[pure-silver] Re: fixer composition

From: David Foy <dfoy@xxxxxxxx>
Subject: [pure-silver] Re: fixer composition (was Re: Re: PMK)
Date: Fri, 28 Apr 2006 09:51:56 -0600

> Typical C-41 and b/w minilabs are designed to move the film straight 
> from the developer into the fixer (or bleach-fix). There is no 
> intermediate rinse and no stop bath (I believe E-6 minilabs have a water 
> rinse after first development). Clearly for C-41 and b/w the folks at 
> Kodak, Noritsu, and Fuji see problem from a chemical point of view, or 
> for any reason having to do with processing consistency.

Minilab machines use mechanical squeegee to remove developer from the
film surface, and this is not the same as transferring film and paper
in manual processing from dev to fix.

C-41 is also a different story. In color process (and b&w reversal
process) silver image first formed is unnecessary and will be
removed by bleach. At this point, any silver staining (such as
dichroic fog) will be removed altogether. Therefore they need not
worry about this sort of issues. In b&w negative processing, the image
formed in the first developer is what you keep, and you'll want to
minimize the risk of silver stain occuring in the fix bath.

Again, a brief water rinse is sufficient to prevent this problem,
although longer (1 min) wash may be needed to stop development.

Despite the name "stop" the most important role of stop stage is to
remove developer, rather than completely arresting development
reaction.
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