Re: Dry Plate Speed & Shelflife

> 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.

Yes, that's valid more or less for Poitevin's 1850 publication (CR: XXX.
1850,
p.647 - 650). Actually, he then used silver acetate.

Not so for the method he advocated for in 1851. Poitevin applied a mixture
of gelatin (+ potassium iodide in some cases) to coat a glass plate. He
exposed it to iodine vapor and inserted the plate into a silver nitrate
solution.
Regarding the potassium iodide, he says:
"La gélatine étant coupée en petits morceaux, on en prend 1 gramme que l'on
met dans une petite capsule de porcelaine avec 30 grammes d'eau distillée;
après une imbibition de dix minutes au moins, on fond à une douce chaleur,
puis on écume la dissolution et l'on y ajoute 15 gouttes d'une dissolution
saturée d'iodure de potassium (...)."
That document can be found in the (CR: XXXII. 1851, p.927-929, available
online at: http://gallica.bnf.fr/).

Martin

----- Original Message -----
From: "Ryuji Suzuki" <rs@AgX.st>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, March 03, 2005 12:34 AM
Subject: 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)
Received on Thu Mar 3 02:08:15 2005