Ok on aluminum casting (im no expert by any means btw) An investment casting is a casting in where a wax pattern with sprues attached, like a ring or in this case her is "invested" in plaster of paris, the investment is then placed in a kiln, or something hot, to melt/ burn out the wax and dry it completely. metal is then poured into the sprue, and the plaster is chipped away when it is cooled. however i cheat on my simple plaster of paris castings by just pouring the plaster over a plastic matrix and just letting it dry afterward- since there is nothing on the back of "lady" i can just use that as an open mould. then i just dry that in a dehydrator, then pour. but for 3d things you need to do wax. I also plan to put "lady" on ebay just to see how my castings do, as i need cash to buy blacksmithing stuff. As for the difficulty of aluminum casting id say its pretty easy, it takes less skill, but alot more time overall with blacksmithing. I started out melting in a flowerpot, cast in concrete in an ash bucket, with charcoal. i also do most of my castings in greensand, just my detailed things like "lady" in plaster.- id say if your interested give it a try. check out melt metal, home metalcasting, backyard metalcasting
Also i hope to build a forge to better suit my needs soon, out of furnace cement- i want to put a notch in either side, so i can heat metal on more places than just the end and i want it to hold up. am i going wrong with refractory, as i am a foundry guy and concerned about insulation, will something out of heavy steel work too?