Casting Materials
The mould is a negative. The positive is what is cast in it.
| Material | Set | Character | Watch for |
|---|---|---|---|
| Plaster | Minutes | White, matt, fragile | Weak in tension; indoor only |
| Resin (polyester) | Minutes to hours | Hard, takes fillers | Styrene fumes; high heat |
| Resin (epoxy) | Hours | Stronger, clearer | Skin sensitiser; slower |
| Concrete / GRC | Hours to days | Heavy, weather-proof | Needs reinforcement |
| Wax | Minutes | Soft, remeltable | For bronze casting |
| Ceramic slip | Hours | Fired after casting | Shrinks; ceramic rules apply |
Two properties decide most material choices:
- Exotherm: resins release heat as they cure. Thick sections can overheat and crack the mould.
- Shrinkage: all casting materials contract. You must know the exact rate for precise work.
Slip casting is the ceramic process. Liquid clay fills a dry plaster mould. The plaster absorbs water, forming a solid clay wall before excess slip drains away. Wall thickness depends on how long the slip sits in the mould.
The Multiple
A reusable mould allows multiple copies. Once created, it changes the status of the artwork.
- An edition is a fixed number of casts declared in advance. It may include extra artist's proofs.
- An edition limit is a social convention. Only the artist's declaration stops further production.
- Posthumous casts are produced after an artist's death. They remain physically identical but lack direct oversight.
This highlights an ontological distinction in art theory:
- A carved marble is autographic. Its unique physical history constitutes the artwork.
- A cast bronze is allographic. Multiple casts can be equally authentic.
Common pitfall: assuming the first cast is the original. Every cast in an edition is equally authentic. An unauthorised cast differs only by the absence of the artist's decision.