History and What It Became

The muffle furnace's shielded-chamber principle is documented in the major sixteenth-century metallurgical manuals, Georgius Agricola's De Re Metallica of 1556 and Vannoccio Biringuccio's De la Pirotechnia of 1540, both of which describe assaying and refining furnaces built to keep fuel and charge apart. Cupellation is the process this furnace type is most tightly bound to: separating precious metal from base metal by oxidizing the base metal away in a small porous cupel required exactly the clean, even, contamination-free heat only a shielded muffle chamber could reliably deliver, and Agricola describes the technique in enough detail that modern metallurgists can compare it directly to present-day fire assaying.

The design proved remarkably stable across four centuries of change: unlike most of the apparatus in this category, the muffle furnace crossed from wood and charcoal fuel to gas and eventually electricity without needing any change to its basic layout of an enclosed inner chamber heated from outside. A muffle furnace, now almost always electric, remains standard equipment today in chemistry and materials science laboratories, in dental and ceramics work, and in fire assay offices that still use cupellation, under the same name it carried in the sixteenth century.