From: Darlington Media Group (postmaster@mediaworkshop.demon.co.uk)
Date: 11/25/00-03:13:46 PM Z
Hi.
Any alkali will 'bleach' cyanotypes ie. reduce the Prussian blue to
Prussian white ... so borax, sodium carbonate, potassium hydroxide et al
will work. Personally. I would stay clear of chlorine bleaching agents
which could damage the cellulose structure of the paper base.
If you wish to make an 'alkaline resistant' cyanotype you could immerse the
print for thirty minutes or so in a nickel (II) salt such as nickel
sulphate or nickel nitrate. Note: nickel salts are toxic and can lead to
sensitisation of the skin. Just treat it with the same respect as you would
a selenium toner.
The nickel salt will produce a colour shift towards turquoise which is not
at all unpleasant. If you are feeling really wild, then you could even
produce a red cyanotype by immersing the nickel toned print in a 1%
solution of dimethylglyoxime, (This is a elementary chemical test for nicke
salts.) and this can be subsequently removed with any acidic solution.
Before anyone congratulates me on my encyclopediac knowledge of chemistry,
I must confess that the above information is contained within the pages of
Mike Ware's excellent book on the 'Cyanotype". You've just got to know
where to look for it! ;-)
Why not take a look at the latest issue of Camera & Darkroom magazine?
http://www.camera-and-darkroom.co.uk
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