Pyrogallol

[Olympusman]

Thew wikipedfia article PYROGALLOL gives a pretty fair overview of Pyrogallic Acid in photography. "Pyro" developers were very popular up until the 1920s. Because of its propensity for oxidation, many Pyro formulas are two part (A and B) with the alklai in part B and the two parts mixed before use. Because of its staining properties it produced a very silky negative. Some formulations were used in "stand" developers in which sheet film was hung in hangers and lowered into a hard rubber deep tank and left to steep in the developer with no agitation until the development was exhausted. The result was that the highlights in the film would exhaust their share of the developer first and the shadows would continue to use their share, resulting in a broad contrast range. Of course, those negatives would be pretty much bulletproof, but the softer contrast papers at that time were able to handle the density. I worked on a bookproject for the National Park Service for the 100th anniversary of Sequoia National Park in which I had to work with 100 years worth of negatives. Some of those pyro negatives meant very long exposures and up to three minutes in a tray of Dektol with no agitation.