From: Etienne Garbaux (photographeur@softhome.net)
Date: 09/07/03-10:22:03 AM Z
David and Ryuji wrote:
>> I am aware that gelatin is only one of several effective subs [...]
>
> But I don't know what else would work well on glass.
Sodium silicate, isinglass, and albumen are all successful subs for gelatin
on glass. A number of modern synthetics are probably "better," but all
three of these will bond gelatin to glass strongly enough that if you tear
the gelatin off it pits the glass.
Some people put the emulsion down directly on the sub, others use a layer
of chrome-hardened gelatin in between. I only do that when I'm dyeing the
hardened layer to act as an anti-halation layer.
If you get the glass properly clean (see below), chrome-hardened gelatin is
an acceptable sub, or you can even get by without a sub if you keep
processing temperatures and developer alkalinity moderate.
The hardest part is getting the glass CLEAN. You need to SCRUB the plates
in a strong, HOT soap solution followed by a strong, HOT acid bath followed
by a strong, HOT alkali bath followed by a strong solvent bath (nitric
diluted 1:1, concentrated sodium hydroxide, and acetone, in my case) with
distilled water washes in between and after, then a final dip in acetone to
make them dry quickly. The acetone must be reagent grade, not hardware
store, which contains traces of oil and other junk and will undo all of
your hard work. If you have benzene [note to our Brit colleagues: NOT
benzine], and are willing to work with it, that's even better. Yes, the
in-between washes need to be distilled water, not tap water. Once you've
gotten the glass clean, you'd be surprised how well gelatin adheres with no
sub.
Best regards,
etienne
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