Another thing to ponder: in my stack of oddball pieces of paper,
there was a quarter-sheet of Arches Aquarelle that had been sized
with acrylic medium. I had cut a piece off this paper the day before
and printed a small tricolor on it from a file an offlist
correspondent had sent me to try to figure out a problem he was
having with his color balance. The tricolor printed perfectly: no
stain whatever on any of the layers, including the middle layer which
was the same mix of PR209 I used for the test strips described
below. (The file as he created it had a border around the image
which printed paper white, so any stain would have been very easy to
detect, and this border was pure paper white after the three
layers). But when I cut another piece off the same sheet of paper
and coated it with the same PR209 mix for these test strips, I got
immediate and irrevocable stain; it was one of those where you know
on the first brush stroke that you've got stain; the paper speckles
immediately in a way that you can tell is going to be permanent.
Why it would stain in one case and not in the other, when everything
is the same: the exact same piece of paper, same pigment mix (well-
stirred) same amount of the same dichromate, coated area about the
same size in both cases, same amount of brushing-smoothing, same
light, same environmental conditions, and the exposures for the print
were within the range of exposures for the test strips. But if the
very same things can yield such different results for the same
person, it should hardly be surprising that different things yield
wildly different results, or that different people using the same
things often get different results. Just another reminder that one
test does not a finding make...
kt
On Aug 3, 2006, at 1:47 PM, Katharine Thayer wrote:
> Okay, here's something to wake y'all up, since people are getting
> restless about getting no mail from the list:
>
> I've been printing PR 209 (quinacridone red) at four exposures,
> from underexposed to overexposed, on samples of all different kinds
> of paper. (I've got a little stack of paper odds and ends that I'm
> trying to use up). My goal was to try to see if it's true, as is
> often alleged here, that stain is related inversely to exposure, in
> other words that underexposed gum is more likely to stain than gum
> that has received more exposure. I figured if it were true, this
> effect would have to show up if I did a bunch of test strips at
> different exposures. After a couple of days of this, I have about
> 20 sheets of paper with four test strips on each, exposed at 1, 2,
> 3 and 4 minutes. Some of the papers are stained, some aren't. But
> in every case where there is stain, the stain is even across all
> exposures; there isn't more stain where it's less exposed (nor is
> there more stain where it's more exposed). The stain is simply
> constant across the entire coated area on the paper, which tends
> to support what I've said before, that stain is independent of
> exposure. All of these papers were developed for 1.5- 2.5 hours,
> since they were developed for the most-exposed strip, which was
> well over-exposed. The variation in the time required to develop
> the 4-minute exposure reflects the difference in speed between the
> different papers. Mark, I think, was asking a while ago if there
> are processes other than platinum in which, everything else held
> constant, different papers print with different speeds. I answered
> "Yes, gum." This experiment shows the truth of that assertion. I
> wish I could scan these for you, but my scanner is still in the shop.
>
>
> A result worth noting: A piece of Lana that had been sized with
> glutaraldehyde stained an overall soft pink, while glyoxal-sized
> paper stained not a whit, nor have I ever had glyoxal give pigment
> stain. I'm not drawing any particular conclusion from this ; it's
> just more data for the collective database.
>
>
> Katharine
>
Received on 08/04/06-10:30:58 AM Z
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