There may be a problem in mixing TEA with Glycol. Pyrocat-HD mixed in glycol remains clear for years. Pyrocat-MC, mixed in glycol with a small amount of TEA, darkens appreciably after one year, and more after two years. Other than the metol/phenidone difference in the two formulas, the only other difference is the small amount of TEA in Pyrocat-MC.

The fact that you mixed the 510 Pyro 1:1 with glycol may have accelerated the reaction between the TEA and glycol.

On the other hand, I have on hand a 510 Pyro solution that is several years old. It was clear for at least two years, but now has darkened considerably. It may or may not still be good, have not tested it with film recently. But as I noted earlier re: the darkened Pyrocat-MC, the fact that it is so dark makes me very suspicious that the reason is oxidation.

Sandy King



Quote Originally Posted by Olli J View Post
Speaking about oxidation, I made recently an unexpected finding which bothers me. About three months ago I mixed 510-pyro developer, it's in TEA as you know. To reduce viscosity I mixed the ready developer with propylene glycol 1+1. Originally the solution had a pale color. After mixing the solution was divided in two parts. Within the first week I developed some films with it and they came out fine. Since then the developer has been undisturbed on the shelve in my darkroom, in well capped glass bottle, about 100ml solution in a 250 ml bottle. A couple of weeks later I noticed that the solution had begun to darken, starting from the surface and proceeding deeper. Now it's all dark but still the solution is darker on the surface than in the bottom. To me it looks like airborne oxidation, but it started much earlier than I would have expected. The other part of the developer was used by another person, who recently reported that his developer also had dark color but still functions as well as earlier, but the "life expectancy" of this developer is not very good.

I have to admit that my pyrogallol is several years old, but it still looks good, almost white, a little sticky powder. All other chemicals are fresh. Any ideas why the solution oxidized so fast? Could there be a problem in mixing TEA and glycol?

Olli