Lost wax casting, also known as 'investment casting,' is the process by which a single metal object is cast from a wax model. It is a highly versatile process that achieves exceptionally detailed results. This guide will cover how to start lost wax casting and what you can create with the process.
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Lost wax casting builds a mold around a sacrificial wax model. After the mold investment is set, the wax is melted out and forms a cavity where the metal or glass flows in. Using this method of casting captures fine details in both metal and glass. This ancient method has been used since B.C. to visually capture the stories of ancient cultures and religions throughout history.
Lost wax casting is a 6,000-year-old process still used in both manufacturing and fine art. The precision and accuracy of the process have made it an ideal method for producing objects with thin walls, intricate details, and close tolerances. The process is used to create parts for transportation, agricultural, and medical industries, to name just a few. It can be used to create objects from simple to complex in various metals by casting an original wax model or pattern. The wax model makes an expendable mold that can only be used once in casting. This guide focuses on the lost wax casting process with metallic alloys. You can also use lost wax casting techniques to create cast glass objects. To learn more, head to our glass casting guide.
The basic lost wax casting process involves creating a pattern and a mold, then pouring molten metal into the mold. You will then extract the solid metal casting and finish your piece. This process is customizable for different types of metal casting, along with shapes, sizes, and more. The description below is based on smaller-scale casting processes, often used for jewelry. While essentially the same, in larger castings the mold material is made of Ceramic Shell (colloidal silica and various grades of silica), rather than plaster.
Create your desired design in wax before building a mold around it. This wax model can only be used once. After that, shape it with texturing tools, a soldering iron, and a heat gun. Many experienced wax sculptors swear by repurposing dental tools to sculpt and carve unique designs in wax effectively. Hollow out your wax model if possible.
When shaping your pattern, make sure you account for any anticipated shrinkage when the metal cools. Patterns may also be gated with sprues to allow the molten metal to flow into the mold. This is especially important if your design contains small intricate elements that may not fill with metal during the casting process.
You can make a mold using a combination of plaster and silica. Use a gram scale to measure each ingredient and mix equal parts by weight of plaster, silica, and water until the investment has the consistency of heavy cream. Plaster gives the mold support and silica has a high refractory, so it can withstand a lot of heat.
' When working with dry materials, make sure that your work area is well ventilated, and wear a respirator when working with dry investment.
The easiest way to melt the wax out of a small mold is in a microwave. First, remove any metal clamps you might have added to your mold, then prop it up on clay supports over a small container underneath to collect the wax. Heat in short bursts in the microwave until all of the wax has dripped into the small container. You can also burn out the wax in a kiln.
All metal castings are produced from either ferrous or non-ferrous alloys. Alloys are a mixture of elements that provide the best mechanical properties for the final cast's use. Ferrous alloys include steel, malleable iron, and gray iron. Non-ferrous alloys most commonly used in casting are aluminum, bronze, and copper. If you are working with precious metals in a jewelry studio, you may work with silver, copper, gold, and platinum. Less common, but especially spectacular, are metal castings with iron, which casts molten iron into a ceramic shell or resin-bonded sand mold.
Melting processes vary between alloys because each alloy will have a different melting temperature. Essentially, melting consists of placing the solid alloy in a crucible and heating it over an open flame for smaller projects or inside of a furnace for larger amounts.
Pour the molten metal into the mold cavity. If it is a small casting, you may simply pour from the crucible where the metal was heated directly into the mold. However, a larger casting may require a small team to support heating the metal inside a furnace and transferring the metal into a larger crucible or ladle before being poured into the mold.
' Make sure to follow all recommended safety guidance when pouring molten metal. Wear protective clothing, including natural fiber clothing, long pants and sleeves, insulated gloves, and safety goggles. Work in a well-ventilated space to avoid any risks from dangerous fumes. Ensure you have a chemical fire extinguisher nearby and keep your walkway between the furnace and the mold clear. Allow the mold to solidify before moving on to the next step.
