scanning pigment stain

On Fri, 2 Apr 2004, Katharine Thayer wrote:

> Judy Seigel wrote: (March 24, 2004)
> >
> In fact, I've just done some tests which I am about
> > to scan proving that his Great Gum Pigment Ratio Test of universal acclaim
> > is as wrong as I said it was 298 times. .
>
> So did you scan these data and are they somewhere where we can see them?

I scanned 6 of about 50 tests and will show them in Post-Factory #9, to be
finished any second now. Actually I have trouble believing that I'm the
only one who has done this sort of test -- or maybe I'm the only one
rash/cruel enough to mention it. I don't think that the scans by
themselves are going to convince anyone who doesn't want to be
convinced... among other reasons being that scans are so easy to fake. I'd
suggest rather doing one or two of the tests for yourself.

I wrote an article of approximately 1,978 words on the topic, tracing the
discourse & practice through the canon from 1901 to 1939, and so forth,
mostly in their own words.

Here are the last 2 paragraphs (this being brought up to Pine on the
clipboard has lost all apostrophes & quote marks, also a few dashes, but I
think is clear enough....)

======================

...as my own mini-salute to science, I demonstrate that (1) pigment stain
in a gum print changes with the dichromate concentration, and (2) pigment
stain may be less with the dichromate than without it. In figures A & B
above, both pairs have the same ratio of liquid, pigment, and gum, but the
right-hand strip of each pair has a greater concentration of dichromate.

Figure C, which by itself disproves Anderson (and took less than 10
minutes, not counting the soak), shows that the way Anderson-style
pigment-in-gum-only clears (or doesnt clear) in water does not necessarily
parallel the way pigment exposed in sensitizer clears in water. Since the
tests are no more difficult to make with the dichromate and exposure than
without, I have no theory about why Anderson omitted it.

In other words, Anderson had it exactly backwards. The control is
dichromate, not pigment-to-gum. There are of course many other potential
variables, but these are constant. The moral of the story is that no
matter how logical a system seems to the engineering mind, nature has a
logic of its own. Which is probably why real scientists test their
theories. They make mistakes, but rarely such foolish ones.

=============

There follow 7 footnotes & a caption for the scans which details the
procedure. This cannot be done without a 21-step or comparable
sensitivity guide. Not that wonderful prints and a good understanding
can't be gained by using what I'd call "picture negatives," but however
lovely the image, the ordered and numbered density in a specific range is
needed to establish this kind of info...

Here are the details, again with italics, quotes, etc. missing, but
the idea should come through...

===================

Figure A: Rowney Jet Black gouache, a new tube which (unlike the old one)
tends to pigment stain; paper is back of a print on Uno. Each strip has 4
drops of paint (slightly diluted with water to measure), 10 drops
lithographers gum, 10 drops sensitizer (6% am di at left, exposed 5 min.,
13% at right; exposed 4 min.), still-developed one hour. Six steps are
visible in left strip, but right strip, with twice the dichromate, didnt
clear at all. The haze is from attempting to clear with water spray.
(Exposures were modified in an attempt to match prints with different
concentrations of dichromate.)

Figure B: DS Thalo Blue on sized BFK, same proportions and times as A,
again dichromate is 6% and 13%, again more pigment stain in the 13% strip
to the right. Note that in both the stain is lighter just above the
highlight, then darkens progressively on the way to step 21. This is
because the emulsion becomes somewhat more viscous with some exposure.
Even though its not enough to be a step, it sinks into the paper less,
while progressively less exposure sinks in more. (And I again credit Mike
Ware for the explanation.) For a more dramatic example, see P-F #2, p.
38).

Figure C: Strip at left, the same Jet Black gouache on sized Fabriano,
pigment, gum, and sensitizer, exposed 5 min., yields 5-1/2 visible steps
and *clear whites.* The tone at right is the same proportion of color and
gum (4 drops to 10 drops) on the same paper, but a la Anderson, no
dichromate, no exposure; soaked one hour. (Need I say more?)

========

PS: The "tone at right" I speak of is about a 20% gray. The strip with the
dichromate cleared perfectly.

And maybe I should emphasize that the total amount of liquid and gum and
pigment was always the same. Only the CONCENTRATION of the dichromate
changed. (Except for the one that had no dichromate at all... It had LESS
total liquid, meaning a higher percentage of gum !!!!!! while the
"thinner" emulsion, thinned by the dichromate & exposed, cleared, as I
say, perfectly.) Notice also that I aimed at a mix of "proper" well sized
paper and "bad" ripe-for-staining paper. Same with the paints.

J.
Received on Sat Apr 3 03:14:20 2004