From: Judy Seigel (jseigel@panix.com)
Date: 02/08/02-03:54:01 AM Z
For folks with some interest in the pigment stain question, this & a
couple more I'll send tomorrow (well it is tomorrow, but you know what I
mean), have got what may be some new info, and come to about what I
can/will/should say on the topic. For those not interested, delete
instantly.
J.
===============================================================
A funny thing happened on the way to this umpteenth "explanation" about
pigment stain. I noticed what I should have noticed long ago. And that is,
as far as I can tell, Paul Anderson *invented* pigment stain. He got it
from bad habits, then found a "cure" as bad as the disease -- and, such is
the nature of "art" photography and the zeitgeist that this debilitating
error remains a centerpiece of OUR gum literature, 72 years later.
This flash of understanding arrived with incredible sloth, of which I do
not boast. But ultimately, I checked the gum chapters & articles in a
congeries of books, pamphlets, magazines, annuals, manuals, formularies,
dictionaries & encyclopedias back to 1896 (and invite whoever has any
available to do likewise). I can't say I found *nothing,* but I found
*almost* nothing. That is, in dozens of sources, only one even mentioned
"pigment stain" before Anderson. That was Cassell, in 1911: "The paper
must be well sized, in order that the pigment may lie on the surface and
not sink into the substance of the paper so as to stain and degrade the
high lights." Honesty compels me to admit I did not check every single
volume of every single annual (and of course there are many gaps on the
shelf), but most "process" entries remain unchanged for a decade, so I
figure 5-year intervals covers it. Judging by the quality of their other
observation, I don't think folks would have failed to notice pigment stain
if they'd had it. (But if someone finds a stain alert or lament I missed,
please send word.)
Meanwhile, I re-read Anderson: Now it leapt out -- he's using almost ONE
HUNDRED PERCENT sodium dichromate solution for sensitizer. He mentions
potassium dichromate at 10%, but "prefers" sodium dichromate, 960 grams in
1000 cc, because it's "quicker." ON TOP OF WHICH, he uses two parts of
this Extreme Sensitizer to one part gum. In Henney & Dudley, it's even
more, 35 cc dichromate to 15 cc gum. On top of which, he likes unsized
paper. Is it any wonder the man had pigment stain? (His TEETH should have
pigment stain.)
Before, during, and after Anderson, the most usual dichromate was 10%
potassium, most often in equal parts with gum. Even today I know of nobody
using stronger than 30% am di. The ratio of gum to sensitizer varies, from
equal parts, to 1 to 3, or 3 to 1. But, since the dichromate controls the
stain (as I shall explain, be patient), Anderson had a problem. Did
anybody else? Not that they mentioned. (I've taught or helped, done
trouble shooting with, gotten calls or e-mails from a lot of printers &
students, not ONE of whom arrived saying, "Oh woe, I cannot get rid of
this pigment stain." And no case of staining I ever saw wasn't fixed by
recoating the bad size, changing the paper or gum arabic, giving up the
anorexic negative, abandoning the hair dryer, or losing the cheapo student
watercolors. Lowering pigment was beside the point.)
I admit I have said on every possible occasion (to small thanks) that the
dichromate is part of the equation. Actually, it *controls* the equation.
But did you ever wonder why none of the legions dutifully working up this
gum pigment ratio thing, dram by dram (one dram = 3.5 cc), with such
"scientific" care and keen observation ever noticed that adding the
sensitizer cancels out everything they've spent those long hours
precision-testing?
It seems one person did: William Crawford ! In "Keepers of Light" he says,
"The dilution of the pigment/gum mixture by the sensitizer actually has no
effect on the staining." Actually, he's whistling in the dark. "What is
important," he says, "is the relationship between a specific amount of
pigment and a specific amount of stock solution." And he wishes us to
believe that these smart pigment particles know which water molecules came
in with the gum and which came in with the sensitizer, so they can have a
proper relationship !? I don't think so. Scopick recently told this list,
as proof of the excellence of the G-P-R test, that his students never had
any trouble with it. Truth to tell, I also failed to pick up on the
nonsense just quoted until I was experienced enough to recognize
gum-o-babble when I saw it.
