A muffle furnace, also known as a retort furnace, is a piece of oven-type equipment that can reach high temperatures. It usually works by putting a high-temperature heating coil in an insulating material. The insulating material effectively acts as a muffle, preventing heat from escaping.

A Muffle furnace allows rapid high-temperature heating, recovery, and cooling in self-contained, energy-efficient cabinets. A muffle furnace separates the object to be heated from all byproducts of combustion from the heat source. In modern electrical furnaces, a radiation or convection energy applies heat to a chamber using a high-temperature heating coil inside insulated material. The insulating material effectively acts as a muffle, preventing heat from escaping

Muffle furnaces now use technology and design to achieve greater control of temperature uniformity and isolate heated materials from combustion contaminants. This makes muffle furnaces ideal for ashing samples, heat-treating applications, and materials research.

Industrial manufacturers or laboratory environments commonly use muffle furnaces for high-temperature applications. These applications include:

• Melting glass
• Creating enamel coatings
• Technical ceramics
• Soldering and brazing

Today, a muffle furnace is usually a front-loading box or tube design used for high-temperature applications such as melting glass, creating enamel coatings, technical ceramics or soldering and brazing. They are also used in many research facilities to determine what proportion of a sample is non-combustible and non-volatile (i.e. ash). Advances in materials for heating elements such as the molybdenum disilicide used in our “Rapid Temp” series of high temperature furnaces, can now produce working temperatures up to 1,800 degrees Celsius (3,272 degrees Fahrenheit) which facilitate more sophisticated metallurgical applications like debinding, sintering, and end to end processes in metal injection molding.

The term muffle furnace may also be used to describe another oven constructed on many of the same principles as the box-type kiln mentioned above, but takes the form of a long, wide, and thin hollow tube used in roll-to-roll manufacturing processes.

Both of the above-mentioned furnaces are usually heated to desired temperatures by conduction, convection, or blackbody radiation from electrical resistance heater elements.Therefore, there is (usually) no combustion involved in the temperature control of the system, which allows for much greater control of temperature uniformity and assures isolation of the material being heated from the byproducts of fuel combustion.