When the metal has cooled and solidified, you can remove it from the mold. You will want to quench the plaster in water after the metal has solidified. The water will help break away the mold. If you cast it into a ceramic shell, you can break the mold and chip it away using the necessary equipment.
File and polish your solid metal cast! Finishing techniques include scrubbing away excess mold material in water, breaking off the casting gates with clippers for small objects, or even an angle grinder for large pieces. You can also choose to polish or patina your metalwork to give it color and dimension.
At The Crucible, you can learn to cast metals for small or large projects in different types of metallic alloys. The Crucible offers a wide variety of classes teaching lost wax casting and metalworking techniques. So whether you want to learn the fundamentals of casting or something more advanced, The Crucible has you covered.
In our Jewelry Department, you can cast small-scale silver and bronze objects from wax and organic objects. Our Foundry Department guides you in casting larger projects in bronze and aluminum using ceramic shell molds. Lost wax casting doesn't stop at casting metals'you can even learn to cast glass into molds in our Glass Casting and Coldworking Department.
Learn the ancient process of lost wax casting sculptural jewelry. Experimenting with different types of wax, you will carve, cast, and finish at least one small fetish, pendant, or ring in silver or bronze. Students are encouraged to bring in personal sketches and ideas.
Ceramic shell is a mold material used in the lost wax casting method. Learn basic wax-working techniques and explore basic metal finishing in this fascinating course. You will create a wax sculpture and build ceramic shell molds, transforming your original wax piece into bronze or aluminum.
This class is for people with metal casting experience who have completed waxes to cast. We can also accommodate 3-D printed PLA (best unpigmented). Students will prepare their patterns, gate them, build the ceramic shell mold, cast in either bronze or aluminum, destroy the mold, and remove the gates.
Bell Casting introduces participants to bell design and the lost wax foundry technique. In this class, you can design, cast, and finish a bell approximately six inches in diameter. This entry-level class provides a foundation for further exploration in this versatile foundry approach.
In Iron Casting, you will explore mold construction and preparation while building a sand mold with resin-bonded sand to cast your own iron sculpture. Learn the steps required to prepare the cupola for an iron pour. At the spectacular iron pour event, students prepare iron and coke charges, operate the cupola, and pour molten iron into their new mold.
In our Foundry, you can make your own stovetop waffle iron with a waffle pattern of your own design. We will make sand molds and use a cupola furnace to melt the iron. At the spectacular iron pour event, students prepare iron and coke charges, operate the cupola, and pour molten iron into their new mold.
In our Glass Casting & Coldworking Department, you can create a glass sculpture using the ancient technique of lost wax. In this class, you will learn wax sculpting techniques to create wax positives that are invested in a refractory material to create a mold. The mold is de-waxed to create a void that is filled with glass melted in a kiln. When cooled the refractory is divested and the wax positive is now glass.
It is best to start lost wax casting in an established casting studio with a professional instructor. Lost wax casting can involve more advanced equipment that can be costly to set up. The safest and least expensive way to start lost wax casting is in a public class. Once you have experience and a strong understanding of the process and tools involved, you may explore setting up a lost wax casting studio at home.
Lost-wax casting is a highly versatile technique and can be used to cast objects in gold, silver, brass, copper, bronze, and aluminum.
The most significant difference between the die and lost wax casting process is the mold material. Die casting uses a metal mold, which is a nonexpendable mold. Lost wax casting uses a mold made out of plaster or ceramic shell, an expendable mold. In the die casting process, molten metal is forced into a mold cavity with high pressure.
Microcrystalline wax is best for modeling because it is pliable and slightly sticky. In addition, it's medium-soft consistency makes it easy to work with. Paraffin wax can also be used for lost wax casting, but it is not ideal for modeling. Paraffin wax is best used as an additive to harden an already existing wax model. Different kinds of specialty wax can also be used. Each type of specialty wax has a specific purpose, such as carving, modeling, or patching, and requires knowledge of their different melting points.
3D printed jewelry patterns and cast metal rings.
