From: Christina Z. Anderson (zphoto@montana.net)
Date: 02/12/03-10:08:40 AM Z
Finally, I've found out the source for the UV inhibitors in paper negs!!
Erich Camerling wrote me off list, the following answer, and saved me a
bunch of time looking up paper negs in books. So now, back to Martino's 5
day exposure, below. First of all, Martino, where do you live--like at what
latitude? 5 days seems an awful long time, and your image looks like it
still is underexposed. Or else the paper is unsuitable and you have
bleeding out of the cyanotype, or you washed it too long. And, if Katherine
is having exposures with paper negs that are not too much different than her
regular negs, with gum printing anyway, I'm wondering what is going on.
Hey, I've got an old paper neg, I'll print today or tomorrow and see if my
times are that outrageous. I'm pretty far north, too, in Montana, but I am
at UV rich 5000 feet. I've just used up all my Ware's solution and have to
mix the traditional cyanotype stuff up first, which I was going to do
anyway. Are you using traditional or Ware's cyanotype? The traditional is
slower, unless you mix it 2 parts A to 1 B as Sam Wang does, and he says his
times approach the Ware formula.
Shannon (sorry to condense two posts into one here) the "conversion"
thing that I was talking about was a curves and channels thing that you do
to an image to make it into a suitable negative for cyanotype printing. Sam
prints the red channel only for cyanotype, but he applies this curve to it
first.
Chris
<from Erich Camerling about paper negatives on RC>
"Baryta coated (fibre-based) papers (like Ilford Multigrade FB etc.)have an
anti-stress layer an emulsion layer and a Baryta (Barium sulphate mixed
with an adhesive) coating on a paper base RC (polyethylene-coated) papers
have an anti-stress layer an emulsion layer a pigmented polyethylene layer a
paper base a clear polyethylene layer and a back-writing layer. You cannot
peel off the paper base from the baryta-coated papers.
But with RC-paper you can peel off the very thin anti-stress + emulsion +
pigmented polyethylene layer. (When you scour the back-side of the dry
paper-negative carefully with abrasive paper (~no.400) you can remove all
the paper remnants and have a good neg for visible-light-sensitive
processes. But for UV-light-sensitive processes (based on UV-light-sensitive
iron salts) like Platinotype.Cyanotype and VBD(or kallitype or argyrotype)
you cannot use a paper-negative in practice because of the UV-blockers in
the layers. I never used paper-negs in the enlarger,only in
contact-printing. An enlarger doesn't give UV-light,so even hours of
exposure will not give any result for UV-based processes." Erich
<from Martin Reis>
> Here is a test sample of a cyano made from an RC paper neg. Originally a
> Kodachrome slide printed onto RC B&W paper, peeled and oiled. Printed onto
> sized 100% cotton rag paper. Exposure time was 5 days.
> http://www.web.net/~lukmar/images/blue1.jpg
> Still working on this one, obviously, and I am posting this just for
general
> interest.
>
> Martino
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