Re: old cyanotype formulae

[CCBaggett@aol.com]

Alberto,
       Sorry, you are correct. It is ferricyanide not ferrocyanide. that was a typo on my part. By the way I agree with those who recommended Mike Ware's Cyanotype book. I can't find my copy or I would ahve quoted him. I also agree with Judy Siegel that a lot of this old information is riddled with errors. 
Cheers,
Charlie


In a message dated 5/21/02 3:22:31 AM Eastern Daylight Time, alnovo@inwind.it writes:


> Wonderful, Charlie.
>
> I need only a little explanation:
>
> > Photography Theory and Practice by Clerc dated 1930 gives two formulae- one
> > for green citrate and one for brown:
> > Green:
> >        Potassium Ferrocyanide
>
> Is this correct? I have found only one formula using ferrocyanide (saturated, with 50% brown fe. am. citr.), but I believed this was a mistake.
>
> > Photographic Chemistry Vol. One Pierre Glafkides English edition dated 1958
> > from the French edition dated 1957
> >
> > Ferric Ammonium Citrate formulas:
> > PH < 2.3            Ferric Ammonium Citrate(green) 25%                  100cc
> >                          Potassium Ferricyanide 12%
> >    100cc
> >
> > PH> 2.3             Ferric Ammonium Citrate(brown) 20%                 100cc
> >                          Potassium Ferricyanide 16%
> >    100cc
> >                          Ammonia
> >               1-4cc
> > He states:"the addition of small quantities of dichromate increases the
> > contrast. Triethanolamine (1cc) increases the sensitivity and reduces the
> > contrast."
>
>
> It is interesting to note that in http://jchemed.chem.wisc.edu/Journal/Issues/2001/Mar/abs311_2.html is reported an experimental study on the iron/ferricianyde photochemistry, stating that the maximun quantum jeld is in the 2-5 pH range, and that the NH4 ion is essential for the whole reaction.
>
>
>
> Alberto