BFK Rives & UV sensitive processes

Kevin Crombie (kcrombie@montreal.com)
Mon, 16 Dec 1996 19:16:32 -0400

Dear all,
I know that it has been mentioned here before, because somewhere in
the darker recesses of my (evidently) tiny mind I can now dimly recall it
coming up in passing. But after a frustrating weekend spent repeatedly
emptying my hot water heater and ruining dozens sheets of paper, I feel it
bears repeating: BFK Rives engraving paper is lousy for alternative
processes that rely on UV light, artificial or otherwise.
Do not be attracted, as I was, by the bright, white smooth finish
of the velin paper -- it apparently contains a UV brightener, a chemical
which will fluoresce in the presence of UV light, making it appear brighter
& whiter. And completely screwing up any chemical reaction you hope to take
place in the sensitizer you have lovingly and carefully brushed onto its
surface.
One other observation, based on this weekend's debacle:
Unexposed cyanotype chemistry is apparently very sensitive to heat.
My new, primitive lightbox was taking up to two hours to expose prints,
until I stuck a fan nearby to cool the tubes. Exposure times dropped to
20-30 minutes. Apparently the glass of the contact printer would become hot
enough to cause a reaction on the surface of the chemistry, creating a thin
mask of very dark chemistry. This would make it difficult for the light to
penetrate to the chemistry underneath and create an image. I have actually
experienced this same problem in the full light of the sun, but attributed
it to some other incompetance on my part.
Cyanotype chemistry is also very sensitive to humidity, but that's
another story. In the dry, cold, terrible winter, I can coat paper days
before I use it. But in the summer, the unbearable humidity of the Montreal
summer will cause it to react even locked away in the dark, creating
strange stains on the images. This I learned from another weekend debacle,
trying to get stuff ready hours before a vernissage...
Kevin

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Kevin Crombie e-mail: kcrombie@montreal.com
387 rue Villeneuve est voice: (514) 849-7601
Montreal, P.Q. H2T 1M1