Located a couple carboys under my basement stairs that I had forgotten about for a while. They had been filled to the rim with hot water and PBW and left to sit until I needed them again. I finally had the time to give then a proper cleaning and while the inside of the carboys are sparkling, the PBW has left a ring "around the neck" that even a carboy brush can't remove. The ring is barely noticeable, but I know its there and it bugs me.
Do you guys think these would be safe to brew with or should I keep trying to get rid of that "stain"? At least I know its from a cleanser and not from fermentation filth. Any thoughts?