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Re: Formidine sulphinic acid toner?
I have written a couple of articles for the U.K. photographic magazines,'
Darkroom User' and 'Photon' on the subject of F.S.A. a.k.a. thiourea
dioxide. I've just searched my hard drive and it appears as though I have
now deleted those files.
Strictly speaking, F.S.A. (formadine sulphinic acid) is not a toner in the
conventional sense. It is an efficient reducing agent that reduces the
re-halogenised silver back to its elemental state. You can use any one of a
number of bleaches that converts your image to the bromide, chloride or
even iodide and re-develop the image in a solution of f.s.a. that has been
made alkaline with sodium carbonate or hydroxide. The pH of the f.s.a.
solution and the choice of bleach and paper are the factors which govern
the colours/tones of the final image, which can range from blue/black
through red brown to even yellow/green. Unlike most indirect toners, there
is no loss of image density during this process. In fact, the image is
If you are interested, e mail me off list and I will send you a scan of
'Darkroom User' (now called Camera & Darkroom) with the relevant
information which will get you started.
Perhaps it may also be of interest to Judy for P.F.?
Cheers ........ Tony McLean