Re: Color of Vandyke Browns, was First Kallitype

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From: Joe Portale (jportale@gci-net.com)
Date: 01/02/01-09:11:49 AM Z

For what it is worth, heat is the first recorded method of toning all of the
earlier processes. Herschel reported that a salt print when a hot iron was
passed over the image showed a definite color shift. I do not know the
chemical changes that occur during this process. But it would be safe to
assume that heat drives out any humidity contained in the image, rearranging
the image crystal molecules. The effective color of an image is directly
related to the crystalline structure that forms the image. Bigger crystals
reflect a different wavelength than small ones. Different metals have
different sized crystals. The application of heat changes that surface
structure forming the color changes. Color shifts due to chemical toners
operate on a different level, but the underlying principle is the same. The
crystals of silver are plated with another metal changing the size of the
image forming crystals. This plating alters the way light is reflected or
refracted off the image forming crystals.

I am not a chemist/physicist, nor do I play on television.

Joe

----- Original Message -----
From: Sarah Van Keuren <svk@steuber.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, January 01, 2001 7:00 PM
Subject: Re: Color of Vandyke Browns, was First Kallitype

> Sandy, yes, I have found that if a vandyke print is flattened in a
drymount
> press with the image in direct contact with the hot metal, or if it is
> ironed directly (without steam), the color change that you noted occurs. I
> thought that it had to do with contact with metal but maybe humidity
within
> the paper is brought to the surface of the image and causes the image
shift.
>
> Sarah Van Keuren
>
> > Just curious, though, in addition to the gray/black colors you sometimes
> > have seen are, there other colors that one can get from Vandyke? I am
> > curious because a while back I used the dry mount press to flatten a
> > Vandyke print out and it changed the color from a light chocolate black
to
> > a very deep dark/black much more neutral in tone. When I put the print
in
> > the dry mount press it still had some humidity in it, though it was dry.
> >
> >
> > Sandy King
> >
> >
> >
> >
> >
> >
>

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