So, how does the casting process really work?
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Understanding the lost-wax casting process
Lost wax casting, also known as investment casting, is a traditional technique that has been used since The Egyptians to create intricate and detailed jewellery and other small metal items. This process allows manufacturers, jewellers and makers to produce precise and high-quality pieces, whether for bespoke designs or larger production runs. The art of casting has since moved on to the science of casting giving us precise control over all of the stages in this fascinating process. Here's how it works:
1. Creating the wax model
The lost wax casting process begins with the creation of a wax model. This is an exact replica of your design in wax. It can be hand-carved, produced using CAD (Computer-Aided Design) and CAM (Computer-Aided Manufacturing) technology or, more often than not, by injecting wax into a silicone rubber mould of your design. These all ensure exceptional detail and accuracy.
2. Making the plaster mould
Once the wax model is complete, it is encased in a special investment plaster to create a plaster mould, called a flask. This material is incredibly high definition, allowing it to capture every detail of the wax model. After the mould has dried and hardened, it is heated in a kiln, which melts and drains the wax, leaving behind a cavity in the shape of your design. The heating continues upwards to 740°C converting the plaster to a basic, tough ceramic. This stage is crucial, as it forms the hollow for the molten metal. There could be up to 200 items in each flask!
3. Pouring the metal
The mould is then cooled to the correct temperature to prepare it for casting. The chosen metal alloy, such as gold, silver, or brass, is melted in a crucible under a nitrogen cover and at the precise temperature (to the degree!) poured into the mould. The high temperature ensures that the metal flows smoothly into all the fine details of the cavity. We give the metal a wee shove with 40psi of nitrogen. Once filled, the mould is left to cool and solidify.
4. Revealing the casting
After the metal has cooled, the ceramic mould is quenched to reveal the metal casting. This initial casting is still attached to a central core via sprues. These are now snipped off and meticulously cleaned by burnishing in pin polishers. These are now ready for quality inspection before dispatch to you unless...
5. ...you require finishing services?
We have various stages of finishing services available starting with removing sprues and readying the insides of rings and bangles for polishing. On top of this we can offer further stages of finishing - soldering jump rings, ear posts right through to fully polished items.