Resazurin not turning pink

I want to add [resazurin](https://en.wikipedia.org/wiki/Resazurin) to my media as an anaerobic indicator.


To my understanding, the resazurin is blue when first added to the media, then turns pink after autoclaving, and finally it turns colorless when adding a reducing solution (sulfide in my case). However, **I’m having trouble to make the media change from blue to pink**. I’ve autoclaved and it’s still blue. My media contains KCl, NH4Cl, KH2PO4, Na2SO4, NaHCO3. I'll add sulfide and other metals after autoclaving.


Should I flush my media before autoclaving? what controls that first reduction step? Heat alone seems not enough to reduce the resazurin. Should I add another reductant in addition to sulfide?


