Have you tried a very weak solution of the selenium/sulfite (I take it you
dissolved it in sodium sulfite) with about 1% EDTA (tetrasodium) added?
You're making me wish I got back into the chemical experimentation thing!
You work (as I see it) very empirically, as do I, but I don't like to put
all my formulas in one basket, as it were, and try steps to the correct
solution. I'm very interested in your work, and when I pay off for all the
computer stuff I've acquired, plan to buy some additional chemicals and do
some formulation to find out what all the problems are.
Incidently, almost any organic sulfiding agent should provide brown tones
with Kallitype or any other silver process, but sodium sulfide tends to
decolorize very fine grained silver images. That's why I'm conjecturing
that possibly a very weak selenium should work.
Did you ever get the chance to see my article in the 1950 (! - that's
correct: 1950) issue of the American Annual of Photography, titled "A Study
in Brown Toning"? It pretty much explains the theory.
Sil Horwitz, FPSA
Technical Editor, PSA Journal