Re: Scanning pigment stain

Christina wrote (I've excerpted just the paragraphs that I specifically
have comments on):

This week I had a hilarious (not really) lesson in staining I thought
I'd share. Personally, there may be a relationship between amount of
pigment
in the mix and staining, but I don't let staining be the controller of
how
much pigment I use, does that make sense? I use a HUGE amount of pigment
in
my mix: 2 tsp of thalo blue, for instance, a tube of it having been
mixed
into 50 ml of gum, plus 2 tsp gum plus 3 tsp water plus 1 tsp saturated
am
di. I would not need this to be any more saturated, pigment-wise
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Hi Chris,
I think this brings up an important source of misunderstanding that
often occurs in discussions about pigment/gum ratios. People often make
the assumption that they use more pigment in their gum than other people
use, with no data to back that assumption up. You say you use a HUGE
amount of pigment in your mix, but the amount of thalo you describe is
about the same amount I mean when I say that because thalo is very
powerful, I use only a small amount to get a saturated tone.

The way I figure your numbers above, you use 3 grams of thalo pigment
(~15 g per 50 ml, x 10 ml=3 grams) per 8 tsp (40 ml) of total emulsion,
or 7.5 % pigment per total emulsion. I can only guess at my numbers,
since I don't measure pigment exactly, but by eyeball it looks like I
use about 1/5 of a tube of thalo, or about 3 grams, in 25 grams gum. I
use 1/2 tsp of this to 1/2 tsp of saturated ammonium dichromate; I don't
add any gum or any water. If I've figured all this right I get a final
percentage of 6% pigment to total coating solution, which given
measurement error in my own eyeball measurements is probably
statistically equal to your 7.5%. (the difference between 6% and 7.5% in
my teaspoon of coating mix is .075 grams of pigment)

Of course no conclusion can be drawn from the fact that we both use
about the same amount of thalo paint; since we're probably using
different brands of paint, (mine is M. Graham) and since each
manufacturer packages their thalo at a different pigment/gum ratio,
comparing our numbers would be very much comparing apples and oranges.
The only point I'm making here is to show that beliefs about amounts of
pigment one uses relative to what others use can be quite mistaken, and
that even very different verbal labels (HUGE vs tiny) can refer to the
very same amount of pigment, so perhaps we can't discuss this issue
intelligently without referring to numbers.
_______________________________________________________________________
(another excerpt from Chris):
Which leads me back to my personal "cause of choice" of staining, that
was back in the old books from 1898: if the pigment is allowed to soak
into
the paper fibers, it will not leave.
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KT: Absolutely; we're in complete agreement here, that pigment stain is
when the color of the pigment permeates the paper fiber and can't be
removed. But I consider that to be the definition of pigment stain, not
its cause.

 It makes me smile to see you refer to Maskell & Demachy 1898, because
after sending my post the other day mentioning this paper, I revised my
page on stain to include a quote from that paper:

http://www.pacifier.com/~kthayer/html/stain.html

_____________________________________________________________________

Chris again:
One black swan may prove that all swans are not white, but it doesn't
prove that there are no white swans--that's the source of argument,
IMHO.
______________________________________________________________________

KT: Exactly. That's all I've been trying to say all along, but perhaps
never managed to put it quite this succinctly. I've certainly never
argued that all the swans are white. I'm quite content allowing for and
accepting the existence of black swans; as anyone who has followed my
arguments on this or any other issue should well know, "each to his own"
has been my slogan from the getgo.

All I've ever said is that my findings support Anderson, Demachy,
Crawford, Scopick and the rest who say that staining is a function of
the proportion of pigment to gum. I've never said that anyone whose
findings or beliefs do not support this idea is wrong, foolish, deluded,
mistaken, or any other of the labels that have been applied to those
whose findings support it.

All I've ever said about those whose observations differ from mine is
that our observations differ. There certainly should be room, in a field
where there are so many unknowns and so many differing observations, for
allowance for honest disagreement between honest workers. That is all
I've ever argued for; in fact I've always said, and still say, that I
don't give a fig about this stupid pigment test. I really don't. I do
care when my colleagues, present and past, are trashed and dishonored
for no good reason, and the times I've spoken up about this, it's been
in response to these labels.
_____________________________________________________________________

Chris says:
this list is SUCH a
wonderful divergence from work...
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This is why I've been mostly unsubscribed lately, because I find it such
a welcome distraction from what I need to be doing that I just have to
make it less available to me; those messages popping into my inbox are
just too tempting to answer. But I'm coming from 24 hours of
discussions with my family about whether my father's prior instructions
about extraordinary measures like a feeding tube apply or don't apply to
the state of drifting consciousness he was in for a while, and against
that kind of reality anything here seems pretty trivial. The problem
resolved itself by my father sitting up this morning and asking for
breakfast, so that's over, but I've been so unsettled by it that it's
hard to settle back down to work, and that's why I've dipped into the
archives again this morning. Carry on,
Katharine Thayer
Received on Fri Apr 23 16:17:41 2004