I don't know if someone else has already done this but I just tried it over last night, and it worked perfectly. I tore a piece of paper towel into a square that was just a little larger than my ball jar lid, then layed it over the inside of the lid and soaked it in water. After letting the excess drain off, the paper stayed stuck flat to the lid, and I resealed the jar, trapping the wet towel in the jar, but completely out of contact with the tobacco. Just sitting over night was enough to do the trick for this batch. the towel was bone-dry and I removed it so that it wouldn't provide a path for the moisture to leak out again.