I posted an item earlier on the experience I had of trying out Herschel's
experiment in class of exposing paper coated with ferric ammonium citrate and
developing it in gold chloride ( hydrogen terachloroaurate ). The result was
beautiful, deep blue blacks and blue greys. But I have not been able to make
another as good. I have made others but you use a lot of expensive solution this
way
I have also tried substituting 1% gold chloride for the platinum in the classic
platinum recipe; it works but you need a negative of a limited range of tone.
Adding one drop of palladium chloride 20% solution to the sensitiser produces an
image with pinkish high lights, that some like. I included one of the prints in
the recent Melbourne and London alt photo shows. It was listed in the catalogue
as a 'pterigold' print :-).
I am about to try John Rudiak's variation which should give greater stability to
the reaction and a more powerful image as it uses about a 20 % gold solution.
Terry King