ceramic shell is made up of as many as twelve layers of investment
(the greenish-yellow liquid slurry). After the layers dry, the shell
is heated up in a large
kiln to harden and, at the same time, melt out the wax. On the day
of the pour, it is reheated to 1600 degrees before the molten
poured into it. The thin shell withstands quite a beating, but can still
produce details as delicate as a thumbprint.