From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 03/29/01-05:31:13 AM Z
Dave Rose wrote:
> I suppose it is possible to mix combinations of ammonium dichromate and
> potassium dichromate to fine-tune speed and contrast with gum, ...
With the Pt/Pd process, there is a difference, and not just speed and
contrast. The sharpness, clarity, and look of the print can be
effected. I have used ammonium dichromate, potassium dichromate, and
potassium chlorate alone and in combination as contrast agents in the
coating mixture. I have used potassium dichromate as a contrast agent
in the developer. I have noted differences in the look of the print
(beyond just contrast) from each of the agents or combinations.
Sometimes I have intentionally given the negative less contrast so I
could get the effects of the contrast agent(s) without the gain in
overall contrast. (Understanding that contrast from negative
development also differs from contrast from coating agents.)
> The manipulation and control possible with gum is a fascinating topic. I
> could go on and on, but I'll stop here.
The manipulation and control possible with the Pt/Pd process is a
fascinating topic. At times a nuance is what really makes a print
great. I too could go on and on, but I'll stop here.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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