You use a master to make a silicone mould, then you use the silicone mould to make a wax positive, then you use the wax positive to make the investment (sand or whatever medium you're using), which is preheated for the metal casting, so it won't crack when the metal is poured in, and to evacuate the wax (hence "lost wax" casting), then the "sand" is broken away after the metal has cooled, and you have your rough casting. After this, you will have to clean up the metal - remove any runners, polish, bore, drill a vent/touch hole, and you've got yourself a barrel. The silicone mould is reusable a number of times, and the master is too, of course, depending on what it's made of and how it's cared for.
To answer your question, most of the moulds are destroyed, but not all, since there are a series of different moulds used in the process.
Tell me if I left anything out, won't you Gary?
