Lost wax technique: Nicholas explains how it works.
Working in Wax
For centuries a method of producing jewellery called lost wax has been used. It is a process that begins with a model made from wax and ends up with the model being cast in metal. I have always loved using the process – I use it a lot when making some of my bolder and more artistic pieces.
To explain: I carve a wax model of the item I wish to produce (in this case, the PIKE 2016 Christmas Collection shape) in its exact form out of jeweller’s wax, which is available in a number of strengths and colours from hard through to soft.
They have slightly different uses and I liken them to candle wax with plastic added – malleable and carve-able without being sticky. I tend to use the hard green wax,
and I use a number of things to carve and shape the wax – saws, woodcarving tools, blades, files and emery paper, and often as a final finish I pass the model through an open flame which gives it a smoother surface. This helps to give a superior cast surface and lessens the finishing time.
Once the model is finished it is secured to a ‘button’ or base of wax shaped like a cone with the broader part of the cone forming the base and a point at the top to which the wax model is attached. The model and cone are then enclosed in a hollow metal tube which sits down over the model and cone with space all around it.
An ‘investment’ similar to plaster of Paris is poured in around the cone and model and left to set. During the setting process, the whole tube is vibrated to release any bubbles that may have formed on the wax model inside. The reason for removing them is that it prevents unwanted solid metal spheres appearing on the finished cast surface.
Once the plaster is set, the entire tube and the wax inside are heated up in a kiln until the wax model and wax cone are burnt away leaving a cavity where the model and cone were: this is where the term ’lost wax’ originated.
The cone shaped cavity now becomes a funnel through which the molten metal is forced into the hot plaster mould, and the metal flows into the cavity and becomes an exact replica of the model I carved.
These days the molten metal is assisted by centrifugal or vacuum force. In earlier times, the molten metal was poured in and relied on gravity to force its way into the mould. Often the force was not powerful enough, so only some parts of the item cast successfully and the whole process had to be repeated. Today’s technology has allowed a much better result.
Once the metal and plaster have cooled the plaster is broken away revealing the cast metal item and cone.
The cone is then cut off and all that I am left to do is lightly file away where the cone was attached, file the surface of the item to remove mould marks, then emery and polish it to the required finish. Jewellery item completed!
Lost wax is a process which allows me to produce large items which would be difficult or impossible to achieve by hand. It also lends itself to designs which require certain surface textures for instance bark or molten appearances.
These can be created by hand by filing and shaping metal, but the lost wax method tends to replicate them more effectively. I also love the process as it is much easier to make changes in wax due to its soft nature, adding or taking away areas until the piece is just right. I can even bed gemstones into wax so once the piece is cast all that is required is finishing of the metal surface and setting of the gems.
If I want to make more than one of the item, there is an additional process that is performed where the metal item is moulded within a rubber mould, which allows the casting process to be repeated over and over. But more about this another time.
If you would like more information on the lost wax process, you are welcome to give me a call and I would be happy to describe it more fully and show examples of the things I have discussed.
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