I think that from your descriptions, the prints were underfixed. The reason I think this is because when you fix prints, you're removing the unexposed and undeveloped silver halide salts from the paper. When you bleach the prints with toning bleach, the metallic silver that forms the image, is converted into silver halides and any undeveloped silver halide salts remaining in the paper will also rehalogenise. When you put the print into the toner, the toner converts the halide salts into silver sulphide, which forms the toned visible image. So any silver halide salts that didn't get removed by the fixer will become visible as a yellow or sepia stain. hence the stain when you did your test.
Perhaps your fixer was exhausted, not strong enough, or you didn't fix long enough. I don't know. I've never used alkaline fixers so I don't know how effective they are. You could change to a standard acid fixer like HYPAM if your problems persist.
If it was a washing problem, any fixing salts (thiosuphates) remaining after fixing will combine with the toning bleach (potassium ferricyanide) to form Farmer's Reducer which can erode the rehalogenised silver salts. You'll notice the disappearance of fine detail and light, subtle tones. These is ammonium thiosulphate in selenium toner, so always wash well after selenium toning prints, especially if using a fibre-based paper.
You might find the following web page useful: http://unblinkingeye.com/Articles/Ar.../archival.html Good luck, I hope you solve your problems. :-)
Last edited by kevs; 12-11-2012 at 02:59 PM. Click to view previous post history.