Heating mantles are used to heat flasks containing a sample. Heating mantles are used in place of Bunsen burners or hot plates when the sample is an organic liquid. Organic liquids have a tendency to burst into flames when exposed to direct heat, or release flammable organic vapors are heavier than air, which can explode when contacting open flames or heating coils. Mantles have an enclosed heating system, which is designed to avoid these dangers.
Fabric or Not
Heating mantles are available in either fabric or rigid constructions. Fabric mantles are flexible, and can be molded to accommodate a wide variety of flask shapes and sizes. The holding receptacles within rigid heating mantles are shaped either for a particular size flask, or simply have a large orifice that can be filled with sand to hold various size flasks. These sand baths serve to also provide a more uniform heating of the sample.
Why Fabric Heating Mantles Can be Dangerous
Fabric mantles are generally cheaper then rigid mantles, although they are susceptible to damage from spilled liquids. The covering fabric layered can be torn or frayed, by exposure to hot liquids or corrosives, exposing the wiring beneath. This can lead to a fire hazard.
How Heating Mantles Work and The Dangers of Wall Plugs
Heating mantles produce their heat by converting AC voltage. The intense energy draw needed to generate the high degree of required heat, can blow fuses or melt socket wiring. For this reason, heating mantles should never be plugged directly into a wall socket. Instead, a transformer, such as a variac, or some form of electronic relay or switch, should be used between the heating mantle and the wall socket.
Heating mantles are available in the following configurations: mantle and controller unit, mantle only, or controller only. Mantle and controller devices include both the mantle itself and the device used to controller it. This configuration may be either a single unit; a mantle with an integral controller, or it may be comprised of two separate parts, sold together. Mantle only devices are just the actual container for holding a flask; there is no temperature controller. Controller only devices are not mantles per se. They are simply the instrumentation board for controlling the heating of a mantle.