Re: oil-print-glyoxal??

From: Katharine Thayer <kthayer@pacifier.com>
Subject: Re: oil-print-glyoxal??
Date: Mon, 27 Dec 2004 15:32:10 +0000

> I agree with you that very little of this discussion provides a useful
> answer to Henk's question, which was: what about oil printing, where the
> point in dichromating and irradiating the gelatin is to create a matrix
> which functions in such a way that the swollen gelatin repels the oil
> and the hardened gelatin accepts it. What about the unhardened gelatin
> that remains in the highlight areas after the print is inked, was his
> question.

I didn't quite get his question clearly. Based on what you said above,
practically the only difference is amount of swelling. That is, amount
of water absorbed in gelatin matrix is the only difference unless
unhardened gelatin is purposely washed away.

But I thought he was more worried about mold/bacteria. Gelatin is
susceptible to proteolytic enzymes used by many
microorganisms. Biocides commonly used are washable during processing,
so if you want biocide to remain in your material, they should be
treated with biocide after processing. There is (was?) a wetting agent
similar to PhotoFlo but containing a biocide, sold by Tetenal. I never
used it though.

> Since people have been making oil prints for a hundred years or so,
> there should be data available from photography curators about whether
> the unhardened gelatin in highlight areas poses a problem for longevity
> of these prints; I guess I'd leave it to them to have the last word on
> Henk's question. The rest of us, as helpful as we're trying to be, are
> just guessing.

By the way, if what he is doing is same as colotype (not calotype of
Talbot), quite detailed instruction is found here:

http://web.kyoto-inet.or.jp/people/artbooks/colloP.htm

(It's in Japanese - sorry!)

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)