Lost-wax casting is a metal casting technique for creating objects, from simple to complex, in a variety of metals (such as gold, silver, brass, or bronze) by casting an original model or pattern.
It is one of the oldest known metal-forming techniques dating back 6,000 years, but it is still widely used for producing jewelry, dentistry, and art. Its industrial form, investment casting, is a common way to create precision metal parts in engineering and manufacturing.
While traditionally associated with artisanal handcraft, creators can now transform the lost-wax casting process with digital design and 3D printing to simplify the workflow, save time, lower costs, and reshape the process for the 21st century.
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Read on to learn how digital technologies have revitalized the lost-wax casting method and what it means for professionals from jewelers to dentists and volume producers.
Patterns sprued to a casting tree.
Molten metal poured into the investment.
The lost-wax casting process can differ depending on the industry and application, but it generally consists of the following steps. Cast parts can be made from a wax model itself, called the direct method, or from replicas of the original wax model, called the indirect method. The direct method jumps from step one straight to step four.
Model-making: The artist carves a design out of wax. The size and complexity of the wax model are limited to the wax carver's skill and the capacity of their casting equipment.
Creating a mold: A caster then casts this model and polishes the casting to produce a 'master' pattern. The master model is used to make a wax mold out of rubber, which is heated and 'vulcanized' around the master casting to make a flexible wax mold.
Producing wax patterns: Molten wax is injected or sometimes poured into the rubber mold. This can be done over and over to make copies of the original design.
Assembling the wax pattern: Sprues are added to the wax copies and they're connected to create a tree-like structure, which provides paths for the molten wax to flow out and molten metal to later fill the cavity.
Applying investment materials: The wax tree is either dipped into a slurry of silica, or put into a flask and surrounded by the liquid investment plaster.
Burnout: After the investment material dries, the flask is placed upside down into a kiln, which melts the wax leaving a negative cavity in the shape of the original model.
Pouring: The investment mold is further heated in a kiln to reduce the temperature difference with the molten metal. Metal is melted and then poured, using gravity or vacuum pressure to pull the metal into the cavity.
Devesting: Once the molten metal has cooled somewhat, the investment mold is quenched in water to dissolve the refractory plaster and release the rough casting. The sprues are cut off and recycled, while the cast parts are cleaned up to remove signs of the casting process.
Finishing: The cast parts are filed, ground, machined, or sandblasted to achieve final geometry and surface finish. Where necessary, the cast parts are also heat-treated to enhance the mechanical properties of the material.
The cast tree after divesting.
The cast part finished by filing, grounding, and machining.
It's no exaggeration to state that lost-wax casting is as old as civilization itself. Artifacts like scepters, sculptures, and furniture made through lost-wax casting have been discovered as far afield as Israel, Vietnam, Nigeria, Nicaragua, and the Indus Valley. The very oldest known lost-wax-cast object, an amulet created by a society in the Indus Valley, is over 6,000 years old.
After centuries of use in the production of sculptural ornaments and in textile relief, lost-wax casting began to be supplanted by piece molding in 18th-century Europe. Parts of the process were adapted for investment casting to meet the needs of the growing industry in the 19th century.
In dentistry, lost-wax methods are used widely to create gold crowns, inlays, and onlays. The legacy of lost-wax casting, as such, remains well in evidence today.
Today, digital software tools and 3D printing augment lost-wax casting with the advantages of a digital design and manufacturing process.
Digitally Design Pattern
3D Print Pattern
Prepare For Casting
Make Mold and Burn Out Printed Parts
Cast Pattern
Polish and Finish the Part
With the digital workflow, designers use CAD software tools to create designs digitally and a professional 3D printer to produce 3D printed patterns that can then be cast in the mold. After burnout of the positive pattern, the process follows the same path as traditional investment casting.
Thanks to digital techniques, the need for time-intensive manual labor is greatly reduced and the design itself is easy to preserve, modify, and recreate when needed.
