Technique

Lost wax casting

Lost wax casting is used to mould various types of metal into intricate pieces of jewelry.

 

The wax casting process starts with sketching out a preliminary drawing of the piece you have in mind. Then,  a representation of the desired piece is crafted out of wax, creating a pattern with the same intricate detail that will appear on the silver piece of jewelry in its final form.  The wax pattern is then attached to a "sprue base" which is made of durable rubber.  The rubber base and the wax model are then placed into a metal flask and plaster is poured over the wax mould.

 

After the chunk of plaster has been allowed to dry it is then placed in a hot kiln. As temperatures rise, the wax within is melted and eradicated, hence the name "lost wax."  The result of this stage is a strong mould with a hollow opening in the shape of the original wax design.  In the kiln, the burnout times are anywhere from 5 - 12 hours. Still warm, the flask is then taken out of the kiln and placed in the centrifuge.

 

At this stage, bits of silver are ready to be melted. Sterling silver is an alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper. This combination allows for strength while preserving the ductility of the silver and the high precious metal content. 

 

Once the silver is almost entirely melted, a crucible will be heated. When the crucible will be red hot, it will be placed in the centrifuge and the silver will be poured into it.  The crucible sits tightly against the flask which holds the negative impression made by the burned-out wax pattern.  When the silver is completely liquefied, the centrifuge will start to spin very quickly forcing the liquid silver into the flask.  When the silver is cold, the whole flask, containing the plaster and silver jewelry items is then quenched in a bucket of cold water to dissolve the investment and to harden the silver.  After the silver and the plaster has been allowed to cool, the plaster is chipped away.  The original wax mould is gone, and the silver piece replaces it.

 

The piece is then cut off with a diamond cutoff wheel.  It is then grounded smooth and rubber-wheeled.  The piece is then buffed and cleaned. Sometimes, antiquing and dots of yellow gold are added to enhance the design.  The piece is then re-polished and cleaned. 

 

Videos

 
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Wax Carving
Installing the sprue and pouring the investment
Burning the wax
Preparing the silver bits
Melting the silver bits
Pouring the silver in the crucible
Placing the crucible it the centrifuge
Spinning and forcing the liquid metal into the flask
Dissolving the investment
Chipping the investment
The silver piece has replace the wax mould
Grounding and polishing
Final piece
 

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Dissolving the investment