What Is a Crucible Furnace?

A crucible furnace is a furnace specifically designed for use with crucibles, large containers of fire-resistant material used to hold products like metal and glass while they melt so they can be worked. Crucible production of a wide variety of products, from handmade crafts to industrial equipment, occurs around the world, and such furnaces are a key part of this process. A number of companies make crucible furnaces. Some focus on specialty applications while others make general use products for their customers.

The crucible furnace has a spacious interior made with a lining of refractory material like brick. Insulation and an outer casing maintain temperatures inside and make it safe to work around the furnace when the heating element is in operation. Gas or electric elements can be used for heating, and may raise internal temperatures very high, depending on the application. The operator places filled crucibles inside, seals the furnace, and fires it to melt these materials.

Typically the interior is configurable. This allows a technician to position shelves and racks in optimal positions for firing. The technician can move these around to accommodate crucibles and loads of various sizes, and to balance the contents. The goal is even, consistent heating of all items in the crucible furnace, and this requires careful effort to place items in optimal positions. Fans and vents can be used to promote air circulation and avoid the development of hot or cold spots inside the furnace that might interfere with firing.

Size can vary considerably. People like jewelers may work with a very small tabletop crucible furnace for their projects, while industrial furnaces can be huge. The device is usually programmable to allow the operator to set it on one of any number of cycles, or to develop a custom cycle. The program carefully controls temperatures as the crucible furnace warms up, fires, and cools down. These controls are critical for the protection of the materials inside, as well as for maintenance of the furnace itself, as refractory brick can be damaged by sudden temperature extremes.

Crucible furnace safety usually requires people to wear protective garments and eyewear when the device is in operation. Garments can prevent burns, while goggles keep the eyes safe from bright light as well as splashback. Technicians also receive training in handling emergencies, operating emergency stop buttons, and other issues. The furnace area may be locked and secured for additional safety.