Metal Casting: Lost Wax VS Sand Casting

Have you always dreamed of creating a metal jewelry piece from scratch, but felt that the technique was far too complicated and that you would need the help of an experienced jeweler to cast the metal?

That is partly true. But what if you could create your own jewelry independently, without necessarily relying on a professional casting workshop?

In this article, we will not only explain how the process works, but also guide you through the materials and tools you need to choose, step by step, to achieve excellent results even in a small home studio.

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Lost wax and Sand Casting, what does it mean?

These are two different techniques used to obtain a metal jewellery, and both start from the processing of a model made of wax.

The lost wax technique is one of the oldest and most refined methods for creating jewellery. It originated with the first metallurgical civilisations over 6000 years ago. The basic process has remained unchanged over the centuries and consists of creating a model in wax that will be melted and replaced by molten metal through a casting process in a refractory mould. It is a technique that allows for great creative freedom and remarkable precision in details.

The technique with sand casting, on the other hand, also allows for the same result, but without losing the work created with wax. This technique is more straightforward, but less precise. It is not suitable for intricate carvings and is recommended for small productions.

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First important step: choosing the wax and tools to shape it

It is essential to choose the right form of wax based on the work you are planning to carry out:

ROUND WITH CENTRAL HOLE - for rings with a round profile and central hole.

ROUND WITH ECCENTRIC HOLE - for rings with a round profile and eccentric hole, ideal for inserting a setting.

SOLID ROUND - suitable for multiple uses, particularly pendants and small rings.

SHIELD WITH HOLE - for signet rings, already shaped to minimise material removal.

PLATES AND SHEETS - designed for versatile sculpting, perfect for layering and precise details.

ROUND PROFILES - used for modelling, sprue.

SEMI-ROUND PROFILES - suitable for profiles and edging.

These forms can be found in various colours, which do not change anything about their properties; they are coloured simply because during their particular and meticulous processing it might be tiring for the eyes to use the same colour all the time.

Only for the profiles do the colours have a specific function:

BLUE - medium hardness, easy to sculpt

GREEN - harder wax, for precise details and structural parts

A good manual piercing tool and excellent blades will allow you to cut precisely the part you need.

You can then proceed to work using the wax tube with shield and hole and a hot engraving tool to shape it and melt the parts of wax to be sculpted.

To enlarge the holes of the wax rounds, which you will need for creating the rings, you can use the mandrel with blade. A single tool that helps you increase the size of the ring by gradually cutting away the unnecessary wax parts.

Always remember that the prototype created must be exactly like the final result you want to achieve, both in details and dimensions.

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Lost Wax Technique

You have finally managed to shape your wax jewellery, and now? For the lost wax technique, you need to create more!

This method is used for working on multiple pieces simultaneously, so that in a single pour of metal you can obtain many, thus concentrating a greater production in the shortest possible time.

Then add to each piece, at its base, a sprue, which is nothing more than a filament of wax that will allow you to mount the prototypes on a central axis (sprue tree), also made of wax, which will serve as a conduit for the molten metal.

This cluster is then fixed to a rubber base and then covered with the perforated cylinder that will serve as a container for the plaster to be poured inside. The holes present are useful during the firing phase for proper air evacuation, but to be filled it must be sealed beforehand. You can choose to close it with paper and tape or with different types of films; the important thing is that it adheres well to avoid the plaster leaking out.

The Plaster

It is a special refractory material specifically designed for use with molten metals, thus heat-resistant. The casting plaster is suitable for pouring non-ferrous metals, such as silver, gold, and brass. When mixed with water, it is important to avoid incorporating air bubbles, so the use of a mixer or a vacuum pump is always recommended.

It is poured inside the cylinder and after it dries, both the rubber base and the casing created around the cylinder are removed. It is now possible to proceed to the melting of the wax inside the oven to obtain the shell where the molten metal will then be poured.

The Kiln

The cylinder is placed inside an oven specifically designed for the lost wax technique. In the firing chamber, there is a perforated grid suitable for inserting the cylinders, and just below it, a collection basin for the wax that will melt during firing.

The wax in the cylinder will completely melt, leaving a void imprint in the plaster: the mould is now ready to receive the pour of molten metal.

Metal Melting

Let's prepare the metal.

This process takes place in a small kiln that contains a crucible. Here, the metal to be melted is inserted, and the melting temperature suitable for the type of metal chosen is set.

Once this process is completed, using a special crucible tongs, the metal is poured into the plaster mould while it is still hot, filling all the spaces left by the melted wax. To ensure full insertion into the cavities, a centrifuge or a vacuum machine is often used.

Extraction and Finishing

After cooling, the cylinder is immersed in hot water at 45°C to dissolve the refractory plaster and extract the cluster that has now completely turned to metal.

Washing is performed to clean the entire structure from plaster, and finally, the obtained pieces are separated one by one. The central tree, which has also turned to metal, is material that can be refused and reused.

The finishing process of the jewellery begins: filing, polishing, tumbling, and hand finishing, and where possible, stones can be added, engravings can be created, or details can be coloured with the appropriate glazes.

Sand Casting Technique

There is also another technique for working with molten metal that still requires the creation of a wax model as a starting project. The created model will not be melted, but used to create a mould. It is a process that allows for the creation of one piece of jewellery at a time and is not suitable for reproducing intricate and detailed features.

Let's see how it works and all the materials you need.

Preparing the Frame

Then imprint the prototype so that it is immersed in the sand for half of its volume and dust the surface with talcum powder. Then join the second part of the frame, which is still empty, and add more red sand to fill it, always pounding with the hammer. This process will create a sort of mould in the sand.

Now separate the two parts, remove the wax prototype, and create the heat escape channels and a larger channel that you will need for pouring the metal into the mould (this corresponding to the one already present in the mould).

Reassemble the two parts of the frame, and you are now ready to pour the liquid metal inside. For this process, especially if you are working on a single piece, you can melt directly with a torch using crucible and tongs. Remember to prepare the crucible with borax before proceeding with the melting.

Let it cool and then open the frame to extract the piece.

Then proceed to finish it as indicated for the previous process.

Final Suggestions and Summary Table

• Always wear appropriate protective gloves and heat-resistant ones.
• Rely on heat-resistant surfaces.
• Use a different crucible for each type of metal you melt.