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argentotype again

I've had a reply offlist from Mike Ware (he is not subscribing) about the argentotype recipe. See below.
Dear Alberto,
Your outline description of Herschel's argentotype is correct - but I cannot add much in the way of further details. In his 1842 paper to Phil. Trans. he only mentions it in the Postscript, Art. 218, on p. 210. Here is a copy of Herschel's original text:
218. If paper prepared as above recommended for the chrysotype, either with the ammonio-citrate or ammonio-tartrate of iron, and impressed, as in that process, with a latent picture, be washed with nitrate of silver instead of a solution of gold, a very sharp and beautiful picture is developed, of great intensity. Its disclosure is not instantaneous; a few moments elapse without apparent effect; the dark shades are then first touched in, and by degrees the details appear, but much more slowly than in the case of gold. In two or three minutes, however, the maximum of distinctness will not fail to be attained. The picture may be fixed by the hyposulphite of soda, which alone, I believe, can be fully depended on for fixing argentine photographs.
He does not specify the strength of the Fe am cit solution in this paper, as you will see from the quotes in my "Gold in Photography" pp 68-74, but I have discovered elsewhere that he used 1 part of Fe am cit to 9 parts of water, typically. I do not know the strength of his silver nitrate solution.
I have seen some of Herschel's argentotypes, at Oxford, Bradford, and at HRHRC Texas, and they are faded, compared with his original description. I think he made very few of these iron-based silver prints.
Best wishes,

On 16 May 2009, at 11:45, Alberto Novo wrote:
All I know about argentotype is that it was a (presumabily) Fe am citrate coating developed in silver nitrate. I have a Namias' formula for a brown-black callitype developed in alkaline silver nitrate which might be a more refined approach, but I would prefer to cite the original formulation.