----- Original Message -----
From: "Anthony Farr"
Subject: Re: XTOL and bubbles--follow up
> Increases in total immersion time in ~any~ stage of the
process can
> contribute to an increase in apparent grain size due to a
phenomenon
> called "silver migration", where the softened gelatin allows
the
> developing silver grains to lose their even distribution and
draw
> together into larger clumps. This was my experience when I
tried
> Rodinal at 100:1 dilution, it produced larger fuzzier grains
than at
> lower dilutions, I much preferred the crisper graininess I got
at 50:1
> dilution.
Clumping is mostly a problem with long developing times. The
actual wet time is less significant. Also, developers with
silver sovents (Microdol X is a good example) will cause
clumping more than developers without (I think D-76 is an
example of this, but I don't have my formulary handy at the
moment to check)
>
> Silver migration can also arise from needlessly long washing
but that's
> usually not a worry if you use a hardening fixer. However the
presoak
> occurs before hardening so it is important not to over-extend
its time.
Actually, emulsions have come from the factory prehardened for
close to 20 years now. The problem with a hardening fixer is
that when the gelatin in chemically hardened, it no longer
reacts well to processing. It doesn't wash as well, it doesn't
tone as well, and it doesn't take spotting as well.
William Robb
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