This PADCO brand cotton batting can be used to seal the opening of an Erlenmeyer flask during sterilization and colonization. The dense cotton provides an excellent barrier against particulate contaminants, but allows some air/gas exchange.
We recommend using this cotton batting instead of polyfil or micropore tape for sealing flasks. You will need cotton batting if you plan to make mushroom liquid culture or agar medium in an Erlenmeyer flask.
Cut a piece of cotton batting approximately 4" wide.
Fold the piece of cotton twice (like how a towel is folded in thirds) and roll it up.
Insert snugly into the mouth of your Erlenmeyer flask.