44 Queen Ann St <1>
Feb. 19. 1839
Dear Sir
I have made trial of the Ferrocyanate of Potash <2> perhaps what I have obtained from the Chemists is not exactly of the same quality with yours; the following are the results I obtained this morning, how do they agree with yours?
1. simply dipping the design into this liquid, does not preserve it.
2. dipping, & then washing out with much water, only partially preserves, the design acquires an iron grey colour in sunshine.
3. if left in the liquid 2 hours, it is then preserved, but the ground changes from black to a rich yellowish brown–
I presume I have not yet used the proper method with this liquid.
I will now inform you of the 2 methods of fixing which I discovered & which I have very often employed with success; requesting you not to mention them just at present.
The first, is hydriodate of potash. This requires some nicety of management, because if too strong, it injures the ground; if properly managed it answers beautifully. The piece of lace I showed you at Slough <3> was preserved by this means, & has lasted five years – often exposed to the Sun –
But my usual plan, is to immerse the design into a strong solution of common salt. and not to wash it out. Exposed to sunshine this often acquires a light lilac tint; but if it is an object to secure perfect whiteness this may be attained by proper management.
Believe me Dear Sir Yours very truly
H.F. Talbot
Notes:
1. 44 Queen Ann Street: London home of the Mundy family and a frequent base for WHFT.
2. That is, potassium ferrocyanide. True cyanates do not feature in photographic chemistry, being uncommon and rather unstable. In this case, references to ‘cyanates’ or ‘ferrocyanates’ should be read as meaning ‘cyanides’ or ‘ferrocyanides’. Thiocyanates, also earlier called sulphocyanides, did have some photographic uses.
3. One of WHFT’s most successful early images was formed by direct contact of a piece of lace with his photogenic paper. Numerous lace images still exist in various collections.