Lost-wax casting is a technique that’s been used for over 5,000 years. It’s one of the most reliable methods for sculpting metals like bronze, silver and gold into three-dimensional objects.
So why don’t you see more people using it? Well, lost-wax casting is a very involved process that takes a lot of time and patience (and money).
This article will walk you through all the steps involved with lost-wax casting: how to design your sculpture, create wax models and ceramic molds, pour molten metal into your mold…and all the other steps in between!
| Key Takeaways |
|---|
| 1. Lost wax casting is a popular method for creating bronze sculptures. |
| 2. The process involves creating a wax model, making a mold, melting out the wax, and pouring in molten metal to create the final product. |
| 3. Lost wax casting can be used with a variety of materials, including bronze, aluminum, silver, and gold. |
| 4. The process can take several weeks and requires multiple stages of preparation. |
| 5. Lost wax casting is a versatile process that allows for great detail and precision in the final product. |
Design The Sculpture
You’ll have to design your sculpture in your head, on paper or on a computer.
You can also create a maquette of the sculpture in clay, wax or bronze. This is called “modeling up” and it allows you to refine your design before investing time and energy into making it permanent.
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Create The Wax Model
The first step in creating your cast is to create a wax model. To do this, you’ll need to get some clay and start shaping it into the rough shape of your original object like a sculpture or a ring. You can use any material you want to make this mold, but we recommend using something that’s easy on the hands (clay is good) and flexible enough to be removed later (softer plastics such as polyurethane work well).
Once you have your model made with clay, refine it by pouring hot wax into its cavity. This creates what’s known as an “investment mold,” which will then be used as the basis for making each individual piece of bronze.
After pouring in the investment, add plaster overtop of everything—this creates more detail and increases strength for when you go about removing it all later on. Then, let everything dry until the mold hardens up completely before taking it out so that you can put them together one last time before all their parts are ready!
| Technique | Description |
|---|---|
| Carving | Sculptors use various tools to carve or whittle a block of wax into the desired shape of the object to be cast. |
| Modeling | Artisans use soft wax to mold by hand, often building up the wax in layers to create the finished form. |
| 3D Printing | Digital 3D models are used to create wax models using a computer-controlled printer that deposits layers of wax to build up the final shape. |
| Injection | Molten wax is injected into a mold cavity and allowed to cool, creating a solid wax part. |
| Assembly | Multiple wax components are created separately and then joined together with wax adhesive to form the final wax model. |
Note: The techniques listed above are not exhaustive, and there may be variations or combinations of these techniques used to create the wax model for lost wax casting. The choice of technique will depend on various factors, including the desired final product, available materials, and experience of the sculptor or artisan.
Build The Ceramic Shell
The next step is to build your ceramic shell. Clay is the material used for this, and it can be made from any kind of clay; however, you want to make sure that the clay is strong enough to withstand the heat of your kiln (as opposed to air drying or oil fired clays which shrink when they are fired).
You also want a smooth, even surface so that there aren’t any cracks or gaps where water can collect in your mold during casting.
Finally, don’t use previously fired clay because this will cause problems with how well your piece comes out during casting.
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Fire The Ceramic Shell
Once the ceramic shell is formed, it needs to be fired. This firing process will help the clay harden and take on a shiny, white appearance. In order to get your ceramic shell to this state, it must first be heated up in an oxidizing environment (as opposed to a reducing one).
The temperature of the furnace should be between 2100 and 2200 degrees Fahrenheit, and you’ll want to set your kiln up so that it can maintain this temperature for about 4 hours.
It’s best not to have any more than two hours between layers of ceramic shells when they’re going into the kiln; otherwise they won’t fuse together properly during firing.
Melt Out Wax
The next step is to melt out the wax. This can be done using a propane torch and a double boiler (or even just a pot of boiling water). You should also make sure that you’re using as little wax at once as possible, so it doesn’t overheat and burn.
If you’re going to use a propane torch, be careful when doing so! It’s important that your work area is well-ventilated and there are no flammable materials in the vicinity (such as other pieces of artwork).
Also keep an eye on where your torch flame is pointing: if it comes too close to your sculpture or tools, they could catch fire!
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Pour Bronze Into Shell
Once your wax model is finished, it’s time to make the final plaster mold. Mix together a batch of plaster and water, using about 1 part plaster to 3 parts water for the outer shell.
Pour this mixture into the mold box, making sure that it comes up to cover the top edges of all four sides by at least ⅛-inch (3 mm).
Pour more plaster around the sides until there are no gaps between them and no air bubbles appear in any part of the surface. Let dry overnight.
| Method | Description |
|---|---|
| Vacuum Casting | Uses a vacuum chamber to remove air from the shell mold, creating a vacuum-tight seal. Molten bronze is then poured into the mold, filling the negative space left by the wax model. |
| Centrifugal Casting | Rotates the mold at high speeds while molten bronze is poured in, distributing the metal evenly and creating a smooth surface finish. |
| Induction Casting | Uses an electrically-generated magnetic field to heat the molten bronze, which is then poured into the shell mold. This method allows for precise temperature control and reduces oxidation. |
| Continuous Casting | A continuous stream of bronze is poured into the mold through a narrow opening, creating a smooth, uniform surface. |
| Gravity Casting | Molten bronze is poured into the mold using gravity, filling the negative space left by the wax model. This method is often used for smaller sculptures or where fine detail is not required. |
Note: The above bronze pouring methods are some of the most commonly-used techniques in shell casting, but there are variations and combinations of these techniques used depending on the desired outcome, the type of bronze being used, and size of the sculpture.
