I'm Isla, the first female lost wax caster at Shetland Jewellery. I have worked at Shetland Jewellery for 5 years. I love doing the casting because I get to do the whole process from the very start to a complete finish as I'm also a jeweller at my bench. The whole casting process is very interesting and I'm very passionate about it.
Casting is a technique used in the creation of jewellery, allowing our jewellers to bring their intricate and unique designs to life. It is a process that involves pouring molten metal into a mould, which then solidifies to form the desired piece of jewellery. This method offers great flexibility and allows for the production of complex and detailed designs that may be challenging to achieve through traditional fabrication methods.
The process of casting jewellery involves several steps, including the creation of a rubber mould, wax model, burnout, and the casting of the metal.
Creation of the piece:
To begin the casting process, our jewellers create a prototype in silver from a sketch on paper, this is because we know how silver works best. This piece is called the master pattern. This piece has to be perfect with no flaws because every piece will be exactly the same.
To create a mould of the master pattern, we layer sheets of rubber; the master pattern is then placed in the centre of the rubber. We use a heated Vulcan Press that melts the rubber sheets around the shape of the master pattern. We then use a scalpel to cut the master pattern out of the rubber mould.
Now that we have our rubber mould, we use a wax injector to inject hot wax in to the rubber mould this now makes a wax mould that is an exact replica of the master pattern. We set up these waxes on a rubber base and put a stainless steel can around them.
This is a fine powder almost like plaster of Paris. The powder is mixed with water to create an almost paste solution, this is then poured into the can and around the wax models. The investment hardens and forms a mould, capturing the shape and detail of the wax model.
Once the investment has fully set, the can is placed in a kiln, and the wax is burned out overnight at 650 degrees leaving behind an empty cavity within the mould. This is called the lost wax casting process. The burnout process eliminates any remaining traces of the wax model, ensuring a clean and precise mould for casting.
With the investment mould prepared, the next step is to melt the chosen metal, such as gold, silver, or platinum, into a liquid form. We cast sterling silver 92.5%, all carats and colours of gold and 95% platinum. The metal grain is melted in a crucible then the molten metal is poured into the cavity holes in the investment mould through a small opening called a sprue which is like a feeder for the metal. We use a pressovac vacuum casting machine to do this. The metal fills the mould and takes the shape of the original wax model.
Once the metal has cooled and solidified the flask is quenched in a bath of cold water revealing the cast piece of jewellery.
We now take these castings to our bench and prepare each piece by hand. We will file and scrape the fronts and edges and solder on any fittings to make it function as a piece of jewellery for example earring studs, brooch fittings, cufflinks, tie slides etc.
We then take the pieces of jewellery to the polishing machine, we have four grades of polish starting from a rough abrasive to a fine jewellers rouge.
We now have our finished piece of jewellery, here is a Three Nornes brooch. The Three Nornes is Nordic mythology and was designed by Jack Rae and features the three fates Urd (past), Verdandi (present) and Skuld (future). These three ladies transformed themselves into swans for ease of travel. Its one of my favourite ranges we make!