What is a Muffle Furnace? - Laboratory, Box, Tube, Muffle . 2015725What is a Muffle Furnace? July 25, 2015 Jon Guibor CM Furnaces, Muffle Furnace High Temperature Furnace, Retort Furnace Jon Guibor While the term " Muffle Furnace " or " Retort Furnace " is still in use today, it doesn't really mean the same thing as it did in the early 20 th century when wood and coal were the primary ways to heat