Have you tried keeping solutions of the silver nitrate, tartaric acid, and
ammonium citrate in seperate bottles, and making up the volume of
sensitiser required ( using a small syringe for each solution) immediatley
prior to coating? This should eliminate the problem of the silver
precipitating out of solution over time.
It certainly works with the Kallitype sensitiser but I have never tried it
with V.D.B.
Of course, you may need to add an antiseptic to the ammonium citrate
solution ie thymol, to prevent "hairy things" growing in the bottle!
Tony McLean.