From: Gwen Walstrand (gwalstra@lib.drury.edu)
Date: 04/17/00-02:32:38 PM Z
Sarah and Judy,
Thanks! This is helping tremendously in figuring out this problem.
Today in class, a student brought in eight or ten cyanotypes she made with
sun exposure in about 15 to 20 minutes each. This is the same solution that
we use with the UV light source (metal halide) which takes about one hour
to expose properly. Perhaps the bulb is dimming with age? We use the
traditional formula that is listed in Bea Nettles book. Our light source
works wonderfully for all the other processes and is a replacement for an
old flourescent tube system that seemed to cause so much waiting.
The paper we use varies, but our best results are on Stonehenge and Arches
papers. I'll test some others.
Judy, I'm curious what recipe you use for cyanotype? And what light source?
Sounds like the sun is hard to beat.
Gwen
> Judy wrote: But exposure times for VDB & cyanotype are, with any
>lighting system I've
>used, within 20% of each other. Maybe you've got some cockamamie paper?
>Try a test of the cyano on a good quality typing paper, or even a paper
>bag, to check that..
>
>Judy, I can't believe that you have found vandyke brown and cyanotype
>exposure times to be within 20% of each other. My experience has been more
>like Gwen's, though not quite so severe. To achieve a cyanotype exposure
>as rich as a full-bodied vandyke takes an exposure that is at least 3 or 4
>times as long as for the brownprint. I use the most commonly published
>cyanotype formula first found in Bea Nettle's Breaking the Rules: 50gr
>ferric ammonium citrate to 8 oz. distilled water for A Sol., 35gr
>potassium ferricyanide to 8 oz. distilled water for B Sol. (I'm sorry to
>mix avoirdupois & metric but that is how it was transmitted.) Perhaps your
>formula is faster without being Mike Ware's New Cyanotype formula. I
>noticed that my formula was not given in his book, Cyanotype, though he
>listed many old ones. I am intrigued by the idea of increasing the amount
>of A Sol. and will try it in the sun this summer. Perhaps my pinhole
>negatives that range from almost clear to very dense require longer
>exposure times than your negatives but still the proportion between the
>times for vandyke and cyanotype would remain the same. Maybe light source
>is the clue. Perhaps vandyke and cyanotype are sensitive to slightly
>different wavelengths within the realm of actinic light and maybe you are
>using a light source, such as black light, that is fast with cyanotype but
>slower with vandyke. I am basing my comments on observations made during
>over twenty years of sunprinting and also using various platemakers. I
>don't even bother using my sunlamps for cyanotype.... In the sun, middle
>of day, a strong cyanotype only takes about 10 minutes even with my
>negatives but that could easily translate to an hour with a slow exposure
>unit like Gwen's.
>
>Sarah Van Keuren
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