Formalin

On Fri, 18 Aug 2006 01:29:59 GMT, "Alan Smithee"
wrote:

I think you're thinking formic acid. I think they're close but not quite the
same. CH2O (formalin) and CH2O2 (methanoic acid). I think the latter I've
used in bee keeping.

Formaldehyde degrades into formic acid via oxidation reaction, I
believe.
--
Central Maryland Photographer's Guild - http://www.cmpg.org
Strange, Geometrical Hinges - http://sgh.rnovak.net

"Richard Knoppow" wrote in message
ink.net...

"Rob Novak" wrote in message
...
On Thu, 17 Aug 2006 05:37:03 GMT, "Alan Smithee"
wrote:

What is formalin used for in a darkroom. Found a bottle of
it. Does it have
any use in black and white photography?

Used to preserve and stabilize dyes in color negative and
slide films.
Not useful in B&W processing, AFAIK.
--
Central Maryland Photographer's Guild -
http://www.cmpg.org
Strange, Geometrical Hinges - http://sgh.rnovak.net

Formalin is an aqueous solution of Formaldehyde, 40% by
volume or 37% by weight. Formalin was formerly used as a
hardener preceding some treatments that significantly
softened emulsions. An example is Kodak Special Hardener
SH-1
Kodak SH-1
Water 500.0 ml
Formalin 10.0 ml
Sodium Carbonate, dessicated 5.0 grams
Water to make 1.0 liter

The crystalized form of Formalin, called Paraformaldehyde,
is used in some lithographic developers but Formalin can
also be used in them. In these developers the Formaldehyde
acts as a source of Hydroxide rather than as a hardener. It
encourages what is called infectious development, which is
desirabel in a lithographic developer but not in standard
developers.
Formaldehyde, in various forms, was and is used as a part
of a final rinse for color films as a dye stabilizer. More
modern formulas have substituted other substances because
Formaldehyde is quite toxic and has an unpleasant odor. It
is still supposed to be a superior stabilizer.

Would this be applicable to any films still used today? Sheet films. Alt
photography? I'm thinking as a hardener for gum.

"Alan Smithee" wrote in message
news:67kFg.420307$iF6.352119@pd7tw2no...

"Richard Knoppow" wrote in
message
ink.net...

"Rob Novak" wrote in message
...
On Thu, 17 Aug 2006 05:37:03 GMT, "Alan Smithee"
wrote:

What is formalin used for in a darkroom. Found a bottle
of
it. Does it have
any use in black and white photography?

Used to preserve and stabilize dyes in color negative
and
slide films.
Not useful in B&W processing, AFAIK.
--
Central Maryland Photographer's Guild -
http://www.cmpg.org
Strange, Geometrical Hinges - http://sgh.rnovak.net

Formalin is an aqueous solution of Formaldehyde, 40%
by
volume or 37% by weight. Formalin was formerly used as a
hardener preceding some treatments that significantly
softened emulsions. An example is Kodak Special Hardener
SH-1
Kodak SH-1
Water 500.0 ml
Formalin 10.0 ml
Sodium Carbonate, dessicated 5.0 grams
Water to make 1.0 liter

The crystalized form of Formalin, called
Paraformaldehyde,
is used in some lithographic developers but Formalin can
also be used in them. In these developers the
Formaldehyde
acts as a source of Hydroxide rather than as a hardener.
It
encourages what is called infectious development, which
is
desirabel in a lithographic developer but not in standard
developers.
Formaldehyde, in various forms, was and is used as a
part
of a final rinse for color films as a dye stabilizer.
More
modern formulas have substituted other substances because
Formaldehyde is quite toxic and has an unpleasant odor.
It
is still supposed to be a superior stabilizer.

Would this be applicable to any films still used today?
Sheet films. Alt
photography? I'm thinking as a hardener for gum.

I can't answer specifically except that those making gum
or oil prints seem to be using other hardeners. I suggest
looking up the archives of the Alternative Processes mailing
list for more. A Google search for _alternative processes_
should find it. The formula above is one Kodak used to
recommend for use before certain reducers or intensifiers
that had considerable softening action. Most modern films
are hardened differently in manufacture than those of the
1930's to the 1950's and many have additives to the gelatin
again making them more resistant to swelling and softening
by both temperature and chemicals.


--
---
Richard Knoppow
Los Angeles, CA, USA