The lost wax casting process for jewelry starts with a wax.  This can be a hand carved wax, a 3D printing or one from a mold.  Here you see a wax being made by shooting hot liquid wax into a mold.

After the hot wax is shot into the mold, it solidifies very quickly and then is removed from the mold.  Here the mold has been separated and the operator is in the process of removing the wax.

Here the wax is shown completely removed next to the mold.

The next step is to attach the wax by the “stick” (or spu) that extends from the piece, which was the entry point for the liquid wax, to a large cylinder of wax .  This is achieved simply by melting the end of the spru into the center cylinder.

When finished the whole assemblage, containing numerous different pieces to be cast, is set in a base.  This assemblage is called a “tree.”

The tree is placed in a retaining vessel called  a “flask”.  Here the tree is next to the flask it will be put in.

The flask is placed in the investment-filling and vacuuming machine.

The machine is filled with a number of flasks

The machine has been closed.  The flasks are in the chamber below.  The big steel cylinder on top is where the investment is mixed and then poured into each flask through the nozzles with the red handles.  The investment arrives at the casting facility in dry, powder form.  It is mixed with water and a “binder” and then poured as syrupy liquid into the flasks.

The a flask is almost full.

Once all the flasks are full, the whole chamber in which the flasks sit is evacuated.  In this way any residual air that is in the investment is pulled out eliminated air pockets that could fill with precious metals during the casting, ruining the casting.

After evacuating, the machine is opened to remove the flasks

The flasks are moved to an oven where they will be heated according to a careful timing protocol to temperatures generally above 1000 F.  This will be run by a programmed controller and will happen automatically overnight so as to be ready to cast at the desired time the next morning.  The heat first melts and then burns the wax out.  It totally vaporizes and comes out the top of the flask leaving a negative impression of all the items in the flask.  This is why it is called “lost wax casting.”

The next morning the hot flask, heated to the desired temperature, is removed from the oven.

It is placed in the vacuum caster.  The hardened investment is porous.  Once the metal is melted it will be poured into the top of the flask.  The vacuum caster will be drawing a vacuum all around the flask thus evacuating all the negative images of the pieces that are being cast. This vacuum not only pulls out the air but will pull the gold down into the flask and all the tiny areas of detail of the pieces being cast.

Meanwhile the gold is melted in the induction melter. 

All the metal that was melted in the induction melter is poured into the flask in the vacuum caster. 

The flask is removed from the vacuum casting machine and is immersed in cold water to “quench” the metal and remove the investment.

While in the water a stream of water under high pressure is shot at the flask to help loosen the investment

After a time it is removed from the water.  Usually at this point it still has quite a bit of investment attached.

It is further subjected to the stream of high-pressure water jet.

Here is a cleaned tree after casting set back in the flask base along with a smaller one laying down next to it.  The big one is white gold and the small one yellow.

The tree is weighed to calculate casting loss.

The individual cast pieces are cut off the central trunk of the tree.

Many pieces accumulate around the cutting machine as the cutting proceeds.

The finished casting are now ready to be sent to the jeweler, setter and polisher for finishing.