[pure-silver] Re: D-Max with pyro

Pyrogallol was a popular developing agent in the 19th and early 20th
centuries.  I believe one of the reasons why it fell out of favor is
when films could no longer be developed by inspection.  There was a
problem of inconsistent staining.

-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Jeffrey Thorns
Sent: Tuesday, December 13, 2005 9:36 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: D-Max with pyro


I, too, would like a better understanding.

I will be the first to admit that I am not the most exacting darkroom 
worker, but I use the same thermometer, tanks, reels, water, 
developer (distilled for developers!) and fixer all the time. I vary 
the time very little (5-10%) and am careful to clean all equipment 
immediately after use.

And yet I have seen some rolls with very pronounced stain, and others 
with just an overall, slight warm color. If I can't count on a 
significant stain, I might as well go back to a 'normal' developer.

Signed,

Perplexed in Portland


>
>
>>I have found that a wash
>>with Sodium Metaborate makes a big difference
>
>Others claim that an alkaline rinse like metaborate does nothing more 
>than increase the overall stain and contributes nothing to the image. 
>Since this stain is not formed during image formation I would tend to 
>agree with this comment.
>
>   I have begun to question my understanding of the nature of the
>pigment produced by Pyro stain developers. I know it is a pigment 
>and not a dye and that the pigment is very permenant, but I am not 
>at all certain of its reaction to pH. Dyes are well known to react 
>to changes in pH, which can decolorize some of them but I thought 
>that the Pyro stain was immune to this. My undertanding is also that 
>it can't _wash_ out. The stain image _can_ be removed by a Peroxide 
>bleach but this is pretty far from anything which happens in normal 
>processing.
>   The use of after treatment using deveveloper, claimed to intensify 
>the stain, evidently only adds overall stain, the equivalent of fog, 
>which is undesirable.
>   The stain is a result of the reaction products of the developer. 
>It is certainly variable with the formulation of the developer, for 
>instance, large amounts of sulfite can eliminate it and there are 
>formulas in the literature for non-staining Pyro developers. 
>However, once formed the pigment seems to be quite permanent.   I 
>wonder if Ryuji has any thoughts on this.
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