Industrial high precision lost-wax usually has a mold made from many layers, often either done in traditional monlith casting frames (big slabs of cement or plaster or casting sand or etc) or formed by dipping the parts into various cement slurries (a bit like a candle. The first few layers are generally a low-additive "print coat" made from ceramics akin to porcelain (that won't react with the material being cast), and then for strength they're bulked up with thick layers of stuff that usually has been bulked up with sand and recycled shells of precious castings that have been crushed down.)

It's a fascinating process.

Just a Lemmy shitpost comment, don't think about it too hard Sure fine sand and a runny plaster, ceramic capture detail. But you still bulk it out with rougher stuff to give the mold heft.

Maybe not cement. But I also wouldn't recommend doing back yard casting for Life critical parts if you're asking what your detail capturing materials should be and what your bulking out materials should be.