Cooper's Developer

[Annie M.]

I have been perusing back issues of 'Camera & Darkroom', in the October 1992 issue Mr. Anchell discusses 'Coopers Two-Solution Pyro' and indicates that it is a 'simple, effective pyro formula' and that he liked the results with this developer enough to use it for his normal processing. Cooper's is a non-metol formula.... Just wondering what role metol plays in pyro formulas.

[Jorge Gasteazoro]

Metol in conjunction with pyro produces supperaditivity, a chemical process where the result of the two developers combined is greater than that of each developer separate. It is believed that the oxidation product of one regenerates (reduces) the other one and vice versa, so that you always have "fresh" developer in the solution. This property was discovered many years ago and is the basis for many developers, most of which are hydroquinone/metol or hydroquinone/phenidone. Notable exceptions are Gainer's Vitamin C developers, which as the name implies uses Ascorbic acid to replace one of the components and the other other one of course are pyro developers which replace hydroquinone with pyro.

Given the right formulation, Hydroquinone/metol or Hydroquinone/phenidone developers are capable of producing stained negatives, but it seems that pyro is a better developer for this.

[Annie M.]

Thanks Jorge.

In Adam's book he happened to mention that metol provided good detail throughout the negative and I was wondering if eliminating the metol would effect accuance.... I was curious about the Cooper's as the formula requires fewer chemicals and less developing times. I'll try the Copper's, PMK & HD and see what I see....mind you pyro may not be suitable for me as lately I have not been chasing highlights but more concerned with the edges of light emerging in the shadows.

Cheers!

[Jorge Gasteazoro]

Acutance is mostly due to edge effects and is mostly caused by pyro, so leaving the metol away should not affect this. OTOH, you will have very slow speeds using pyro by itself. .

[Annie M.]

The film's loss could be my gain! When shooting at the beach there are often times when I actually want some exposures to go long...... never occured to me that I could gain some time from the formulation of the developer. This is great... Thanks!