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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 thorugh 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.
A muffle furnace is (usually) 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. They are also used in many research facilities, for example by chemists in order to bake the moisture out of a sample to ensure it is completely dry.
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 heating elements. Therefore there is (usually) no combustion involved in the temperature control of the system, which allows for much greater control of temperature uniformity.
