Quote Originally Posted by Ian Grant View Post
The hike in pH seems to be mainly so Agfa could get more activity out of less developing agent cutting the cost of manufacture. This was what Edward Zimmermann and other photographers mainly German where complaining about in the past and why some prefer Calbe R09.

In Europe, (less so in the UK) Rodinal has always been main stream developer, it was one of Agfa's main film developers, I've no idea how it sold in proportion to others.

Are you saying that Ascorbic at pH 11 is the cause of the fogging ? Or is this not due to the fact that a high sulphite level's required as an anti-oxidant ?

Ian
I didn't use any sulphite in my Q&D trial. I did, however, try the same amounts of p-aminophenol and ascorbic acid with KOH as alkali. Total disaster. Very dense fog. pH was much higher than with carbonate. I attribute that to the fact that although the same number of K molecules is used in each case to form the aminophenolate, a little extra carbonate does not have the same effect on pH as a little extra KOH. The ascorbic acid becomes the nearly neutral ascorbate in both cases. Thus, the pH is practically all due to the potassium aminophenolate when carbonate is used.

If ascorbic acid behaves with p-aminophenol as it is theorized to do with Metol, it will regenerate oxidized aminophenolate. By keeping the pH below the point where ascorbate is a developing agent, I should be able to increase the relative amount so as to extend the storage life of a stock solution greatly. If it is successful, it will probably be a great disappointment.