Lee's aluminum molds need a good preheat as they lose heat rapidly unless you are using a 6 cavity or high weight mold that takes a lot of lead per cycle. With a ball mold, it takes hot lead and a lot of cycles to get it to temp. Dip the corner of your mold into the lead to get it to casting temp then, cast quickly to keep it up to temp and preventing wrinkles. If you start getting a frost looking finish, slow down on the casting tempo until you get the proper pace sorted out. If you are casting pretty fast and still getting wrinkles, crank up the lead pot temp another 50-100F. And remember all this can vary some with the ambient temperature you are casting in.