Re: variables in gum (was Re: greens in gum)
My dry green pigments are from Maimeri. Viridian green, which has been
brought to my attention by Christine some time ago, is an easy color to
work with, and not staining at all. Not much covering power either.
Maimeri sells it as 'verde smeraldo' PG18 and it is a hydrated chrome
oxide. BTW it doesn't seem to react with the dichromates at all.
On the other hand, Maimeri phthalocianine green, PG7, stains very very
much, at least in my working conditions. Much more than phthalo blue,
but my blue is from Winsor & Newton so I cannot compare directly.
Phthalocianine green mixed in small quantities with viridian makes a
nice strong covering green.
Judy Seigel wrote:
On Sat, 30 Sep 2006, John Brewer wrote:
I remember reading in a book somewhere that greens are more likely to
stain and should be made from yellow and blue. I've not had a stain
problem with greens. One of those gum old wives tales I guess. Here's
recent gum over cyanotype http://tinyurl.com/ly3bb using DVP 277 sap
green (PG7 and PY 42).
Isn't there another expression besides "old wives tale", something
arguably more politically correct? How about old boys' something or
other... Actually I think there isn't, probably for lack of trying.
(There's an expression something like bubba meisser, but I think that
means old wife too.)
Meanwhile, I agree about green, whoever told the tale. I've found that
thalo green clears as well as thalo blue, which clears as well as
anything I use when other conditions are right, but I usually use the
blue with another color to make green anyway, as it producs a richer
tone. (Tho I have used thalo green for its covering strength, much
greater than for instance viridian, tho I suspect that tubes labeled
viridian may now be thalo... my book giving the specifics has been
stolen by -- I suspect a surreptitious visit from the list... I mean why
else would my Kosar AND my pigment book BOTH disappear around the same
As for the apparently inconclusive considerations of variations of
temperature & humidity and/or relative humidity in gum exposure, let me
suggest that other variables affect the effects as well, which would
explain the lack of consensus. We have in fact agreed that results in
gum printing depend on a *combination* of variables, so it seems
unlikely that exposure/development variables would respond to only two.
My own guess (and extrapolating from casual observation and anecdotal
"evidence") is that developing water, the gum arabic and particular
pigment(s) affect results as they see fit, making "principles" involving
only two conditions in isolation dubious.
Theoretically, one practitioner's results in his/her studio, using same
everything for comparison tests should be more indicative -- but I
wonder how perfect any such tests can be, without true "rocket science"
lab conditions-- at least not in, for instance, urban locations. For
instance (a very small instance, but a good warning) I found that a
particular gum arabic that was unusable in my studio worked fine at
school with same everything (paper & paint) but *Brooklyn* water (or
that was the only variable I could think of -- could have been I suppose
the cigarette smoke in the air).
I've played this game with other printers, exchanging gums & papers &
using paints from same lot, etc., with some totally opposite results
(eg, stained badly vs. cleared, etc.). In my own practice these systems
have less importance, because I don't do a standard development OR
exposure, rather making a ball park exposure time (according to mix,
negative, requirements of print & atmospheric conditions) then
developing ad hoc -- by eye. My feeling also is, how do I know what I
want until I see it? Or, as the extremely old lady said when her
children asked what funeral arrangements she wanted, "Surprise me").
And one other thing... my guess & experience is that even if you suss
out all the variables for your particular set up, some are beyond your
control -- unless you develop in distilled water & maybe even then. At
least here in NYC the water changes by the season, by the weather
(including what sediment the winds stirred up in the Catskills that
week) AND, what the boys in the pumphouse (maybe even a few girls)
decided to add that day. They also vary additives by season... and
(according to the literature in small print they send along with my
water bill) "conditions."