Wax replacement casting is used by major jewellers worldwide.
A process used to make multiple copies of the same piece of jewellery whereby an original masterpiece is made and then duplicated. The most common method used today is wax replacement casting.
The first step is to create the original masterpiece from which quantities will be duplicated. There are two main methods of doing this and it depends very much on the type of design to be created. The more traditional method is for a silversmith to craft the first piece entirely by hand. Using exactly the same tools and techniques that have been used for centuries, they carefully sculpture and assemble the piece following a sketch or photo from the designer. More recently, specialist computer aided design (CAD) software has been developed where a skilled computer operator turns the designers’ concepts into a three dimensional image. Then, using a very expensive specialised three dimensional printer (costing over £100,000), the design is printed out, not on paper but in a three dimensional resin. It takes the printer several hours to complete the task, but when finished you have a resin/plastic version of the ring from which duplications will be made.
The next step is to create a rubber mould of the design. When this is completed, you will have an inverse of the original design into which liquid wax is injected. Once the wax has cooled you then remove it from the rubber mould and repeat the injection process as many times as the number of pieces of jewellery you wish to make.
Once completed, a jeweller checks each piece and corrects any imperfections by adding, removing or remodelling the waxes. Next all of the waxes are attached to what is known as a “wax tree”.
After the tree is assembled it is placed inside a cylinder into which an investment (casting material) is poured. If you ever made plaster of Paris models as a child, this is a similar technique, however the investment is an incredibly fine powder. We have used hundreds of different investments over the years, but right now the powder that provides the smooth finish on our gold and silver designs is actually mined in Derbyshire and is then flown to our facilities in India. Once the investment hardens, it is then placed in an oven at a temperature of between 800 to 1100 degrees Fahrenheit, at which the wax melts and is allowed to run out of the bottom of the cylinder.
Now you are left with a cast where there is an empty space for each ring. Next the gold or silver is poured into the top of the flask and it flows into all of the space that was previously occupied by the wax. The machinery in which this takes place is becoming more and more advanced. Some use centrifugal force to ensure the metal flows evenly into every small detail (imagine even the tiny prongs need to be made), others create a vacuum and some even do both. The more advanced the machine, the better the finish of the jewellery, the better the porosity of the metal, and the more accurate the piece will be.
Once the metal is cooled, the flask is quenched and the investment removed. Next the silversmith or goldsmith detaches the jewellery from what is now a metal tree and starts to file and polish the jewellery. The remaining tree stump, which is either solid gold or silver, is then refined and used once again. When completely polished, the jewellery is ready to be handed to the gemstone setter to add the final gemstones.
As you can see, the lost wax injection method is very complex, with many steps involved. At every stage skilled operators and jewellers are required. The quality of equipment used, the brand of wax, the type of injection machine, the grade of investment powders, the type of ovens, the sophistication of the casting machine: all of these have a direct effect on the quality of jewellery produced. Whilst all of the highest-grade of equipment and consumables are very expensive, in the long run a jeweller who invests in the best should always see a good return on their outlay through the quality of the jewellery they create.
One interesting point is that this casting method still needs a lot of work to be completed by competent jewellers. It’s a jeweller who checks each piece of wax and improves the finish of it before it is assembled on to the wax tree. It is a jeweller who files, polishes and amends each piece after casting. It’s a jeweller who sets each gemstone in the final stages and of course it is a highly skilled lapidarist who cuts, facets and polishes the gemstones in the first place. I tend to refer to jewellery that is cast not as ‘hand made’, as this would suggest no machinery was used at all, but as “hand crafted”.
With the exception of “one of a kind” pieces, most rings, pendants and earrings are made this way today. Whilst the casting method is very efficient and flexible, it can obviously only cast one type of metal at a time. Therefore, when two metals are combined to make the same design, they are cast separately and then bonded together by the jeweller.
