Bronze Casting - Step 10
The Wax Model - Step 1

Bronze weighs about 509 pounds per cubic foot. So for both practical reasons of moving the sculpture around and to keep the cost within reason, solid sculptures are usually avoided. Unless they are small, wax sculpture are usually cast hollow.

But to have a hollow bronze cast from the lost wax method you need a hollow wax model. As we said, here we will use the "slush" technique. You melt the wax (details avoided lest the misguided try it without proper instruction and facilities) and pour it into the mold. You "slush" it around coating the inside of the mold and then pour it back into the vessel. After the layer solidifes, you again pour in the wax - it still should be liquid - in again and repeat the slushing. Again you let the coating soldify.

You repeat the pouring, slushing, and pouring the wax out of the mold until you build up a layer 3/16 of an inch. Let it cool and you should have a nice wax cast in the mold - although thin spots (identified by holding the model to a light) may need to be patched up.