Re: Cyanotypes

Alan Kleiman (akleiman@infoabc.com)
Sun, 19 May 1996 17:43:48 -0500

>Some time ago, Alan Kleinman asked: < Does somenone know the reaction that
>ocures in the cianotype proces?>
>Kosar (Light Sensitive Systems, 1989, p. 28-37) explains:
>
>1. During exposure, the ferric ammonium (III) citrate is reduced to the ferrous
>salt:
> Fe2(C2O4)3 -> uv -> 2Fe(C2O4)+2CO2
>2. During development together with potassiumhexacyanoferrate(III) Turnbull's
>blue is formed:
> 3Fe(C2O4)+K3[Fe(CN)6] -> Fe3[Fe(CN)6]2 + 3K2C2O4
>3. Also during development, the potassiumhexacyanoferrate(III) is reduced to
>potassiumhexacyanoferrate(II), thus forming prussian blue:
> K4[Fe(CN)6]+2Fe(C2O4) -> Fe2[Fe(CN)6]+2K2C2O4
> 3Fe2[Fe(CN)6] ->o-> Fe4[Fe(CN)6]3
>
>Klaus Pollmeier
>
>Thanks Klaus
Alan Kleiman
akleiman@infoabc.com