I found my best Sistan information from Ctien's "Post Exposure". If I read him correctly his position is that it is not proven and doesn't take the place of Selenium toning but it probably works as a second barrier or back up to washing & toning and doesn't hurt anything. Again no definitive studies mentioned.
Originally Posted by Ed Sukach
I am convinced enough to try it and finally found a bottle to start using but haven't yet. I don't know if it is a one-shot type chemical or if it can be stored for any period of time and reused? Ctein says he does not reuse it more than one session but doesn't say why.