From: Judy Seigel (jseigel@panix.com)
Date: 04/17/00-09:04:31 PM Z
On Mon, 17 Apr 2000, Sarah Van Keuren wrote:
> 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
All I can say is come visit & I'll show you the test strips -- this from
memory because my NuArc is on the fritz (apologies to any Fritzes onlist)
-- but my usual exposure for cyanotype was 400 units, for VDB depending on
negative was 200 for very thin, 400 normal, to 600 units for very dense.
The blacklight fluorescents which I use now I'm going to fudge a little
since I haven't done much cyano since the change -- but at 3 inches from
the bulb they were about 10 minutes "normal", up to 15 minutes for a
bulletproof glass place with very old emulsion. I also remember that my
first tests with cyano using just 4 BL fluorescents before I had the
vaunted NuArc were standardized at 10 minutes...
At school, I'd say average exposure by students was from 10 to 15 minutes,
depending on paper & neg -- which brings me to a thought that occurs to me
as I write: I do not print cyano on heavy artsy paper. I like the elegant
detail of smooth light paper...one-ply bristol or the like. I haven't made
a serious study of it, but I have the sense that a thin paper is faster
than one of those blottery ones where the emulsion sinks in. And some
papers (perhaps relatively alkaline ones) are VERY slow.
I'll also ask neighbor, famed cyano printer, what his times of exposure
are -- but my recollection is that they're circa 10 minutes, too. Hey --
another thought -- what KIND of BL fluorescents is anyone talking about?
The BLB emits much less light (that blue glass keeps most rays IN), and I
know from experience is about 1/3 slower. That couldn't account for the
entire discrepancy, but.... maybe the little things are adding up.
My formula was the classic 20 g fe am cit/100 cc distilled and 8 g K ferri
/100 cc distilled. If you're using tap water, needless to say, that also
can make exposure very slow...
> ....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
In the beginning I did use sun for cyano, don't remember the times -- but
getting no more than 1 hour of sun a day in my city backyard, &
inconvenience of exposing outside the studio, so I had to sit and watch
the grass grow, as it were, during exposure, cured me of any desires along
those lines... I did notice, incidentally by loupe, a *delicacy* of image
from the sun lacking by fluorescent, explainable as the difference of the
*point* light source. But since I only detected it by loupe, I stifled my
grief.
As for the speed -- well, sun is after all 93 million miles away, my
fluorescents only 3 inches.
best,
Judy
> 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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