rurmonas@senet.com.au
Date: 12/09/02-05:19:25 AM Z
Quoting Sandy King <sanking@clemson.edu>:
> I was thinking on the assumption that a 3% citric acid clearing bath
> could remove the soluble iron compounds at any point in the wet
> processing procedure. What you are saying is that the soluble iron
> compounds are actually changed in some way with any alkaline wet
> processing that takes place before the compounds are removed, right?
What I have noticed is that washing FAC in an alkaline wash
does form some low solubility iron compunds. I cannot say
if these are "bad" iron compounds or not. I suspect that
a VDB print does contain an amount of iron salts, but I have
not been able to test this (it is beyond my simple methods).
There could also be iron salts which have poor solubility in alkaline
conditions, these however, would be removed by a later acidified wash.
> If so, this would also have implications for regular kallitype
> processing as well as VDB and n theory I should eliminate the water
> rinse that I have been using between development and the citric acid
> clearing bath. This assumes of course that ferric oxalate and ferric
> ammonium citrate compounds function alike at this particular stage.
I have not tried any oxalate based processes so cannot comment if similar
effects occur.
Note that VBD solution has tartaric acid and so I would expect some
Ferric Tartarate to be in the solution. What percentage, and how
much of an effect this has, I do not know.
> In any event your processing proposal makes sense. However, what
> percent solution of citric acid do you propose in step #2?
Sorry I have not investigated this. If I get some time,
I shall try some experiments.
Richard
--- Richard Urmonas rurmonas@senet.com.au ------------------------------------------------- This mail sent through SE Net Webmail http://webmail.senet.com.au
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