I aged a RIS for about a year in a 5 gal glass carboy and there is really stubborn film where the yeast cake was sitting. I've tried oxyclean soak in hot arse water and also using a descaler acid and it's still there so I'm thinking I need to get something down in there to physically remove it from the carboy otherwise I don't know how comfortable I feel using it again until I can remove this film, don't want to ruin a batch due to this.