Take a look at the ingredients in a selenium toner, and you'll be able to spot what the main source of sulfur is (and the pH that makes it stink). That Selenium toners made materials more 'archival' was essentially purely coincidental. A tiny residue of Sulfur is the key here - which basically means use hypo-clear (not hypo-eliminator) and a reasonable wash, but don't overwash. The point of Se toning should be for colour/ density change (by which point you've more than sufficiently sulfurised it) rather than for any claims of archivalness - it just happened to be the one reasonably common toner that could be diluted enough to not affect image colour significantly (and which has other archival test uses for adequate fixing).
So in my reading about selenium toning, I'm seeing things about how so-called "light" toning, traditionally done to improve image permanence, is not worth doing. But I'm unable to actually find any data or primary sources...
Take a look at the ingredients in a selenium toner, and you'll be able to spot what the main source of sulfur is (and the pH that makes it stink). That Selenium toners made materials more 'archival' was essentially purely coincidental. A tiny residue of Sulfur is the key here - which basically means use hypo-clear (not hypo-eliminator) and a reasonable wash, but don't overwash. The point of Se toning should be for colour/ density change (by which point you've more than sufficiently sulfurised it) rather than for any claims of archivalness - it just happened to be the one reasonably common toner that could be diluted enough to not affect image colour significantly (and which has other archival test uses for adequate fixing).
I was merely pointing out what that article expresses in more words - a certain level of sulfur will enhance archivalness, but unless you selenium tone so far that you get what (to many) would be an objectionable colour change from conversion to selenite, whatever enhancements in archivalness you might attain are from sulfur compounds that you either intentionally add or fail to wash out. In other words, it's mostly about the wash step(s) rather than toning.