994 (reprinted on Ed
Buffaloes’s web site, www.unblinkingeye.com/articles, under Film and Film Developers:
Vitamin C Developers).
A simple formula to try is:
Hot water, 250.0 ml
Ascorbic Acid , 2.0 g or 1/2 tsp
Metol, 0.2 g or 1/16 tsp
Sodium Carbonate, 5.0 g or 1 tsp
Water to make 1.0 liter
Use this formula as if it were D-76 undiluted.
For photographic use it is best to purchase either ascorbic acid or its isomer
(mirror image) erythorbic acid. There are other perfectly legitimate forms of Vitamin C
that are not legitimate for photo use, such as calcium ascorbate, especially if it is to be
dissolved in propylene glycol or triethanolamine.