When ordering chemicals for my first attempt with Pyrocat, the chap from Retrophotographic didn't stock Potassium Carbonate and persuaded me that I could use Sodium Carbonate instead. Any advice on how this might affect development/film speed kindly appreciated. I see from unblinkingeye an addendum that: "Mr. King has modified solution B to use a 100% solution of potassium carbonate instead of a 10% solution of sodium carbonate. An earlier version of the formula published on the rec.photo newsgroup called for 2.5 grams of metol in place of the phenidone. Mr. King suggests that this formulation may be more stable than the phenidone version. The keeping time for solution A when formulated with phenidone is about 3-6 months. Ted Kaufman has recommended substituting a 10% solution of sodium hydroxide for solution B." There is no more explanation than that, not we have become accustomed to on APUG! I want to keep things as simple as possible, having no desire whatsoever to reinvent wheels, just to reap the rewards of others' hard work. I do now have a digital pH meter if this is any help in adjusting dilutions etc to keep things as close to the mainstream as possible.