Re: Scanning pigment stain

Hey, here's a great argument for using Anderson's most excellent dot test.
Since the concentration of pigment (phthalo blue) can vary dramatically from
manufacturer to manufacturer, why not use a scientific and highly accurate
means of calculating pigment concentration and staining ability? Ever spill
a 97% mix of pure phthalocyanine blue pigment on the upper extremities of a
black swan's wing? Ugly, man. Really ugly!

Anxiously awaiting that 299th response.

Best regards from Big Wonderful Wyoming,
Dave Rose

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, April 23, 2004 9:21 AM
Subject: 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
> _______________________________________________________________________
>
> 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.
> ______________________________________________________________________
>
> 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...
> _____________________________________________________________________
>
> 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 Mon Apr 26 01:18:40 2004