From: Richard Sullivan (richsul@earthlink.net)
Date: 08/02/03-10:35:14 AM Z
At 11:24 AM 8/2/2003 -0500, you wrote:
><Dick said>One need not overly
> > complicate the gum process and get all tangled up in the issue of pigment
> > staining.
>
>Dick,
> I think Clay's talking about dark reaction, not pigment stain.
>Certainly sizing would take care of any pigment stain, but if you DON'T want
>to size (like some of us, and like many of the gum printers today and of
>old) this is more of an issue.
I wandered into the stain issue and didn't mean to relate it to the dark
reaction.
Ok you then agree that pigment stain is a function of sizing?
Why not size? When one considers the work one goes to to make a gum print a
bit more time to size the paper seems to be well worth it. No one I know of
makes gums because they're easy, or do they?
> > I too have my treasured copy of Kosar and have noted the section that
>talks
> > about incompatible pigments with chromium. The main one was is
>ultramarine.
I'll check my copy. I was going on memory and I may have not have got the
source correct. I made copies of several sources cited in Kosar at the UCLA
chem library and it may be in a cited reference. I do definitely recall
seeing ultramarine as an incompatible color with chromium.
I am sure you have read Bright Earth as you seem to be quite up on your
sources.
How do people keep neat?
--Dick
>What page is the ultramarine or chromium comment on? What edition? I have
>not run across that pigment name mentioned, and am interested if it is
>because when I mix this color into gum it gives off a really smelly smell.
>However, it still works fine, and without staining, although I find it a
>weaker color as you have, below. Kosar mentions the comment about pigment
>incompatibility but doesn't say which are incompatible, not even chromium.
>Scopick repeats this statement about chromium pigments and sources Blacklow.
>Blacklow doesn't source. So I am curious.
I will try to find my reference but don't hold your breathe. We bought a
second building for the carbonworks and we were so crowded over here that a
lot of my stuff got transferred before the office was finished and a lot of
my books are boxed up in a corner of the reception room.
>Chris
>
> > Despite Kosars references I did not see any degradation of ultramarine
>with
> > chromium in carbon printing. It is quite transparent compared to thalo and
> > uses up a ton of pigment, an issue when you are coating 75 sq feet at a
>time.
> >
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