[Leica] Free: unopened packets of Xtol

[freakscene at weirdness.com (Marty Deveney)]

Hi Mark,

I wasn't suggesting you'd said to add ascorbate to Rodinal, but Rodinal is 
not alone in having a high pH.  Many MQ and PQ formulae have a high 
(alkaline) enough pH to cause infectious development - D76 is among the 
exceptions.  Tests I've conducted and am still conducting indicate that a 
key to Xtol's success lies as much in its moderate (Kodak says 'weakly 
alkaline') pH as the use of ascorbate.  In this sense the thing that is 
great about ascorbate is that it can function as a developing agent and 
preservative at this moderate pH, where other agents cannot function.  

I am trying to encourage rigor in testing - adding ascorbic acid to 
pre-mixed D76 did nothing in my tests except make the development times 
somewhat longer to achieve the same CI; this can help prevent 
over-development, a problem that seems to manifest often and at the 
encouragement of film manufacturers, but I measured no statistically 
detectable change in grain size or acutance when adding ascorbate to 
existing MQ or PQ developers.  Mixing up your own E76 is different; that 
formula has a more appropriate pH than a ready-made formula with something 
acidic added.  The other problem is that the source and type of ascorbate 
will affect your results.  Adding ascorbate salt and ascorbic acid are not 
the same thing and you may not always know what you are adding.

Adding ascorbic acid to Rodinal does help with grain size, but again, I am 
not sure this has anything to do with the ascorbate as much as it has to do 
with the pH change and that you need to buffer this pH change with borax to 
prevent infectious development.

I would encourage everyone who likes to experiment with developers to do 
three things: experiment wildly, record carefully and report cautiously from 
their own work.  

Marty


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Most people can only judge of things by the experiences of ordinary life, 
but phenomena outside the scope of this are really quite numerous.
        Shen Kuo - 'Dream Pool Essays'


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