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Re: Gum vs. Kallitype
On Thu, 23 Mar 2000, Andre Fuhrmann wrote:
> Permawash, I take it, is a washaid. Washaids usually contain soda. Soda
> attacks gelatine. With standard silver prints this is not much of a
> problem as the gelatine is fairly tough and will survive a minute or two
> (but try 5 or even 10 minutes!). Glyoxal, however is not a very effective
> hardener. My advice: Clear the gum print in alun (may take 30 minutes or
> more) -- this will further harden the gelatine. Then let it rest for a
> couple of days. Omit step 5 and extend step 6.
Now just a darn minute, Andre -- you can't drop a line like that into our
tea party & then take off. What's this about "glyoxal is not a very
effective hardener"? You force me to take a leaf from Jeffery's book and
demand reference & source -- or at least a few particulars. I've been
doing some more tests on glyoxal, finding that length of hardening is a
factor. For instance, 5 minutes in glyoxal much better than 1 minute....
perhaps more is even better... Still, you probably mean less effective
than formaldehyde ... Can you add any ("evidentiary") details?
As for "clearing gum" in alum. Consensus of conservators seems to be that
alum bath degrades the color -- especially ye gods 30 minutes. (No I can't
document, but have read 5,627 times.)
HOWEVER, why clearing bath for gum anyway? Except in the RARE case when I
have done something really dumb, like leaving emulsion on paper overnight
in unairconditioned August, simple water soak (up to 2 hours) clears any
residual dichromate stain...
AND, isn't anybody going to ask Keith why he's putting VDB over gum? It's
a dark & lonely job, but someone has to do it, so here goes: Keith, tell
us why you're putting VDB over gum. I admit I tried it myself a couple of
times but got only a kind of murky brown. What did I miss? Maybe you're
putting only in areas? Or?
Judy
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| Judy Seigel, Editor >
| World Journal of Post-Factory Photography > "HOW-TO and WHY"
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