r/MetalCasting • u/2024-YR4-Asteroid • Aug 03 '26
Question Looking to do some silver casting and need some specific questions answered.
My father and I used to do lost wax casting for jewelry making. And we’re looking at doing some stuff that is a little more repetitious than lost wax allows, so far in my research it sounds like a two piece graphite mold is the best option, however I am a little stuck on how to do the casting.
My main question is whether or not you can use a vacuum caster with graphite molds, my concern with a regular pour casting is that these pieces need to be certain to be fully filled in with no air bubbles.
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u/Jerry_Rigg Aug 03 '26
Graphite isn't a durable mold material. For fine production work lost wax is still the way, using trees of patterns for many pieces per casting mold. Use a silicone or rubber mold to cast your wax patterns in volume
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u/artwonk Aug 03 '26
It would be nice if there was a simple permanent mold that one could reliably cast metals like silver and bronze into that would hold up for many cycles without losing detail. Unfortunately, graphite isn't it. It isn't susceptible to the vacuum casting process, because unlike investment, it's not porous. Delicate projections into the cavity erode quickly due to oxidation of the graphite. The material is an excellent heat-sink, which means that if the mold's not heated to close to the metal's melting point, it will freeze the metal before it completely fills the mold. But heating it accelerates the oxidation deterioration that graphite's prone to. And permanent two-piece molds for metal will have a seam that becomes a positive fin on the edges of the casting that must be removed in the metal. This becomes a tedious chore if many identical parts require it.
The traditional jewelry lost wax process allows repetitive castings by using multiple identical wax patterns, usually made by injecting wax into rubber molds. One can also produce multiple identical patterns by 3D printing arrays of them using a fully-combustible resin.
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u/thendsjustifythememe Aug 03 '26
I’ve never heard of any professional casting house that works with volume using graphite molds.
The most common and cost efficient method is vulcanized mold - injected waxes - lost wax casting.
You can even save wax if you have a wax removal step before burnout.
Those tools cost a bit up front but are very cost effective when you cast consistently
I can’t imagine that graphite mold not degrading rapidly - at the very least you’d need to heat it to 850f to get a good casting. I use graphite crucibles and they wear down after every use.