Lost Wax
From Concrete To Bronze

Make a mold
This step is by far the most critical. All the detail which
appears on the original piece must be captured in this mold. The
mold, depending on the size of the piece, can be cut into sections
for casting.

Make wax casting
Molten wax is poured into the mold to form layers of wax. This wax model is an exact duplicate of the original casting.

Chasing the wax
The wax is pulled from the mold and hand chased (re-detailed).

Spruing
Wax rods (gates) and a pouring cup are attached to the wax casting
in just the right positions to assure a full pour.

Cast a ceramic mold
In a temperature controlled climate of 72°F (22.2°C), the wax casting is dipped into investment liquid several times. On the first dip a fine powder is applied. On the next dip a course ceramic sand will be
applied. This step is repeated several times, each increasing the
coarseness of the material to create the ceramic mold. Between each dip, the ceramic layer must cure (dry) before another
layer can be applied.

Burn-out
The ceramic shell is placed in a kiln and fired. The shell bakes and the wax is melted (lost) from the shell. This creates a hollow ceramic shell mold — hence the term “lost wax”.

Casting
The ceramic shell (mold) is removed from the kiln and immediately
the molten bronze is poured into the shell. At the time of pouring,
the bronze is 2100°F (1150°C).

Break-out
After the casting has cooled several hours, the shell is carefully broken away leaving the unfinished bronze.

Sandblasting
Any fragments of the ceramic shell are removed by sandblasting.

Merritt Herald July 8, 2003