By: Gordon Hutchings
I recently noticed a white precipitate in Solution 'A' of my PMK developer, which is now several years old. I have also noticed a progressive increase in fog in negatives (FP4+) processed in this chemistry.
Is it possible that the precipitate is sodium sulphite and that this is causing the increase in fog density, due to loss of acidity and hence an increase in pH?
Clearly something has gone wrong with the A solution. Don't use it. In over 30 years use, I have never seen a white ppt. in the A solution. My guess is that somehow the bi-sulfite has combined with something to cause it to become an insoluble carbonate compound, I think. If this happens, the pH would be out of control and fogging and oxidation would occur.
Time to buy some new solution.