Designing, creating and making gold jewellery is a time consuming process and requires craftsmanship. No matter how many carats the jewellery weighs for, the process will always be the same. The first thing you do is start off with a design and then move on to carving a wax model of the same. Different types of tools and techniques are used to create the wax model: steel wax carvers, files, hand gravers, burs, drills, heat etc. The wax is then ready for investing.
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Once, the wax model is ready, the next step is to invest. This requires the goldsmith to attach a sprue to the wax. The sprue serves as a channel for melting wax to escape during burn-out and later for molten gold to enter during casting. An investment flask is attached to the sprued wax which is attached to a round rubber base.
The process of investment begins as a dry fine white powder, a texture similar to that of Plaster-of-Paris. It is formulated to withstand high temperatures and hold great details during casting. Water is added to the investment to create slurry which is similar in consistency as that of a cake batter.
At this point, the investment needs to be free of bubbles. This can be done by placing the investment slurry in a vacuum where the air is drawn out. This process is called debubblizing. The wax is completely surrounded by a flask in to which the slurry is poured slowly. The flask is then placed into the vacuum chamber to make sure that there are no air pockets attached to the model that would corrupt the casting.
Once the investment hardens up, the rubber base is removed and the flask goes into the burn-out oven. The burn-out takes hours at a high temperature until the wax is eliminated completely. Once the burn-out is complete, only the hollow replica of an original wax carving remains inside the flask.
Now the mold is ready for casting. A casting machine holds the flask as the gold is melted in a crucible using a torch. The molten gold is thrown centrifugally into the hollow mold at the proper casting temperature and is held there until it solidifies completely.
The investment is then separated from the cast piece and only the rough casting remains. The casting only requires polish and clean up and the gold jewellery making process is complete.
