Re: old cyanotype formulae

[petermarshall@cix.co.uk (Peter Marshall)]

> 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
> 
> http://www.grupponamias.com/index_en.html
> http://spazioweb.inwind.it/albertonovo/index_en.html
> 
> 
Alberto,

There is an awful lot on this in Mike Ware's book 'Cyanotype'
ISBN  1 900747 07 3

One point to remember is that the green salt was first prepared in 1897. 
Mike Ware has a 'scattergraph' of compositions of about 60 published 
recipes (Fig 2 p52) with circles for the brown and crosses for the green 
form.

Some of the different formulae are simply calculation errors by textbook 
authors, though they may still work as well. 

The one in 'The Keepers of Light' is based on an earlier recipe which at 
some stage someone forgot was made by adding 50mls of A to 50mls of B and 
gave the amount of each substance on the basis that there was 100ml of 
solution, thus halving the concentration of each solution. 

Other variations have resulted from rough conversions from imperial to 
metric units. Another pitfall has been the assumption that old formulae 
were in 'avoirdupois' when in fact they were in 'apothecaries' measures. 
Fortunately a fairly wide range of proportions will work.

Herschel did indeed invent the process as we know it in 1842 (although 
others including Smee should perhaps share some of the honour with him) 
and it was used by Anna Atkins in the first photographically (or 
rather photogramically) illustrated book the following year.

Peter Marshall
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