Dental floss seems to always come in some kind of plastic, be it a plastic bag or hard plastic case. I thought it’d be easy to just find a naked roll of the stuff, but not so much.
And I added my own comment to her comments section: Thank you for this thorough writeup. It seems like it should be a simple thing to just offer a floss that’s wound on a cardboard spool, and does not come in a plastic bag or box, and does not come with metal cutting attachment (let people cut it with their own knife or scissors). What I finally tried that worked is Nymo thread, a very fine thread used for beading. It comes on a plain cardboard spool, and I already have many rolls of it in my beading supply kit. I used it plain; and also tried waxing it with beeswax. Works well either way.
BTW, My Plastic Free Life looks like quite an impressive blog. Apparently its author, Beth Terry, has been posting since 2007!
Ms. Terry’s book, shown on the blog, is one I’ve heard of but have not yet read. Looks very worthwhile. (Title is Plastic Free: How I Kicked the Plastic Habit and How You Can Too.)