Re: muddy gum print--help?
Charles,
Generally, the closer a paint at mass tone is in value to white, the
more opaque it will be. So, most yellows will be almost as opaque as
white while most darker violets and blues will be largely
transparent. The most transparent pigments should go on last OTBE.
Therefore, a general rule is to layer the sequence in order YMC. Of
course, when visually registering negatives, it is difficult to see
the completed yellow layer under another coat heavily colored by
orange dichromate, so many would alter the sequence by putting down a
pthalo blue or cyanotype layer first to aid later registration. I
personally would still avoid printing most yellows last.
I think your magenta is staining.
If you print and process a sensitized but unpigmented gum layer
first, it will act as a size without the need to harden with VOCs.
Joe
On Apr 12, 2009, at 3:32 PM, Charles Ryberg wrote:
Folks:
Thanks for your help. I'll reprint Monday (as I mentioned
yesterday I stupidly ruined the example I posted).
Does the order of printing matter? The example was Cyan, Magenta,
Yellow.
I can't size--asthma keeps me away from VOC's and my urban loft
provides no back yard or garage with fan.
I use Fabriano Artistico Hot Pressed--it seems to stain less than
Arches.
My Lukas Process Magenta (PG2) does stain, though not as much as
some of the other magenta/reds I have tried. My Daniel Smith Hansa
Yellow Medium (PY3) stains too. The Daniel Smith French
Ultramarine (PB29) stains very little.
I did a curve for each pigment at a concentration which seemed to
me to be the most pigment I could use. Prints made with those
concentrations and curves were even worse than the one I posted.
Trial and error led me to pigment concentrations of about 70% of
maximum and exposure time of about 80% of what I had determined
“scientifically.” I suppose I could post the curves if you think
it would be helpful. I use potassium dichromate on the cyan and
magenta, ammonium on the yellow due to excessively long times with
yellow and potassium.
Exposure is BL tubes. Timer is GraLab. Registration pins by Pro
Art (that's supposed to be a joke).
Any help before I reprint (a better magenta? a different
printing order?) would be welcomed.
Any help after I reprint, of course will be also welcomed.
Charles Portland, Oregon