Gilbert van Reenen (clean.green.images@clear.net.nz)
Tue, 09 Mar 1999 09:02:55 +1300
I have had success toning cyanotype with Gallic acid which also comes in
powdered form and is of low solubility.
The formulas I saw in a reference appeared to be extremely empirical so
treated them accordingly
the cyanotype needs to be soaked in a weak alkali first sodium carbonate or
ammonia solution then rinsed then soaked in approx 1% solution of the gallic
acid.
The results vary considerably with the initial exposure state of the print
and the type of paper on which it is printed.
On good strong cotton paper the effect is a very warm dark brown
Cellulose based papers tend to stain more
A number of other organic acids are likely to be useful for this process.
I am about to experiment with caproic acid
Gilbert van Reenen
Clean Green Images
Ballantyne Road, RD 2
WANAKA New Zealand
phone (64) 3 443 7951
fax (64) 3 443 7889
http://www.cleangreen.co.nz
-
. I do use tannic acid but the powdered
>version and mix it 30g to 1,000ml of distilled water. For purple black I
>bleach the print with 125ml of ammonia to 1,000ml of distilled water for
>less than a minute, wash the print and then tone it in the tannic acid for
>5 minutes. Be carefull with the ammonia, where a mask. Its the only toning
>I know that is stable. If anyone knows of other stable toning methods for
>cyanotype I would love to know.
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