From engineers to jewelry makers, various professional fields are taking advantage of the new possibilities enabled by digital technologies for lost-wax casting.
One of lost-wax casting's first use cases was for producing jewelry and fine ornaments. But wax patterns for intricate jewelry are complicated to produce by hand, and in a world driven by high demand and fast fashion, it can be difficult for hand-crafted pieces to keep pace.
Jewelry designers can use jewelry CAD software tools to design jewelry pieces, making it easier to produce and fit complicated geometries that once required hours of meticulous labor to carve from wax.
Digital design, advanced materials, and affordable in-house resin 3D printers are now changing the way jewelry manufacturers and designers work in terms of concepting, prototyping, and producing.
Stereolithography 3D printing can reproduce complex features that'd be difficult to hand carve.
Jewelry designers can use jewelry CAD software tools to design jewelry pieces, making it easier to produce and fit complicated geometries that once required hours of meticulous labor to carve from wax.
Affordable industrial-quality 3D printers can create patterns rapidly that can be cast just like traditional wax. 3D printing offers an almost unlimited scope for geometric creativity in design. Thanks to a precisely controlled laser, extraordinary design details ' delicate filigrees, raised text, and detailed pavé stone settings ' can be captured with incredible sharpness.
The biggest barriers to adopting a digital workflow in jewelry are often digital design skills and training. However, newer cohorts of jewelry designers entering the industry are taught the foundations of traditional design along with jewelry CAD software and training on 3D printers, preparing them for the inevitable transition.
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Lost-wax casting and pressing restorations have been standard practice in dentistry for decades to fabricate inlays, onlays, crowns, ceramic'alloy crowns, all-ceramic crowns, partial denture frameworks, and other implant restorations.
Wax patterns are traditionally formed by hand on a working die of the tooth or an arch model that is based on a manual impression from the patient. The patterns are then sprued to a tree and burned out, following the traditional lost-wax casting workflow.
With digital technologies, dentists collect the patients' anatomy digitally using an intraoral scanner, or a lab scans a physical model or impression using a desktop scanner. The scan data gets imported into CAD software and the dental technician designs the desired restorations. The patterns can then be 3D printed out of a wax-like material, and cast or pressed using the traditional workflow.
Patterns for dental crowns, inlays, partial denture frameworks, and more can then be 3D printed out of a wax-like material, and cast or pressed using the traditional workflow.
In dentistry, digital design is also not much of a limitation, since the patient's anatomy comes from an impression. Dental CAD software tools make the design process simple, while 3D printing automates the manufacturing process of the patterns that traditionally requires an experienced technician and many manual steps.
Digital technologies with lost-wax casting combine the best of the analog and digital worlds and empower dental labs to produce highly accurate patterns, with a consistent and reliable digital workflow and easy-to-use machinery.
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For industries requiring mass-produced metal parts with a high level of dimensional accuracy, casting remains a cost-effective and highly capable manufacturing process, producing critical components for aerospace, automotive, and medical applications.
Traditionally, patterns for direct investment casting, the industrial form of lost-wax casting, are carved by hand or machined if the part doesn't need to be mass-produced. With 3D printing, engineers and foundries can directly create patterns to achieve shorter lead times and geometric freedom that exceeds the design for manufacturability (DFM) constraints of molding processes.
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This webinar will walk you through the methods by which several established foundries were able to cast metal parts using patterns 3D printed on Formlabs' 3D printers. Learn how foundries are cutting costs, reducing lead times, and improving the quality of their metal parts by integrating Formlabs' Clear Cast Resin and Materialise Magics' Lattice with traditional casting methods.
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This white paper presents the methods by which several established foundries were able to cast metal parts using 3D printed patterns produced by Formlabs' stereolithography (SLA) 3D printers.
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The evolution of the lost-wax casting process with digital tools proves that technology doesn't need to alienate us from the past. Employed correctly, these techniques can produce high-quality parts at scale ' from bespoke custom jewelry to mass-produced automotive parts. The result is a remarkable new degree of production efficiency and design freedom.
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