From: Katharine Thayer (kthayer@pacifier.com)
Date: 12/17/01-09:40:03 AM Z
When I wrote my "reality check" yesterday I debated whether to bring up
my own experience and data relating to the pigment test and decided
against it, because (1) my point was that even if that test had been
utterly and devastatingly disproved, that would not undermine or
challenge in any meaningful way the basic usefulness of the texts that
include it, and (2) I was willing to introduce some perspective on
someone else's behalf, but I didn't think that test mattered enough to
me to make an issue of the test itself.
But as I've thought about it, I've come to believe that we can't really
have a meaningful discussion about this without having the complete
picture, which includes the fact that my experience and data actually
support the test rather than the challenge to it.
Until I discovered Crawford, I was having some trouble with pigment
staining, but one evening with Crawford and that pigment test (or a
quick-and-dirty approximation to it) banished pigment staining from my
prints forever. I didn't follow the test exactly as written; I've never
owned a pipette or a gram scale and wasn't interested in that kind of
specificity anyway; I just wanted a ballpark place to start. (I rather
think that anyone who would actually do that test as written is probably
too left-brained to succeed in gum printing, but that's neither here nor
there.) I used the basic principles of the test rather than the exact
instructions, but it's my understanding that it's the basic principles
of the test that are under attack. Comparing the stain test to printing
tests, I found, just as Crawford said, that if the pigment stained in
the float test, it would also stain in printing, and that there was a
direct correlation between pigment concentration and staining. It only
took a few tries to develop an intuitive understanding of the range of
pigment concentration that would print well (with good maximum density,
by the way) with clear highlights, and to understand that in general I
had been using too much pigment, and I've never had a staining problem
since.
The argument that pigment and gum alone will have different staining
properties than pigment and gum and sensitizer is a persuasive argument
theoretically; however I haven't found it to be true empirically. I
recently read the unpublished gum manual of a person I know to be a
careful tester; he agrees in principle that the test is bogus and that
adding the sensitizer changes the equation, but his data show that with
the sensitizer added the pigment stains MORE than without it. I
understand Judy's conclusion was that with the sensitizer added the
pigment stains less, in fact it doesn't stain at all; it flakes before
it stains. With Judy saying sensitizer makes the pigment and gum stain
less, my friend saying sensitizer makes the pigment and gum stain more,
and me saying that I don't think it makes a heck of a lot of difference,
there's obviously not consensus on this issue.
When I came on the list one of the things I said was that I'd found the
pigment test in Crawford very helpful in learning to control pigment
stain. Some kind soul told me that I shouldn't say that here, so I
didn't say any more about it, but it's still true.
Today I have run a replication of my early approximations of the test
and the results come out the same as they did before: (1) stain
increases directly with pigment concentration, and (2) staining shows up
in the float test at about the same concentration as staining in
printing.
After these tests have dried, I will upload them to the Bostick &
Sullivan site so that people can see them for themselves. I'll make an
announcement here so you'll know when they are there. It may be a day or
two.
Just to underscore the point I was making yesterday about David Scopick,
the fact that my findings differ from Judy's does not mean that I think
she is a liar, or an incompetent tester, or that she should be
discredited forever as an authority, or even that she is WRONG. It just
means our data differ, that's all.
Katharine Thayer
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