From: Judy Seigel (jseigel@panix.com)
Date: 03/21/03-12:31:45 AM Z
On Thu, 20 Mar 2003, Christina Z. Anderson wrote:
> > I doubt acidity of gum is a factor in staining... unless you mean less
> > acid more staining, because the Pictorialists often recommended letting
> > the gum sour... I myself found no correlation of any factors with
> > "acidity" of gum, although admittedly my acid-ometer was subnormal.
> >
> Wouldn't sour gum be more acid?
Yes... my thought was that since they wanted it sour, maybe sour stained
less... tho who knows why they liked it sour, maybe it was the smell...
and from what I've seen of "the literature" staining was not considered a
great problem til Anderson. True, I missed your Demachy reference -- tho
in 3 or 4 other Demachy treatises little or no mention of stain.
> Alkalinity in the form of ammonia held back exposure. Acidity in the form
> of lemon juice increased the sensitivity of the emulsion. No, I meant that
> the more acid the gum was the faster the exposure would be timewise, so that
> you would not get clearing of the highlights--overexposure, which you will
> now point out :), is not staining in truth but provides for unclear whites.
As noted, I didn't find connection between acid gum & speed... tho my
impression from the "literature" is that they weren't particularly
concerned with "speed" then anyway...
> No, what you were backwards on is the particle size (see below) and the term
> staining colors, as per below. Staining colors are smaller particled and
> synthetic. But whether the color actually stains in gum printing is
> different, of course as you say or we practice, since we combine it with gum
> arabic. The only thing I will do in practice knowing which colors are
> staining vs. non staining is make sure I have enough gum arabic to prevent
> the staining from occurring and use less pigment anyway, which you can
> certainly do because the colors are intense. The fact that a color is
> smaller particle sized and would stain fits in with what you said a while
> back on the list that some brands of tube paints are too finely ground and
> stain.
I didn't say anything about too finely ground and staining -- I said some
brands or colors within brands have such things as dispersal agents which
can cause staining...
Whatever & however -- perhaps the lady from Winsor Newton had it wrong...
but she definitely said the organic were larger & irregular particles and
therefore "staining" because their odd shapes would get stuck in the paper
fibers.
However I had a thought about why your findings re staining might be so
different from mine -- are you doing those tests on Rives BFK?? That's a
lovely paper and mostly what I started students with, but, especially
unsized, it can act weird and different. I don't use it for prints any
more because it's a bit rough for my preference and thin for large prints,
but I have a bunch of it around and when I'm testing something or other,
it's almost no extra trouble to do a bunch at one time, use up the
emulsion & maybe get extra info on several papers. BFK unsized can do a
lovely print, but it can also stain like crazy... at least with some gums.
> Also, I find that bringing in other authorities from other disciplines
> such as Page (who obviously spends her life researching paints) whether she
> gum prints or not (presumably not) may enrich our understanding of what we
> do, a sort of thinking outside the box.
Amazon Dot Com doesn't like my computer -- told me my "authorization" was
expired... but a friend has ordered that book for me. Thanks for the
suggestion !
> Furthermore, Kosar's use of mild disclaimers is no different than
> others on this list (including you and me) in essence saying YRMV--your
> results may vary. (As an aside, one of the teachers I work with the
> students call him a "walking disclaimer".)
You are very kind -- mild disclaimers indeed ! He cites OTHER stuff and
then extrapolates... more like a Walking Extrapolator, which may be
dangerous, even possibly illegal.
> Also, to address another post, to clarify, I sensitized a piece of paper
> with dichromate mixed with gum arabic and let that DRY. Then I applied
> powdered PIGMENT to the surface, which should be done by BRUSH. I don't
> find that that would be harmful anymore than handling a sheet of dry
> dichromate paper in the first place. I hope you did not think I was
> brushing on dry dichromate powder (?)
Chris, I didn't imagine THAT degree of depravity, but I thought you might
be sanding and rubbing a surface with dichromate, which would make
dichromate dust, which is very distinctly to avoid. I wouldn't suggest
using dry pigment either without a dust mask -- though hmmmmm... that
sounds intriguing. Tell us again -- how did it work?
J.
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