From: Katharine Thayer (kthayer@pacifier.com)
Date: 09/22/02-02:18:08 AM Z
FDanB@aol.com wrote:
>
> Judy said in her message...
>
> >But Dan --
> >where was the "gum curve"? I opened every one that looked possible, but
> >the only one that seemed at all possible was the cyanotype curve, which I
> >loaded & will try.
>
> There ain't one. I solicited gum curves from this very list among other
> places and was told that there were too many variables to make one
> person's curve useful to anyone else. So yes, you must do your own
> homework on designing/modifying such a curve.
>
Yes, Dan wrote me when he was working on the second edition of his book
and asked if I would share my gum curve, and I answered that I didn't
think it would be generalizable to anyone else. Not only will the curve
differ depending on the substrate used for the negative, the printer
used for the negative, the ink used for the negative, the exposure light
used in the gum printing, as well as the paper and gum and gosh knows
what all else, but my own curve changes over time depending on the
series I'm printing and how I intend to print it, for example if I
intend to print it especially light or especially dark.
I want to underscore what someone already said; it's how the negative
prints on gum that matters, not how the negative itself reads on a
densitomer. The negative is a means to an end, not an end in itself. And
while it's a good thing to start with a negative that will yield the
desired result, the controls available to the gum printer in the
printing process itself can compensate to some extent for shortcomings
in the negative, and of course we all know, I assume, that gum prints a
fairly short scale and that to get all the tones in a negative with a
longer scale, you have to do multiple printings.
Last year when I was both changing the paper I was printing gum on and
also changing from paper inkjet negatives to transparency material, I
noticed that the test prints I was generating would provide a great
demonstration of how much control the gum printer has either by changing
printing variables or by changing the curve on the negative. I intended
to select 10 or 12 of those test prints and post them on Bostick &
Sullivan with annotations, and even got permission from Dick to do so,
but was too busy for several months to even think about it then, and now
the test prints are no longer available since I've used some for
subsequent tests of protective coatings and so forth and the rest have
got buried and scattered. My point in all this is simply that with gum,
one can control the tonal scale in the final print to a great extent by
controlling the printing variables, as well as the negative, so while I
try to start with the best negative possible, it's the skill of the gum
printer, as Dave said in another context, that really makes or breaks
the final print, in my opinion.
Katharine Thayer
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