From: Katharine Thayer (kthayer@pacifier.com)
Date: 11/16/02-03:46:32 PM Z
Clay Harmon wrote:
>
> On Saturday, November 16, 2002, at 09:14 PM, Temi wrote:
>
> > Gum Dichromate - Two Questions
> >
> > No. 1 - When making gum prints, what are the pros and cons of using
> > either Potassium dichromate or Ammonium dichromate.
Ammonium dichromate is faster than potassium dichromate. If you use an
intense light, for example a 3000 watt plateburner or the direct sun,
the light and the fast sensitizer may in combination cause overexposure
and result in heavy deposits of reduced dichromate. So if you use an
intense light source, you may prefer the slower potassium dichromate.
There are differences of opinion about the relative contrast of the two
dichromates. Some say that ammonium dichromate prints flat and low
contrast, but that hasn't been my experience. In my experience, a good
range of tones and good contrast can be achieved with ammonium
dichromate; in fact I get a better print with ammonium dichromate than
with potassium; others find the opposite. You may have to try both and
judge for yourself.
Katharine Thayer
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