RE: Daguerreotype base-metals - More

I believe the spelling is "Brashear", and there's a formula at
http://www.ecu.edu/chem/glassblowing/Data.htm#silver. It's the use of a
caustic alkali - ammonium or sodium hydroxide - that makes it
potentially dangerous; if ammonia could be used instead the pH is very
unlikely to ever reach the critical point (pH 12.9) beyond which
fulminating silver can form. However, I've (inadvertently) silvered the
insides of glass vessels with a simple solution of silver nitrate and
Rochelle salt. Don't remember the exact strength, but probably would
have been around 10% silver nitrate and 5% Rochelle (i.e. 10 g silver
nitrate + 5 g Rochelle salt in 100 ml pure water). Leave to stand
overnight and you should get an excellent mirror if the glass is clean.

Liam

-Original Message-----
From: Robert W. Schramm [mailto:schrammrus@hotmail.com]
Sent: 09 April 2004 00:56
To: alt-photo-process-l@sask.usask.ca
Subject: RE: Daguerreotype base-metals - More

There is another, older way to deposit silver on glass. It was
originally
used to make mirrors.
I cannot give you the formula but it should not be to hard to find. I
believe it is called the Brasheer
(sp?) process. The only problem with it seems to be that if the
chemicals
are left standing around there is a tendency for fulminate of silver to
be
formed which is, of course, very explosive and very sensitive. Thus is
some
of the early mirror-making plants there were disasterous explosions. I
think
I have an old telescopoe making book that has a formula in it, but I'm
sure
a research librarian could find the formula. Vacuum depositin is now
used
to "silver" front surface mirrors but that requires a pretty good vacuum

system and , if you have every worked with a vacuum system you know
that,
according to one of my old physics professors, "A vacuum is a hole in
space
surrounded by profanity." By the way, silver has the highest albido of
any
known surface. That means it reflects
a greater percentage of the light falling on its surface than any known
surface. I guess thats why it makes such sparkley jewelery. Also many
modern
first surface mirror are coated with a beryllium-aluminium alloy instead
of
silver because silver tarnishes. However, silver is still used but
over-coated with quartz.

Bob Schramm
Check out my web page at:

  http://www.SchrammStudio.com

>From: Gregory Popovitch <greg@gpy.com>
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: alt-photo-process-l@sask.usask.ca
>Subject: RE: Daguerreotype base-metals
>Date: Wed, 07 Apr 2004 21:53:47 -0400
>
> > I'd imagine too that the gold chloride gilding would help in
the > > prevention of oxidation. > >Maybe it helps a little,
but sealing under glass is still >necessary. Even after gilding the
image is very fragile >and easily scratched (though I have an old dag
which is >very scratch resistant! I don't know how they did that).
> > > Silvered glass, eh? No polishing you say? Intriguing!
> >Irwing Pobboravsky wrote about his experiences with vacuum
>deposited glass plates in the "Daguerrean annual" from the
>Daguerrean Society. Some problems are: >
>- silver don't stick to glass very well, so he would first
> deposit chromium, then a mixture of chromium + silver, and
> finally pure silver. Even then the metal layer may come
> off when processing (gilding)
>
>- the silver layer is extremely thin, so plates can be used
> only once (no repolishing)
>
>gregory

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Received on Thu Apr 8 18:47:35 2004