From: Katharine Thayer (kthayer@pacifier.com)
Date: 07/04/03-03:55:13 AM Z
Joe Smigiel wrote:
>
> Chris & Katherine,
>
> I think what is being demonstrated here may be underexposure (or speed) of the Na & K flavors rather than any dichromate stain. The fact that numbers and letters remain with the ammonium exposure indicates that a chromium image, not a non-image stain, has resulted using that salt. A "stain" IMO would be a general overall fog and not an image as >you describe here.
Hi Joe, Chris and all,
Sorry for being a bit behind, but I've been away and not following very
closely.
I can see Joe's point that the term "stain" may not be a good term to
refer to an image that's made of chromium deposits. I've used the word
"stain" in the past to mean something that doesn't belong in the print
and can (and should) be removed, which in most cases is true of chromium
deposits in a gum print, whether the deposits form an image or an
overall tone. It's never been part of my definition of "stain" that the
stain has to cover the whole image. A spot on the front of a blouse is
a stain, even if the entire fabric isn't affected in the same way. To
me it's stubbornness that defines a stain, not coverage. But if others
understand "stain" to mean something similar to "fog" then perhaps I
need to find another word.
The term "stain" has been tossed around in past discussions to refer to
pigment stain, to simple overexposure, to residual hexavalent chromium
(yellow) that doesn't wash out in the water bath (this happens with some
combinations of paper and size, I've found), and to deposits of
trivalent chromium that may form an image or may form an overall heavy
stain on the paper, depending on the extent of overexposure. In the
process, different issues have gotten confused, I think, and so I agree
with Joe that we probably need different terms for these different kinds
of "stain."
For example, Chris had a discussion a while back about pigment stain,
trying to get to the bottom of what causes pigment stain. In her
discussion, (I hope I'm remembering this right) she listed one of the
"causes" of pigment stain as "overexposure" with the solution being
longer development. To me, an overexposed image that can be resolved by
leaving it in water is simply an overexposed image that can be resolved
by leaving it in water, it is not an example of pigment stain. Pigment
stain (IMO) is when the pigment has penetrated the paper in such a way
that the stain is permanent and can't be removed by any length of
development or any other remedy known to man; the print simply has to be
tossed out. This kind of pigment stain, which is the only kind for which
I think the term is appropriate, has its cause in the gum/pigment ratio
and/or in the paper/sizing combination IME.
In the present example, the reason I called the image created by
chromium deposits a "stain" was that I understood Chris to say that the
image remained even after clearing in metabisulfite. Her clarification
that clearing in metabisulfite erased all the steps and numbers changes
my understanding, but I think the discussion about terminology is still
useful; in order to have meaningful discussions about practice, we need
to be able to agree on the definition of basic terms, and I'm afraid
we're not even there yet.
Katharine Thayer
> > Hi Keith,
> > One thing I did today, too was to do side by side exposures of am,
> > pot
> > and sod di to see if there was a speed dif. I swear, am di is really
> > fast! It gives the clearest, sharpest steps of all three dichromates, is
> > the speediest, and sod is not much different than pot. I did this test
> > with NO pigment, just side by side straight dichromate. Then I cleared
> > to see what remained, and the am di was the only one that printed the
> > numbers and the words and the steps of the tablet.
>
> Hi Chris and all,
> I think what you're demonstrating here isn't how the three dichromates
> print in normal gum printing so much as you're providing support for the
> idea that ammonium dichromate "stains" (meaning dichromate staining, not
> pigment staining) more than the other dichromates, which I haven't
> observed myself but others have reported. If there's no pigment in the
> coating and you still see the numbers, words, and steps of the tablet
> after the print has been cleared, then you've got dichromate stain, which
> in my experience generally results from overexposure.It may be that people
> want to print with dichromate stain rather than with pigment, as in your
> historical example, but we should be clear that that's something different
> from the usual printing practice.
> kt
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