Quote Originally Posted by Photo Engineer View Post

I say again that the adjustment in formulas may have been to track the changes in average emulsions from Agfa, Kodak and Ilford as they had much more surface iodide. This would entail some change in pH and bromide to tweak development and other paramaters.

I agree, and suspect that the big change with the addition of anti-foggants came with the emergence of 35mm film which happened much faster growth-wise in the German market, with the rest of Europe lagging slightly behind and even slower take up in the US.

But remember that Calbe RO9 is much lower pH and not much more than a 30% Potassium Sulphite solution would be. So really the pH change came in 1964.