This is a little tip from me to you. When you buy new supplies that have a lid, put a little bit of Petroleum Jelly on your finger. Run it around the rim of the new lid and then screw the lid around a few times. Your paints, gel mediums, and even gesso won't stick in the grooves and you will be able to unscrew that lid the next time you want to use it!
I guess you could call this a...Lube & Screw Tip.