First of all you make the model, it can be made of any rigid material (that it's not sticky), I'm using wood and plastic for this. When you have the model exactly the way you want the copper block to be you make the mold, there are 3 materials you can use, I don't know their names in english but they work similary to each other: they are all a kind of very thin sand, once of them gets rigid with heat (this one can only be used with metal models otherwise when you heat it the wood model would burn), there's another one wich gets rigid when you inject CO2 into it and the third and most popular/traditional is what they call "green sand" it has a certain degree of humidity and some chemicals in it so if you compact it a lot (using a little wood hammer os something like that) it gets solid and won't fall apart unless you hit it.
After making these molds (lots of them) and making sure they have no failures you put the copper in the blast furnace, inside a special "bucket" made of compressed graphite, copper's melting point is 1085ºC, so when it gets a little hotter than this (so it won't solidify again too quickly) you get the quantity you will use for one mold with a tool that resembles one of those things (silverware) you use to serve punch, of course it's made of iron and has a very big cable so you won't get burned, you throw the liquified copper inside the model and there you go, after that it's just some finishing job like lapping, drilling holes for screws, assembling the top of the block wich is made separately and stuff like that.
About the O2 in the copper I buy only quality copper and no oxygen gets in in the cast process (as far as I know). Anyway the difference between the thermal properties of "common copper" and that copper treated to remove as much oxygen as possible are minimal.
Bruno Facca
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