A private conversation about sulfite and bisulfite for clearing gum
prints made me think of a post that's been stuck in my outbox for a
couple of weeks, which I will send on in a minute. It was written in
reference to a different discussion that's gone on past, but I think it
relates to this discussion as well.
The question is, what does "dichromate stain" consist of? I'm sure I
don't know exactly, but I'm not sure anyone else does either. My
correspondent seems to believe that it consists mostly if not entirely
of dichromate, which I rather doubt since most if not all of the
unreacted dichromate escapes easily out of the crosslinked gum into the
wash water.
A different clue is in the observation, reported in the following post
with the heading "Color of 'tanned' gum'" that if brown-stained
crosslinked gum (not treated with a clearing agent) is scraped off a
support while still wet, the resulting sludge is a deep green, which
would suggest that it consists mostly of CrIII.
Katharine Thayer
Received on Thu Oct 14 10:19:04 2004
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