Lost-Wax Casting
Lost-wax casting is an ancient method where a wax model is encased in a mould, melted away, and replaced with molten metal.
Lost wax casting, also called investment casting, is the technique behind most fine jewellery. A wax model of the piece is surrounded by a heat resistant material, the wax is melted and burned out to leave a hollow cavity, and molten metal is poured or drawn into that space. Humans have used the method for over five thousand years, and it still captures detail better than almost anything else.
How lost-wax casting works step by step
The process runs through a set sequence, and each stage matters to the final result.
- A wax model is made, by hand or from CAM, and checked for detail
- Wax models are attached to a central wax rod, or sprue, forming a tree
- The tree is placed in a flask and covered in liquid investment, a plaster-like slurry, which is left to set
- The flask goes into a kiln, where the wax melts and burns out completely, leaving a hollow mould
- Molten metal is cast into the cavity using vacuum or centrifugal force
- After cooling, the investment is broken away and the pieces are cut from the sprue for finishing
Why the trade still relies on it
Lost wax casting reproduces very fine detail, undercuts and delicate galleries that could not be machined directly in metal. That makes it ideal for intricate settings, filigree and sculptural forms.
It also scales. A tree can carry many pieces at once, and a rubber mould of a master lets a workshop produce identical waxes on demand, turning a single design into a repeatable product without losing quality.
Where it can go wrong
The method is unforgiving of shortcuts. If the wax is not fully burned out, residue spoils the surface. If the metal is too cool or the flask temperature is wrong, thin sections fail to fill and the piece comes out incomplete.
Porosity, cracking and rough surfaces usually trace back to temperature, investment quality or sprue placement, so experienced casters treat those variables carefully. Done well, the results are clean, dense and consistent from batch to batch.
- A wax model is invested, burned out, and replaced with molten metal
- Pieces are cast on a sprued tree, often many at once
- The method captures fine detail and undercuts machining cannot
- Rubber moulds of a master make the same design repeatable
- Burnout, temperature and sprueing decide casting quality
Lost-Wax Casting, in short.
How old is lost-wax casting?
It dates back more than five thousand years, with ancient examples found across many early cultures. The core idea, a sacrificed wax model replaced by metal, has barely changed, even as the tools around it have modernised.
What is investment in casting?
Investment is the plaster-like material poured around the wax tree. It sets hard, withstands kiln heat, and holds the exact negative shape of the piece once the wax is burned out.
Why is it called lost wax?
Because the wax model is lost during the process. It is melted and burned away inside the mould rather than removed intact, leaving the cavity that the metal fills.
Can many pieces be cast at once?
Yes. Wax models are attached to a central sprue to form a tree, so a single flask can cast dozens of pieces in one pour, which is why the method suits both one offs and small production runs.
Related terms
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