Which bleach did you try? I meant the photographic bleach like potassium ferrocyanide that Doremus Scudder mentioned.
I was angry enough with that stain that I tried both.
First I tried a Berg Blue toner which I think bleaches and dyes the print normally, but it had no effect. Then I tried Chlorox. Still no effect.
I only have chlorox on hand. But I'm getting very inconsistent results. My first test with the toner (the one I first posted about), I ended up leaving it in straight undiluted selenium for several hours just to see what would change (nothing, as far as I can see). But!, this is the only test piece that the chlorox did not destroy, similar to yours.
Did several more tests with dilutions ranging from 1+5 to 1+20 for between 1 and 6 minutes. Chlorox bleached all of them. Only a single test print (from the exact same paper as the rest) showed a slight purplish cast after six minutes in one of the stronger dilutions (and it still bleached) (if this one turned purple why didn't the others? why didn't the one in straight selenium??).
I'm not sure what my answer is. Should a print toned with selenium survive chlorox (or can I assume my 1+20 6min prints are good even though chlorox bleaches them?)? Should I leave them all in straight selenium for several hours (to protect from chlorox) and hope one of them doesn't turn purple?
In my experience multigrade classic should show a substantial and very noticeable colour change in selenium at those dilutions.
Interesting! I wonder what I am doing wrong?