I suppose some folks reading this will still demur. So under separate
cover I outline a few simple tests for proof. Meanwhile, I note two
bizarre phenomena that shed more light on the process. First, am I the
only one who has made a test strip with some weirdo brand of watercolor
that likes to stain and found that whites cleared up to step 10 or so,
then began a reverse scale, building tones IN PIGMENT STAIN, in nice stair
steps, but now in reverse, lightest at step #11, darkest at the top? At
first I suspected a light leak, then realized that, being so consistent,
it had to be the material itself. I asked the list, under some subject
line like "Gum Mystery," probably in early 1995. No answer.
Then a similar, even stranger effect -- a 21-step with tone up to step 4,
then perfectly clear whites in steps 5 through 9, then HEAVY staining in
steps 10 through 21. Not possible? It's in Post-Factory #3, page 38.
Finally, Mike Ware (who was on the list in '95) offered a plausible
theory: Pigment stain occurs when the emulsion isn't viscous enough to
stay on the surface of the paper, but soaks at least partway into it,
where it is hardened by the dichromate (as may happen even without
"exposure"). In fact, any concentration of pigment can sink into the paper
& be held there, if other conditions are right. In this case, steps up to
#9 got sufficient exposure to become viscous enough to NOT soak in, the
ones after that (higher numbers) didn't.
Which is to say, exposure is part of the equation. AND so is the
dichromate. The hardening happens at or just under the surface of the
paper, where there is relatively more dichromate, probably because it
soaks in more than the fuller-bodied ingredients. (Anderson's diagram
showing unhardened emulsion oozing out through the hardened surface is
almost certainly also wrong. If there were unhardened emulsion under a
crust, the crust would most likely flake off.)
I did some cute little prints in that reverse-step technique --
"direct-positive gums." (also in P-F #3, p. 38.) But it takes a really
dense negative, a strong stainer, and long exposure. Here's a simpler way
to prove the point about viscosity and stain. Coat two test strips with
any gum-dichromate-pigment combo that's not a big stainer, but give the
mix for one of the strips twice the pigment of the other -- gum and
sensitizer in the same amounts, only the paint is increased. Expose &
develop. Odds are, the strip with twice the pigment will stain less. The
extra pigment makes the emulsion more viscous, so it doesn't sink into the
paper. (Of course, if you double pigment in a combo that stains to begin
with, you may expect double the stain; but the *relative* stain is no
greater.)
I had by then figured out, & Mike Ware confirmed, that "the usual stain
test to get a pigment-to-gum ratio as described in the books is
[essentially] meaningless," since it does not duplicate conditions of the
actual event. And, as noted, adding dichromate to pigment-in-gum may cause
stain just by being there. (I feel a certain discomfort quoting Mike Ware
in this, invoking the holy name, as it were, but failing to implies I
thought of things on my own that I'd had no clue about. I note also that,
onlist and off, he distinguished between what he knew and what he
hypothesized. I have added a few extensions and interpretations, however,
for which he is not responsible.)
Meanwhile, Pete, who at last report claimed to still believe in the G-P-R,
has cited the "masterly work" of, among others, Joe Smigiel. Here's Joe,
writing to the list, August 18, 1998, subject line "Gum Print Questions,"
QUOTE: "I suspect [there are] many people out there who have simply given
up on gum when it didn't work as explained in the popular texts. If I had
not seen some of Steichen's work in person, I might have been among that
group. My earliest experience was frustrating..." Demonstrations seemed to
all be high-contrast lith negs and poster effects. Now, that "high
contrast poster look seems more prevalent, just as the stain test
persists..."
Step One in his technique, Joe said, is "mix as much pigment into the
emulsion as you can without causing flaking." Step 2, "Use about twice as
much gum as sensitizer."
cheers,
Judy
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