Re: (1) Gum over Cyanotype on sized Masa paper (rough side) - (2)Pigment that makes gum insoluble w/o exposure?
Loris, thanks for sharing this. Just a couple of thoughts:
Transparent colors should give you a neutral color balance just as
easily as opaque ones, if not moreso, because there's a clean mix of
the colors overlaying. It's hard to tell from the screen, but I
would have said your print has a blue-green cast. More PV19 should
neutralize that; did you try printing with a little deeper
concentration of that? Transparent doesn't mean wimpy, as my website
comparisons of transparent vs opaque pigments demonstrate.
Thanks for correcting the name of the pigment; I had noticed but
didn't want to make a point of it.
I'm glad you went to the source and got the right name.
You're doing great, and thanks again for sharing. Pictures worth
many many words, as you know.
Katharine
On Sep 24, 2007, at 11:13 PM, Loris Medici wrote:
See my last gum over cyanotype print on sized Masa (rough side) below:
Full image (actual size 17 x 27cm, 6 5/8 x 10 5/8"):
http://www.loris.medici.name/gum/gum_over_cyano_02_sm.jpg
Detail (actual size 4.5 x 5cm, 1 6/8 x2"):
http://www.loris.medici.name/gum/gum_over_cyano_02_crop.jpg
Diagram:
http://www.loris.medici.name/gum/gum_over_cyano_02_diagram.jpg
Image on unsized Masa (rough side):
http://www.loris.medici.name/gum/gum_over_cyanotype_01_sm.jpg
As you can see the result is much much better despite it's hard to
make
a direct comparison since:
a) I have used transparent pigments (hoping to get less muddy results)
b) I have used 1:1 diluted 2A:1B traditional cyanotype (because
undiluted is too dark for making gum overcoats I thought)
In the second print (on sized paper). In any case, the difference in
whites is obvious. Sizing and using the back side is the key to
success
with this paper...
As you notice, I'm trying primary (or quasi primary) colors with this
print, because I also aim to learn how different primaries interact.
Will try to use darker and/or more opaque paints (or more pigment with
the same paints) in the next try since I was expecting a more neutral
final image color...
About red: Mine is "gamma quinacridone" (according to:
http://www.handprint.com/HP/WCL/waterc.html#PV19R). It's a very strong
pigment, I succeeded by cutting the pigment amnt. and exposure time
considerably.
Layer info:
1. 1:1 diluted 2A:1B traditional cyanotype, 4:00
2. Schmincke Cadmium Yellow Light 224 (PY35), pigment load: light,
4:00
3. Schmincke Ruby Red 351 (PV19), pigment load: very light, 1:45
(All layers with the same negative calibrated for 2A:1B traditional
cyanotype.)
BTW, the creasing you see was caused by me being clumsy while affixing
the paper to Yupo. I would normally discard the paper and re-make
but I
thought it suits the subject matter and pursued. The effect is not
that
strong, it's exaggerated by the scanner -> you can't see it unless you
look the image in strong and very oblique light...
Regards,
Loris.
-----Original Message-----
From: Christina Z. Anderson [mailto:zphoto@montana.net]
Sent: Monday, September 24, 2007 5:52 PM
To: alt-photo-process-l@usask.ca
Subject: Re: (1) Gum over Cyanotype on sized Masa paper (rough side) -
(2) Pigment that makes gum insoluble w/o exposure?
Loris,
I'm so glad you experimented with MASA as per Rajul's advice--makes me
want
to try it now that two of you have found it to be suitable.
I have never had a pigment insolubilize gum, but after reading Marek's
question with the one pigment and carbon it makes me wonder something.
A
bit ago I had mentioned the fact that formaldehyde hardens gelatin but
not
gum and that is why it can be used as a preservative in gum solutions.
I
wonder, therefore, if carbon is more sensitive to this kind of
happening
than gum is, and if some of these feelings of spontaneous hardening
were
a
holdover from carbon, and gum being associated with carbon as a
"direct
carbon" process as it was first called. I was explained the
difference
between the two--chemists please correct me but gum is composed of
carboxyl
(sp?) groups and gelatin of amino acid chains? So that might explain
some
differences in results between the two substances--they are
colloids but
not
the same colloid.
The very FIRST mention of spontaneous insolubilization was 1894!! In
the
very first gum book ever written!! Rouille Ladeveze. Blanc d'argent.
If
anyone in France can locate me some blanc d'argent I'd love to test
it.
So
even though I say I have never seen this I cannot say that it doesn't
happen.
Anyway, on to red. I have never had a red spontaneously harden, but I
have
found that students will tend to confuse two things--stain and
overexposure.
I have no idea if either of these are your case.
Two, is the ruby red a blue red? Offlist I got a question from
Michael
Koch-Schulte about whether I had found reds to be faster than other
colors
and no I had not, but I did determine a difference in exposure
between a
blue red and an orange red. In fact, if I am not careful to expose
the
orange red much longer (certain ones, btw) it'll all whoosh off.
These
are
with pretty dense layers, like the color of the layer looks as colored
as
the pigment itself.
It would be instructive for us to share what we have all found related
to
exposure times of different colors. Old literature says blue is the
fastest
exposing and I have certainly found that to be true, and yellow
slowest,
but
then I wonder if the difference of exposure times is directly
related to
the
amount of pigment one uses and that will explain the variations we are
all
finding--for instance, if I am just using a little pigment in my
mix of
any
color, maybe there is not much of a difference in exposure between all
colors, but if I am using a LOT of any color with supersaturated
layers,
that's when the noticeable difference in exposure time crops up.
And I
am
not just talking the darkness of the pigment affecting exposure time
(e.g.
black is the darkest, or saturated thalo blue as compared to saturated
yellow, for instance). I'm talking actual colors acting as filters to
the
light--and as I said in my Magnachrom article, it stands to reason
that
yellow would be slow by filtering out UV light the best. And this
would
also be a possible explanation to why an orange red biased to yellow
prints
slower than a blue-red biased toward a faster color.
Because there are so many variables that gummists use to make their
prints
(amount of pigment, thickness of layer, whatnot) there probably is no
way we
could build up an agreement about any of this, and I expect 20 emails
shortly refuting anything I have said here, but suffice it to say I
have
never had any red insolubilize gum but I sure have seen overexposure
with it
that gives pretty red squares of image :).
Chris
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