Adam Kimball (akimball@finebrand.com)
Mon, 28 Jun 1999 16:54:10 -0700
Maylee,
Check out:
http://www.mikeware.demon.co.uk/cyano.html
This process was developed by Mike Ware and this is his paper. The page
above lists .5ml of 25% AD. So, you used quite a bit more, yes.
Are you absolutely sure that Photographer's Formulary said 20ml of 25%?
If yes, I'd absolutely demand my money back. That is way too much
dichromate.
I've been working with the process for a few weeks now and have found it
to be an absolute gem. Contrast is controllable via additional amounts
of dichromate (i.e. a drop of .5% AD to 1ml sensitizer) and use of
different clearing bath concentrations. However, I've found that a
single drop of 1.5% AD to 1ml of sensitizer to be about the limit for
acceptable prints. After this, most papers (though not all!) tend to
grain up and lose too much highlight seperation. When I have a little
more experience with this process (and when I get Mike's forthcoming
book on the subject (any week now!)), I'll post more of my experience
with it.
As for problems "clearing" the print, I really don't think the
dichromate is an issue - though I am by no means an authority on this
subject. How are you clearing yours prints? Just water? Citric,
Nitric, Hydrochloric acid? Aqua Regia? Heh. But most importantly,
what papers are you using? I've found that Arches Platine works
extremely well w/o Tween or anything else. It clears very well, and
stains almost not at all. Crane's Kid finish works wonderfully too.
However, I've never tested clearing prints that didn't have an acid
clearing phase - the contrast is way to loooong w/o the acid - I have
one wedge on Cranes Kid that shows 21 steps and could probably handle
two or three more!
So..
Firstly, get or make a new sensitizer. With 10x too much dichromate,
you'll have a very short scale and a grainy result. Secondly, get some
Arches Platine to practice with. Thirdly, clear in 4% Citric Acid. And
lastly, buy Ware's book when it comes out...
Hope that helps,
Adam
Maylee Noah wrote:
> Last summer I bought several kits form Photographer's Formulary. The
> instructions in the "New" Cyanotype kit say to use 5ml of a 25%
> ammonium dichromate solution. Photo Techniques (Jan 97) published a
> recipe similar to the kit but it calls for 1/10th as much dichromate.
> Has someone made a mistake or does the amount of dichromate not
> matter? And, since I misread the instructions, I put the whole 20ml of
> 25% dichromate solution I'd mixed up into the cyanotype sensitizer. So
> my sensitizer has 4 to 40 times more dichromate than it should. It
> works but seems to leave a light yellow stain. I can get rid of the
> stain with a sodium bisulfite solution I mixed up to clear gum
> bichromate prints (also from one of the kits). It changes the color
> some. Does it do any harm? I emailed these questions to Photographer's
> Formulary about a month ago and have gotten no response. Any help will
> be appreciated. Maylee
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