From: Fred P. Arnold (fparnold@balihai.uchicago.edu)
Date: 05/10/00-07:51:59 AM Z
William, etc,
The acid, while potentially bad for the paper, is a boon to the prussian
blue which fades in alkaline environments. Here in the Hyde Park
neighborhood of Chicago my water (minimally treated from Lake Michigan) is
alkaline enough to bleach the highlights of either the Ware cyanotype or
traditional if I use it for the wash. This has forced the use of
distilled water for the wash, which has caused no problems.
Thanks to all for the suggestions a while back concerning bringing
cyanotype under control. I've been getting an excellent blue and
reasonable contrast range using the traditional formula with slightly less
Solution B (ferricyanide) and a Rives printmaking paper. (purchased due to
the moodiness of the new process). I've actually been able to get away
with single coating since that paper has a bit of a 'tooth' to it and
seems to hold more solution (or hold onto the Prussian Blue afterwards).
A few drops of dichromate and my harder negatives print with a full tonal
range without making enhanced contrast copies. As is always mentioned,
it prints well on heavy cotton as well, though I haven't found a picture
that the weave really enhances yet; more of a proof of concept so far.
One question about the acid bath: if I use dilute HCl in the initial wash
water I tend to get veiled highlights, though complete clearing and a good
maximum density. If I use just distilled water I can get white
highlights, and then darken the blue (apparently) by using a final quick
rinse in the acid. Would my bath be too strong, wrong paper, or what?
The paper is coated by foam brush and allowed to air-dry in the dark, then
exposed using a BLB tube. Exposures run about 25 minutes for a 4x5.
"No science has ever made Frederick P. Arnold, Jr.
more rapid progress in a A&HPRC, U. of Chicago
shorter time than Chemistry." 5640 S. Ellis Ave
-Martin Heinrich Kloproth, 1791 Chicago, IL 60637
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