I hate zinc. Made me sick everytime I melted it. But if you do, drink milk first. It helps. Since it has the same mass as iron, you may consider it worth your while. It does shrink bad, though. So make sure your ball cavity is well below where you intend to pour the zinc. Large feed hole and large risers, and fill it to the top. Aluminum is not nearly as difficult; sets up faster, and can be made hard or soft, depending on your alloy. Pop cans are nearly pure, and soft. Auto parts have a high iron content, and are much harder, stronger, and easier to machine. But temperatures much over 1300 make it harder to pour. Aluminum will shrink, and the bigger the ball, the more chance. Pour quickly and fill your mold to avoid shrink cavities. It will shrink, anyhow, so if you start with bore size, it won't be by the time you get finished. And you'll get a lot more balls to the pound.Avoid anything wet or cold coming into contact with the metal, or it will go off like a stick of dynamite!
