From: Judy Seigel <jseigel@panix.com>
Subject: Calling LIAM RE: update on lumen prints
Date: Thu, 15 Sep 2005 22:19:07 -0400 (EDT)
> There's a bleach that removes ONLY the silver halide -- that is, the part
> that's not yet developed to metallic silver, which is why you have to fix
> in the 1st place.
Bleach is usually a solution that removes metallic silver, not silver
halide. Some bleach dissolves metallic silver into the solution, while
others oxidize metallic silver to silver halide. Fix is the solution
that removes silver halide.
To go back to the original question, fix is necessary for long term
stability. This is regardless of whether the image part is toned with
noble metal or not. If silver halide is not removed, they can easily
get converted to silver sulfide by environmental pollutants, or even
reduced to metallic silver over time. Both cases the result will
appear as severe image stain.
> If memory serves (which it may not) that's a potassium
> ferricyanide with potassium bromide and --- hydrochloric acid? I have it
> somewhere, but LIAM will know... LIAM! Calling LIAM !
It is very dangeours to mix ferricyanide with mineral acids. This is
a known way to liberate cyanide gas by decomposing ferricyanide.
Either way, using ferricyanide bleach in the original context would
remove image but not the unexposed silver halide.
Received on Fri Sep 16 10:16:36 2005
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