Stupid question, but why is cotton annoying you?
It doesn't wick as perfectly as I'd like it to.. and gets dark and nasty looking after just a couple days. Part of the reason for that is I've been using really crappy 100% VG local juice, (got better stuff on the way). Regardless, while cotton still might work "fine", if Rayon's better for the purposes of wicking, why not use it instead?