old cyanotype formulae

["alnovo@inwind.it" <alnovo@inwind.it>]

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

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