Muffle furnace

[2] Today, a muffle furnace is often a front-loading box-type oven or kiln for high-temperature applications such as fusing glass, creating enamel coatings, ceramics and soldering and brazing articles.

Some models incorporate programmable digital controllers, allowing automatic execution of ramping, soaking, and sintering steps.

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.

[citation needed] Both of the above-mentioned furnaces are usually heated to desired temperatures by conduction, convection, or blackbody radiation from electrical resistance heater elements.

Like other types of muffle furnaces, the design isolates the objects from the flames producing the heat (with electricity this is not so important).

An Automatic Oil Muffle Furnace, circa 1910. Petroleum is contained in tank A, and is kept under pressure by pumping at intervals with the wooden handle, so that when the valve B is opened, the oil is vaporized by passing through a heating coil at the furnace entrance, and when ignited burns fiercely as a gas flame. This passes into the furnace through the two holes, C, C, and plays under and up around the muffle D, standing on a fireclay slab. The doorway is closed by two fireclay blocks at E.
High temperature muffle-furnace, maximum temperature is 1,473 K (1,200 °C; 2,192 °F).