As for leaving powder in the hopper, I just don't. Never did. Not out of a concern for turning the hopper yellow, which it has after 45 years of use anyhow, I don't because I feel the sealed container is best for it. My original reloading station was an un-A/C'd storage room in the carport of base housing. Then it was basements of base housing followed by the basement of my house in WA--none with A/C-- and now the kitchen counter--but at least it's in the A/C. I may have left powder in my dropper once overnight, but otherwise, back into the jug it goes.