From: Phillip Murphy (pmurf@bellsouth.net)
Date: 03/31/03-04:46:51 AM Z
Hello Agustin,
When developing a Daguerreotype using cold mercury, the image tends to be blue
because of the small particle size.
To increase the particle size and cause the image to refract light of the longer
wavelengths, one needs more concentration
of mercury vapor. Using heat is the obvious way of increasing the concentration
and that is how the traditional Daguerreotype
process functions. A few years ago, a guy named John Hurlock invented a method
of increasing the concentration of
mercury vapor using a vacuum desiccator, this increases the size of the
silver-mercury particles in the image which makes
for some very interesting Daguerreotypes. (or are these Hurlocktypes?)
The method is simple. In order to increase the partial pressure of the mercury
vapor, you decrease the pressure of the atmosphere
surrounding the Daguerreotype plate.
First, obtain a vacuum desiccator. These can be found through most any
scientific supply house. A glass
desiccator isnt' necessary ; Bel-Art makes one that is plastic and affordable.
You'll need a light tight cardboard box or two to keep
the desiccator in while development takes place. (unless you use a darkroom)
Also, you'll need a way of creating the vacuum. Plastic water aspirators are
cheap
or you can find a hand pump at any local auto supply. (they're used for bleeding
brake lines).You'll want one with a gauge. If you
can afford the luxury, a vacuum pump is best because you can achieve a greater
vacuum in the desiccator.
Make a little rack to hold your plates in the desiccator. You can develop as
many plates at once as you can fit inside.
After exposure in the camera (or contact printed), place your plates into the
desiccator with a small pool of mercury held in
a glass petri dish. Evacuate the sealed desiccator to a 23 to 27 inch vacuum.
By the way, plates need not be developed
right away. You can delay development of your plates for several hours, thereby
developing them all at once if you have a long
session of image making. You'll want your desiccator to be in a dark warm place
during development. You can safely observe
the development in your darkroom using a yellow or red safelight since the
mercury cannot escape the desiccator if it is properly
sealed (use vacuum grease on your desiccator if necessary). Images developed
around four hours will be "blue front" and those
developed from 12 to 24 hours will have more neutral values in the image.
When development is finished, be sure to release the pressure valve of the
desiccator very slowly, otherwise you can cause a rush
of air into the desiccator creating tiny spots on the plates. Clear and gild
the images as you normally would.
hope this helps,
Phillip
PS: Anyone who attempts this method should read the MSDS regarding Mercury.
Just Google for the information.
If Mercury is not handled properly, it can cause chronic health problems.
Agustin wrote:
> Now that you mention it Philip, is there a reasonable way to develop
> Daguerreotypes with cold (room temperature) mercury?. I´ve tried it with the
> normal process (Iodide and mercury at 60 Cº) and the developing times are
> arround 1-5 minutes. What are the drawbacks when developing with room temp
> mercury?. That might save me some health problems in the future!
> Thanks in advance.
>
> Agustin Barrrutia
>
> ----- Original Message -----
> From: "Phillip Murphy" <pmurf@bellsouth.net>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Sunday, March 30, 2003 7:52 PM
> Subject: Slowest development / was Re: emergency question regarding
> cyanotype
>
> > It would be curious to see a list of slowest alt-photo processes. Not
> that one
> > can not drag these
> > processes out ( example would be many many layers in building an image).
> But a
> > list of process insensitivity to
> > actinic light would interesting.
> >
> > The longest times that come to mind for myself is working the
> Physautotype, the
> > Becquerel developed
> > Daguerreotype, and the cold-mercury developed Daguerreotype. The range is
> from
> > four to thirty-six hours.
> >
> > Anyone else practicing patience out there? Perhaps the pinhole
> practitioners
> > have some remarkable times.
> > Didn't someone make an image that lasted months to create with a pinhole
> camera?
> >
> > -Phillip
> >
> >
> >
> > "Christina Z. Anderson" wrote:
> >
> > The second part of your question: timewise, if it is gray and rainy
> > outside, expect a very long exposure with traditional cyano. Someone will
> > correct me if I am wrong, but if I remember, it is the longest time of the
> > alt processes, and even moreso if you are using traditional cyano mixed
> 1:1
> >
> > >
> >
>
> ---
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