Thank you to everyone who has responded! Special thanks to Doremus for his detailed and very useful post.

I have actually used selenium toning as a casual indicator of the quality of paper processing. If the paper stained or had mottled areas in the toner it was a rough indication of something wrong in the earlier processing steps. However, this isn't something I'd want to always rely on--I'd rather be certain of the quality of my processing rather than guessing.

************************************************** ****************************

So another question--I've ordered one of the residual silver test kits from Photographer's Formulary. It uses sodium sulfide as the test agent. To anyone who has used it or something similar before, how reliable is this test?

My intention is to take my plain sodium thiosulfate fix solution and fix strips of paper for 30 seconds, 1 minute, two minutes, five minutes and ten minutes in the homemade fix. Then test each strip with the kit and see at what point the paper was fully fixed; then add just a bit more time to the indicated fully fixed strip as a safety margin. (That's the advice for film anyways.) Sound reasonable?