[alt-photo] Re: Daguerrotypes and Herschel - response from Ken Nelson, master daguerreotypist

[gumprint at gmail.com]

Malin,

I forwarded your question to a long-time colleague, Ken Nelson, master
daguerreotypist (ASU, Eastman House, Kodak), currently in Washington state.


>>

From: *Kenneth Nelson* <dagman_kn at hotmail.com>
Date: Wed, Aug 31, 2011 at 4:04 PM
Subject: RE: [alt-photo] Re: Daguerrotypes and Herschel
To: *gumprint at gmail.com*

 Hi Carole, good to hear from you.


Sir Humphrey Davy, no stranger to very early experiments toward the
invention of photography, was the first to identify Sodium as an element in
1806. Sir John Herschel identified Sodium Thiosulfate (then called
'Hyposulfite of Soda') as a solvent for silver salts in 1819. Daguerre and
Fox-Talbot both used concentrated solutions of Sodium Chloride to 'fix'
their early efforts. James Rielly, author of *The Albumen and Salted Paper
Book*, suggests that this technique was more of a 'stabilization' than
'fixation' and that while the stabilized silver salts didn't react to light
nearly as much as before, the salts were left in place in the paper or on
the daguerreotype plate. That was more of a problem for paper prints, since
a huge amount of silver salt would be left in place, compared to the tiny
amount on the surface of a silver plate. And, given that at several of
Daguerre's very early examples have made it through history to the present
time,  the concentrated table salt stabilization was pretty effective for
daguerreotypes.

Reilly writes "The discovery of the fixative properties of sodium
thiosulfate (or "hyposulfite of soda" as it was known then) was made in 1839
by Sir John F. W. Herschel. He had heard that both Talbot and Daguerre had
evolved photographic processes, and decided to make some investigations
himself. He first applied sodium thiosulfate for the purpose of fixing
silver chloride papers on January 29, 1839. The idea came to him because of
some observations he had made in the years 1819 and 1820, when he discovered
the substance sodium thiosulfate and noticed that it was a solvent for
silver chloride.2 A short while later he communicated his epochal discovery
to Talbot, who up to this point had not been truly fixing but merely
"stabilizing" with a strong solution of sodium chloride. Talbot at first
disdained "hypo," but later incorporated it into his own process, as did
Daguerre, who had also been "stabilizing" with a strong sodium chloride
solution (in a stabilizing treatment the silver chloride is not removed, it
is merely changed into a less sensitive form)."

(Personally, I think that the concentrated table salt solution did in fact
remove the unused silver salts from the surface of the daguerreotype plate,
since there was so much solution and so little silver salt to be removed.
One possible mechanism might be that the table salt solution, being made of
Na+ and Cl- ions, was strong enough to crack the solid silver iodide
crystals on the plate and carry off the I- ions, leaving the silver in
place. But I'm not enough of a chemist to assert this with any authority.)

Carole, please pass this on to the alt-photo folks, and don't be shy about
including my email address.

Best regards, and glad to hear you're enjoying the rejuvenated dag!
Ken <<


Hope this is of help to you.


Best,

Carole



On Tue, Aug 30, 2011 at 4:22 PM, Alternative Photography <
alternativephotography at gmail.com> wrote:

> I have a question...
> Any photohistorians out there? Would you happen to know if daguerrotypes
> were permanent before Herschel got involved? Or where they only able to fix
> it after Herschel invented hypo?
> All the best,
> Malin
>
> --
> *´¨)
> ¸.•´¸.•*´¨) ¸.•*¨)
> (¸.•´ (¸.•*Malin Fabbri
> Editor, AlternativePhotography.com
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