Re: Measuring Pt/Pd Negative Density Ranges

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From: Judy Seigel (jseigel@panix.com)
Date: 06/25/00-08:54:50 AM Z


On Sun, 25 Jun 2000, Eric Neilsen wrote:
> ... The combinations of chemicals sources,
> concentrations,
> light sources, humidity ranges and paper give a big change in speed and
> contrast. It could be done for a specific user and/or set of variables
> but not
> all pt/pd printers work the same. DOP, POP, DOP/POP. Jeffrey had it
> right.
> Learn by seeing and adjusting your eyes to your process. Absolutes work
> in a
> closed environment but not so well in pt/pd printing.
>
> "i.e.drops [recommended] " of what? contrast agent(s)? Pt vs. Pd ? FO
> to Pt/Pd?
> ?????

Extrapolating from cyanotype, which I suspect is more similar to pt/pd
than is generally credited (except of course for aura and $$$$), there are
even more variables, such as double coating, which makes an enormous
difference under SOME conditions, the *particular* lot of a given paper,
whether the mfr sized it summer or winter, and did you say light source?
I've found denser blue with bulbs X than Y. Etc.

But anyway Eric, if you get "absolutes" to work in YOUR environment you're
a better man than I am... they hardly don't ever around here. But puts me
in mind of the gentleman in a workshop who was mightily, um, peeved, and
obviously skeptical of my expertise, when I couldn't give him a "curve"
for gum of precise relationship between exposure and density. (Turned out
he was an actuary.)

Judy

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