john... as strange as this might sound, I have had an opened bottle of Clean Shot (when it was called clean shot... that's how old it is) around the house for years. I shot some this year just to see if it was still good, and it functioned perfect. After I opened the bottle since I had no horn for the stuff, I poured it into an big empty (cleaned and dried of course) plastic ketchup bottle with a flip top spout. It has been in there ever since, and stored on the shelf in the gun room. So what I am getting at is I have not experienced the moisture problem that others have advised me of. I still would not purchase any more of it only because I like using real black powder much more then any other propellant....