31 Sackville St <1>. London
Oct. 5/39
Dear Sir
I enclose a sheet of paper sensitive to heat, as that of a good fire, or of an iron for ironing linen<2> – I have no doubt it may be made more sensitive if wanted – Alkalies whiten it and render it insensible – acids restore the sensibility; perhaps therefore it will be well to wash this specimen with a little weak acid – The impression of heat on it, is very evanescent & may be repeated any number of times without injury or diminution of effect –
Yours truly
H. F. Talbot
Notes:
1. 31 Sackville Street, London residence of the Feildings, often used as a London base by WHFT.
2. WHFT's enclosure has not been located and is unlikely to have survived. He had experimented with the effects of heat on silver before the public announcement of photography and published 'On a new Property of the Iodide of Silver,' Philosophical Magazine, v. 12 no. 74, March 1838, pp. 258-259. He had just taken up this research enquiry again at the time of this letter. See Larry J Schaaf, Records of the Dawn of Photography: Talbot's Notebooks P & Q (Cambridge: Cambridge University Press, 1996), P115 and P139..