To check the custard for doneness, swipe a finger across the back of a metal spoon. When the custard is done, the line made by your finger will remain without the custard running back together.
To ripen ice cream in a traditional-style ice cream freezer, after churning, remove the lid and dasher and cover the top of freezer can with waxed paper or foil. Plug the hole in the lid with a small piece of cloth; replace the lid. Pack the outer freezer bucket with enough ice and rock salt to cover the top of the freezer can, using 4 cups ice to 1 cup salt. When using an ice-cream freezer with an insulated can, after churning, remove dasher; replace lid. Cover the lid with ice and cover with a towel.