Alfred Swaine Taylor to Faraday   17 April 1839¹

3 Cambridge Place Regent's Park | April 17, 1839

Dear Sir

I beg your acceptance of the accompanying Photogenic drawings, which I forward according to my promise. You can do as you please about showing them at the Conversazione on Friday evening², (at which I am sorry I cannot be present), but I should imagine that they would appear very inferior, after the exhibition of those of Sir J Herschel and Mr Talbot. All the drawings are perfectly preserved with the Hyposulphite of soda, so as to bear day light, and even sun light with impunity. Some have a red-brown others a black ground - the difference simply is, that the paper with the black ground, has been covered twice with the salt of silver, that with the red brown ground only once. The Hyposulphite of soda is used of the same strength (a satd soln) in the two cases. Caet par.,³ the longer the exposure to the sun, the darker will be the ground, on painting them with Hyposulphite. The description of the drawings are written on the backs.

As I told you on Saturday⁴, I make no secret of my process, and as perhaps you may wish to know the nature of it, I will give you a short description. One drachm of fused Nitrate silver is dissolved in once once and a half of water (1/12). Strong Ammonia is added to precipitate the oxide of silver, which is again exactly taken up by adding the Ammonia drop by drop. This forms a solution which is then to be mixed with its bulk of distilled water, making about <oz>iij, and here the silver salt forms 1/24 instead of 1/8 as Mr Talbot recommends. This is amply strong, and of course three times the quantity of paper may be made with it. <dr>i of Nitrate Silver will thus cover 30 sheets of paper, - <oz>i of the solution covering 10 sheets. This presents a remarkable instance of the division of matter, for in a finished drawing every square inch of paper, has not more than .009gr or 1/111 gr of metallic silver spread over it.

The drawing when made is immediately painted over with a saturated solution of Hyposulphite of soda (I used this three weeks before I saw Sir J Herschel's paper recommending Hyposulphite of Ammonia⁵, - but I have derived many valuable hints from Sir J Hs account) which removes the remaining salt of silver from the white parts of the drawing, and turns the ground red brown or black, according to what I have said in a former part of the letter.

The paper should be the superfine Bath post, - that with a blue tint I have not found to answer - believe me

My dear Sir | Yours very truly | Alfred S. Taylor

M. Faraday Esq

P.S. The outline drawings are not taken from engravings, but from copies of engravings in lamp-black on tracing paper.

Address: M. Faraday Esq | Royal Institution