[Alt-photo] Cuprotype, Cyanotype-Toning Trials

udo.schnitzbauer at uzh.ch udo.schnitzbauer at uzh.ch
Thu Sep 27 06:44:55 UTC 2018

Dear List, 

here are a few results of home experimenting:

First I tried the Cuprotype Process by Jim Patterson:

Yesterday I played a little bit with cyanotypes and the formula:

Tried to tone a exposed cyanotype (Exp. 11 and 5 min) with a bath made out of copper(II)sulfate and ammonium citrate. Reason for that, was this patent https://patents.google.com/patent/US2093421A/en
where I read this: [...]Upon exposure a piece of blueprint paper (a) becomes more and more blue and then (b) fades out to a light blue grey (c) becoming greyish White when Over-exposed.  During (a) the ferricyanide is being reduced to ferrocyanide for a piece of paper at this stage when washed in an ammonium citrate-copper sulfate solution (from which ferricyanide will not precipitate copper ferricyanide but ferrocyanide will precipitate red copper ferrocyanide) gives a red print. [...]
I got (at picture not visible) light reddish tones and the blues turned to more blackish color, perhaps I had to adjust the concentration of the copper(II)sulfate higher....

The other trial was playing with the formula itself:
In short: To 5 ml potassium ferricyanide and 5 ml ammonium iron(III)citrate solution I put 10 ml of a "copper solution" (composition see the posting). Despite of the precipitation of copper(II)ferricyanide the solution would be applied to paper (difficulties to get a smooth and striation free surface with the brush; if a glass rod works better??), dried (cold air with a fan) and exposed for 6 min with UV and after that the print washed with running water, the print shows a reddish tint which blacks which are different from the cuprotype before. 

If I find a way either to get a nice spreading of the "emulsion" or to avoid the precipitation of copper(II)ferricyanide (alternativ make it colloidal, so that this stuff is not disturbing anymore) it would be a nice cyanotype-mix for reddish prints.


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