Very helpful information -- thanks for the thread! Gotta keep this short because I'm supposed to be working, but how does one know when the 'pre-fog' point has been reached? And to ask an even dumber question, what's a good way to test for fog -- visual inspection, magnifying glass, microscope?

Oh yeah, one more 'easy' question -- if adding hypo is done per mole of silver (I assume you mean silver halide), how can I tell how much silver nitrate has been converted?