Lost-wax casting is a metal casting method used to create objects from very simple shapes to very detailed designs using various metals such as gold, silver, brass, or bronze. The process works by creating an original model or pattern and then casting the metal around it.
This technique is one of the oldest ways of shaping metal known to mankind, dating back about 6,000 years. Even today, it is widely used in jewelry making, dentistry, and art production. In modern industries, it is also known as investment casting and is used to create precise metal parts for engineering and mass production.
In the past, lost-wax casting was mostly done by hand, but today digital design tools and 3D printing have transformed the process. These modern technologies help manufacturers work faster, reduce waste, reduce costs, and make the method more suitable for today’s production needs.
History
Historical records show that 2,000 years ago, ancient Egyptians and Chinese craftsmen used the lost wax method. Later, the Aztecs, Maya, and several African tribes also practiced the technique.
Many precious metal artifacts displayed in museums today were made using this casting style. A Florentine goldsmith named Benvenuto Cellini helped refine the technique, and later Carl Faberge created highly detailed jewelry for the Russian Tsar, bringing renewed attention to the craft after it had almost fallen into obscurity.
What is lost wax casting?
Lost wax casting, sometimes called sire perdue, is an ancient technique in which metal objects are created using a wax model. The wax is shaped into a design and then replaced with metal. Over time, this method has been used not only for jewelry but also for sculptures and decorative objects. One of the biggest advantages of lost wax casting is that the same design can be replicated over and over again. The most commonly used metals include silver, gold, brass, and bronze, making it a great option for many jewelry projects.
What is the lost wax process used for?
Lost wax casting is a 6,000-year-old technique that is still important in both art and manufacturing today. Because this process allows for excellent precision and fine detail, it is suitable for creating thin objects and parts that require precise measurements. Industries such as transportation, agriculture, and medical manufacturing use this process to produce reliable components. It allows creators to create objects from simple shapes to complex designs using many types of metals. The wax model creates a temporary mold that is used only once during casting. While this guide focuses on metal casting, similar techniques can also be used for glass casting projects.
What is the lost wax casting process for jewelry? Step-by-Step
Would you like to try it yourself? Follow these basic steps of the lost wax casting process using a silver ring as an example:
- Start by cutting the shape of the ring from a tube of wax. Draw the design onto the wax using a scribe so you know where to make the first cut.
- Next, shape the wax using an engraving file until you have the desired design. Remember that wax can be made very thin because silver is about 11 times heavier than wax.
- Once shaped, attach a sprue of wax to the ring. Gently heat the sprue over a flame until it starts to melt slightly, then quickly place it on the thickest part of the ring.
- Weigh the wax ring and note the weight. To calculate the amount of silver needed, multiply the weight of the wax by 11 and add 10 grams for the sprue.
- Place the ring and sprue in the bottom of the flask, leaving at least 5 mm of space between the ring and the edges of the flask.
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Now the project moves on to the investment phase:
- Attach the flask to the rubber base and make sure everything is secure. Fill the flask with water to about 5 mm from the top, then pour that water into the rubber bowl.
- Measure out the investment powder and sprinkle it slowly into the water. The powder will sink at first and then float once enough water is added.
- Mix the solution for about 10 minutes to remove air bubbles, but do not overmix or it will become too thick.
- Place the bowl on a vibrating plate and hold it firmly so that the bubbles rise to the surface. Gently press down on the bowl as you pour the mixture into the flask.
- Place the flask on a vibrating table for about a minute to release trapped air.
- Allow the flask to harden overnight, then remove the rubber base to remove the wax sprue.
- Place the flask upside down in the kiln to melt the wax. Heat it to between 150-200°C for an hour, then increase it to 400°C for 1.5 hours, and finally to 720°C for another hour. These temperature stages completely remove the wax and harden the mold.
Now comes the final stage – centrifugal casting:
- Place the measured silver in the crucible, remove any solder or large scraps. Sprinkle some powdered flux on top and add an additional 10 grams of silver for the sprue.
- Wearing protective gloves, remove the hot flask using steel tongs, and place it in the centrifugal casting machine. Make sure it is securely fastened.
- Allow the metal to melt completely while you prepare the machine.
- Check that the metal is smooth without lumps, then start the machine, making sure that nothing is blocking the rotating arm.
- When the rotation stops and the flask changes from red to black, carefully remove it and place it in a bucket of cold water. Gently move it until the investment breaks and the metal casting is visible.
Finally, clean the casting using a pickling solution and clean off any remaining material. Cut the sprue with a jeweler’s saw, then file and polish the ring. You can keep it as a unique piece or make a rubber mold to reproduce it later.
Further Reading: Gold Bonded Jewellery Guide: Everything You Need to Know
FAQs
Q1. Can I do lost wax casting at home?
It is best to start learning lost wax casting in a professional studio with an experienced instructor. This process requires specialized equipment and tools that can be expensive and sometimes unsafe for beginners. Taking a class is usually the safest and most affordable way to get started. Once you have enough experience, you can consider building a small setup at home.
Q2. What metals can you use for lost wax casting?
Lost wax casting works with many metals, including gold, silver, brass, copper, bronze, and aluminum.
Q3. What is the difference between lost wax casting and die casting?
The main difference is the type of mold. Die casting uses reusable metal molds, while lost wax casting uses plaster or ceramic molds that break after a single use. In die casting, molten metal is forced into a mold under high pressure.
