From: Shannon Stoney (sstoney@pdq.net)
Date: 10/30/02-12:25:03 PM Z
Michael wrote:
>I've been trying my hand at cyanotypes, as a prelude to some albumen paper
>that I am making for use in the next month or so. I am having trouble
>figuring out a couple things.
>
>(1) use of the Stouffer tab and (2) appropriate neg density. BTW, I am not
>using a densitometer, and I am using the sun. I do not and will not have
>access either to a densitometer or to a UV lamp for the foreseeable future.
>(Fortunately I am getting my sun from Arizona not Minnesota.)
I expose cyanotypes in the sun too. I actually prefer it. (But it's
easy to make a UV exposure unit with some shop lights and black light
tubes. Why do it if you're in Arizona though?)
It's kinda hard to make full use of the stouffer tab without a
densitometer. I use the tab to figure out what the highlight density
needs to be, and the densitometer to find out if it is.
Surprisingly, for normal cyanotypes (the classic formula), the
negative does not have to be much denser than a normal silver
negative! My negatives processed for silver work fine, if I process
in plain water, and if I use Crane's platinotype paper.
However, I like a longer scale, so I process in a dilute solution of
water and vinegar, 5:1. This is the first bath only, for one minute;
after that, plain water for nine minutes. That way, I get a longer
scale. And, I have to make a negative that fits this, so I
discovered from the step tab that I have to get the highlights up to
about 1.9. You can find this out quickly with a densitometer, but if
you don't have one, just keep increasing your development time until
the highlights print the way you want them to.
The other great use of the stouffer tab is to figure out whether the
print is "done" or not in the sun. The exposure times will vary from
day to day and month to month, unlike with a UV unit. I check from
time to time, and when step #6 is darker than both five and seven,
it's ready. This may seem strange, but you'll see what I mean if
you try it. It has to do with the self-masking thing I think.
Anyway, the lower steps get darker and darker and then they begin to
reverse. When 1-5 has reversed but six hasn't, it's done. At least
that's my test. Of course, this is only for negatives that have a
perfect density of about 0.35 in the shadows to 1.9 in the
highlights. Negatives with overexposed shadows might have to be
printed until step 7 or 8 is the lowest unreversed step. Again,
you'll see what I mean if you try this.
It really is helpful to have a densitometer, but it's definitely
possible to make good cyanotypes without one.
A helpful book on getting everything calibrated without using a
densitometer--ie your shadows and highlights, and exposure and
development--is The Practical Zone System by Chris Johnson. If you
go through his simple process, your negatives will start matching
your cyanotype emulsion better. Then you can use this same testing
process when you do albumen, or any other process.
--shannon
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