Crack Shell With Maul
You can use a maul to break the shell. To do this, hold the maul in both hands and strike the inside of the shell with it.
You might have to repeat this a few times until you get through all of it. If that doesn’t work, try using an ax or other heavy-duty tool like a chisel or shovel to break up the hard parts (like sandstone).
If you are having trouble removing any wax from your mold after you put everything together, try soaking them in water for about 24 hours before trying again—this will help loosen things up so they’ll be easier to remove
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Chase And Weld Your Sculpture
After your sculpture is finished, it’s time to chase and weld. Chasing is the process of cutting, grinding and polishing the surface of the bronze.
The goal here is to create a smooth surface that will facilitate molding and casting in molten metal.
Welding involves joining two or more pieces of metal together so they become one piece; this technique is often used in conjunction with chasing because it can strengthen weak areas on your sculpture.
Chasing and welding are both labor-intensive processes that require precision and skill, so if you don’t feel comfortable doing them yourself (and let’s face it who does?), consider hiring an expert caster to do this work for you.
If you’d like to learn more about chiseling techniques or how to get started as a caster yourself, check out these resources:
Refine The Surface Of Your Cast Sculpture
The last step in the process of lost-wax casting is refining your bronze sculpture. You can use a variety of tools to do this, including sandpaper and polishing wheels, but if you’re looking for a more professional finish, consider using a polishing compound or cloth.
If you want a deeper shine than hand polishing can provide, try using an electric buffing wheel as well!
| Technique | Description |
|---|---|
| Sandblasting | Uses abrasive particles to etch the surface of the sculpture and create a matte finish. |
| Polishing | Buffs the surface of the sculpture to a smooth and shiny finish using a polishing wheel and compound. |
| Patination | Applies a chemical solution to the surface of the sculpture to create a unique color and finish. |
| Burnishing | Uses a hard, smooth object to rub and compress the surface of the sculpture, creating a shiny finish. |
| Sanding | Refines the surface of the sculpture using sandpaper or abrasive pads of increasing fineness to achieve a desired level of smoothness. |
Note: The techniques listed above are not exhaustive and there may be variations or combinations of these techniques that are used to refine the surface of a cast sculpture. The choice of technique will depend on the desired end result as well as the material and size of the sculpture.
Apply Patina To Your Sculpture
Now it’s time to apply the patina. Patina is a greenish-black coating that gives bronze its classic, antique look. It can also add rustic texture and grime if you want to make your sculpture look more realistic.
When applying patina, use a cloth or soft brush and rub it gently over the surface of your sculpture in layers until you get the result you’re after.
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Polish Your Sculpture By Hand With Jeweler’s Rouge
Once your sculpture is finished, you will want to polish it so that it looks clean and smooth. There are a number of different ways to do this, but here are some of the most common:
Use a polishing cloth to rub over the entire sculpture. This will give your work a high-gloss finish and remove any remaining fingerprints or smudges. Be sure not to use too much pressure while doing this; if you keep rubbing too hard on one area, you may scratch off some of the wax coating!
Use an electric buffing machine or hand drill with a polishing bit attachment on the end of it in order to get rid of any remaining imperfections in the surface texture (if any exist).
This is known as burnishing and can be done by hand or with machinery depending on how big/heavy your sculpture is and whether or not you’re looking for something more professional looking than just putting some elbow grease into getting rid of those pesky marks from handling it earlier
Conclusion
Casting is a process that’s been around for centuries, and it still has a lot of uses today. They are able to create an exact copy of something by pouring molten material (like wax, ceramic or metal) into a mold which retains the shape of the original object.
We’re going to take you through all steps involved in creating your own bronze sculpture from clay using this process!
Further Reading
For further reading on the topic of lost wax casting and sculpture, check out the following resources:
The Crucible Guide to Lost Wax Casting: The Crucible is a nonprofit arts and education center that offers classes and workshops in a variety of art forms, including metalworking. This guide provides a detailed explanation of the lost wax casting process.
Go Bronze: From Clay to Bronze: Go Bronze is a website dedicated to promoting bronze sculpture and educating the public about the art form. This page explains the lost wax casting process and offers step-by-step instructions.
An Encyclopedic Guide to Making Bronze Statues with John Brown: The Gnomon Workshop is a provider of professional training for artists in the entertainment and design industries. This tutorial, led by sculptor John Brown, covers the entire process of making a bronze statue.
FAQs
What is lost wax casting?
Lost wax casting is a casting process in which a wax model is coated in a refractory material, such as plaster or ceramic, and then heated to melt the wax out of the mold. Molten metal is then poured into the mold to create a final product.
What materials can be used in lost wax casting?
Lost wax casting can be used with a variety of materials, including bronze, aluminum, silver, and gold. The choice of material will depend on the desired end product and the casting process being used.
How long does the lost wax casting process take?
The lost wax casting process can take several weeks, depending on the size and complexity of the final product. It involves multiple stages, including creating a wax model, creating a mold, melting out the wax, pouring in the molten metal, and finishing the final product.
What are some common uses of lost wax casting?
Lost wax casting can be used to create a wide range of products, including sculpture, jewelry, and industrial components. It is especially popular in the art world for creating bronze sculpture.
What are some advantages of lost wax casting?
Lost wax casting allows for great detail and precision in the final product, as well as the ability to create complex shapes and forms. It is also a versatile process that can be used with a variety of materials and applications.
Hellen James is the creator of Unified Crafts and has been crafting since she was a kid accompanied by her mom to the craft store, where she was free to choose whatever ignited her imagination.
