From: Robert W. Schramm (schrammrus@hotmail.com)
Date: 04/18/00-05:12:41 PM Z
I have to go with Judy on the exposure times for cyano and VDB. My
experience, using the same negative, has been that they are very similar
(not exactly the same). I am using a flourescent exposure unit
with BL bulbs. The print frame is about 1 inch from the bulbs.
Bob Schramm
>From: Judy Seigel <jseigel@panix.com>
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: Alt Photo <alt-photo-process-l@sask.usask.ca>
>Subject: Re: cyanotype sensitivity
>Date: Mon, 17 Apr 2000 23:04:31 -0400 (EDT)
>
>
>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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