Welcome to the world of casting. Your cost of shooting will go down so you can shoot more !! In my opinion, best to get the initial melt as clean as possible so there is less contamination in our casting pot. I have been know to melt it more than once to get the alloy clean. When melting wheel weights, you want to keep the heat low enough so zink will not melt, so you have time to get it out before contaminating your alloy.