I have another one for you...water molds. There was a process called freezecasting where you made molds for your cores using ice. These were then coated with a gel slurry and left to set up. When you baked the cores to set them, the water melted and you had hollow core molds. In fact you could do the whole casting with one lost pattern if you were clever enough to figure out how to assemble your multi-piece mold and cast the ice so when you put it together for slurry coating they would be trapped in position. Whew...talk about a run on sentence. I think I'll try to track it down, so you can view what I described.