TALBOT3950

31 Sackville S^{t 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 linen² – 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