Re: Dry Plate Speed & Shelflife

From: MARTINM <martinm@SoftHome.net>
Subject: Re: Dry Plate Speed & Shelflife
Date: Wed, 02 Mar 2005 11:32:36 +0100

> Incidentally, as early as 1850 Poitevin modified this process for
> the making of gelatin coated silver halide emulsions on glass
> plates...

Now I'm back in office and have refs. According to Eder, Poitevin
coated plain gelatin, immersed in AgNO3 solution, dried and exposed it
to iodine vapor to sensitize. The speed was much slower than
Daguerreotype plates, and this process never became popular.

Incidentally, Ostroff and James (1972) reported that the earliest
attempt of silver gelatin process was 1850 by Bingham, describing his
process in his book Photogenic Manipulation. Research at Smithonian
Institution verified that Bingham invented this process. Joel Snyder
of Chicago followed Bingham's direction and verified it worked as
described. His method was to coat glass with gelatin (isinglass) mixed
with iodide, and immerse this plate in AgNO3 solution.

Ostroff, E. and James, T. H. 1972. Gelatin silver halide emulsion: a
history, J. Photogr. Sci., 20, 146-8.

People at Kodak Labs in Rochester as well as Harrow did chemical
assays on some of Talbot's material and found that gelatin was present
in their sample materials. Paper stocks were already a serious issue
in Talbot's process, and so he later prepared papers with albumen,
starch and gelatin to reduce the roughness and porosity of the paper
surface. Besides, according to Fritz Wentzel (an all around geneus in
photographic engineering) citing Davanne and Girard's research on
difference in quality of papers manufactured in France, England and
Germany, English paper manufacturers generally sized their paper with
gelatin while continental manufacturers used starch and resin. So I
have little doubt that gelatin was a part of photographic process from
fairly early point in the history of photography.

--
Ryuji Suzuki
"Well, believing is all right, just don't let the wrong people know
what it's all about." (Bob Dylan, Need a Woman, 1982)