George wrote:

snip

Lost wax is about vents and centrifuges, isn't it? Did some back in HS.

No vents required for jewelry and small sculpture
invsestment casting - the investment is pretty
porous to air under pressure. As for centrfuges,
that sounds like a big, sophisticated machine, like
The Vomit Comet they used to get pilots and
astronauts accustomed to high Gs.

For small casting a spring wound, "break arm"
device works just fine. The "break arm" had
a pitvot point between the mold and crucible
full of molten metal (up to 6 troy ounces worth)
and the rotation center's axis. The molten metal
was kept traveling towards the mold rather
than being slung out the side of the crucible
(actually, the metal wanted to stay still and
the crucible would move out from under it

With good technique you could cast finger
prints and I once cast a dragon fly and
had the compound eyes come out in metal,