[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: old cyanotype formulae
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.
In a message dated 5/21/02 3:22:31 AM Eastern Daylight Time, firstname.lastname@example.org writes:
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:
> 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%
> PH> 2.3 Ferric Ammonium Citrate(brown) 20% 100cc
> Potassium Ferricyanide 16%
> He states:"the addition of small quantities of dichromate increases the
> contrast. Triethanolamine (1cc) increases the sensitivity and reduces the
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.