From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 06/07/02-03:15:07 PM Z
There is a misunderstanding that the anti-halation coating of film is
removed during processing. With the exception of Remjet on Kodachrome and
motion picture films this is not the case. The anti-halation coloring is a
dye in the anti-curl gelatin coating on the back of the film. It is not
removed but decolorized, usually by the developer. Its also decolorized,
but more slowly, by the fixing bath. A soak in any slightly alkaline bath
will remove it, Kodak Hypo Clearing Agent, which is neutral, will remove it
without undoing the hardening of hardened emulsions. So will a soak in
working strength print developer, but that will cause some emulsion swelling.
Some films have an anti-halation layer under the emulsion. Most of these
are color films but a few black and white films also have such coatings.
These are decolorized by the developer in exactly the same way as the back
coatings.
KHCA is also effective in removing sensitizing dyes which are persistent
as in T-Max and some other films.
---- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com
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