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Re: old cyanotype formulae
Alberto,
Photography Theory and Practice by Clerc dated 1930 gives two formulae- one for green citrate and one for brown:
Green:
Potassium Ferrocyanide 80grams
Ferric Ammonium Citrate 180grams
Water, to make 1,0000cc
Brown:
Potassium Ferricyanide 50grams
Ferric Ammonium Citrate 95grams
Water, to make 1,000cc
With respect to green and brown, he says: "Of the two papers prepared in this way, that with the green citrate is more suitable for use with vigorous negatives than that prepared with Brown." Footnote: The ratios of opacities of a negative yielding a just perceptible blue deposit and that producing a blue of maximum depth( measured after the prints have been washed) are 47:1 and 34:1 respectively for green and brown citrate. the addition of a small amount of bichromate to the sensitizing mixture allows of soft negatives being printed.
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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." He also gives a formula for Ferric Potassium Oxalate which he says is faster than Ferricitrate, but the paper dows not keep as well. Let me know if you want that.
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Photographic Facts and Formulas E.J. Wall dated 1924
A. Ferric Ammonium Citrate(red) 250grams
Water 1,000ccm
Filter
B. Potassium Ferricyanide 200grams
Water 1,000ccm
Filter.
He states: "The ferricyanide must be in perfectly clear ruby-red crystals clear from any adherent yellow powder;...."
A. Ferric Ammonium Citrate(green) 125grams
Water 1,000ccm
Filter, and add:
B. Potassium Ferricyanide 45grams
Water 1,000ccm
Filter. Further, "Brighter prints are obtained by the addition of 0.5% of Oxalic Acid to the above; the paper keeps better if 0.05% of Potassium Bichromate is added."
Hope these are helpful.
Cheers,
Charlie Baggett
In a message dated 5/20/02 9:51:56 AM Eastern Daylight Time, alnovo@inwind.it writes:
I am writing some notes on cyanotype formulae, and a brief reasearch in Internet gave me about 20 differen recipes.
Among these, the so-called "classical" (see P-F #5, p.34) with 20% Fe Am. Citrate + 8% Pot. Ferricyanide, but also 10% + 5% (http://photography.about.com/library/weekly/aa061801e.htm), 25% + 16% (http://www.dmuenzberg.de/cykassl.htm), 24% + 7% (Rodolfo Namias, Photographic Chemistry Vol. II, pag. 204 - VII Ed. - Milano 1929 -in Italian) and so on. Moreover, the ratio Fe citrate / Pot. Ferric. spans from 0.7 (http://www2.truman.edu/~jobrien/JINS/Cyanotypes.pdf) up to 6.25 (http://personal.riverusers.com/~jdf/todd_walker/blueprint.html), while the "Classical" ratio is 2.5.
Perhaps some formulations have been set up by an author for his chemicals, paper, quality of water, and for his personal taste about the blue, but I am wondering who were the true ancestors of these formulae. For example, Namias 1908 and 1927 has the same I have reported.
Anyone has some other indication (Clerc, Glafkides, or even older) ?
Alberto