A heating mantle (also known as heating nest, heating basket or isomantle) is a laboratory equipment used as a heating source for various lab containers, as an alternative to other forms of heating bath. One of biggest advantage over other forms of heating devices is the ability to generate very high temperatures, with the piece of glassware being in direct contact with the heating mantle without increasing the risk of the glassware shattering, because the heating element of a heating mantle is insulated from the glassware to prevent excessive temperature gradients, usually with fiberglass.
There are many types of heating mantles. For the most common form, the heating element (electric wires) is embedded within a strip of fabric, generally fiberglass, forming a "nest" or "basket", where the container can be placed. The heating "nest" is encased in a cylindrical, truncated cone or sometimes hemispherical container, generally made of heat resistant plastic or aluminium or some other material. The current supplied to the device is regulated by a rheostat, generally attached on the outside of the container, which is used for achieving the desired temperature or temperature range.
Some heating mantles also have magnetic stirring function.
- Heating mantles can achieve higher temperatures than most heating devices
- Uniform heating of the flask
- Less tendency to generate harmful hotspots.
- Unlike oil or water baths, using a heating mantle generates no liquid residue to drip off the flask.
- Can only be used for round-bottom flasks
- Due to the fixed shape of the heating basket, only flasks of exact volume or very close volume can be used
Heating mantles can be found on eBay, Amazon, Aliexpress. Can also be bought from lab suppliers. Price varies depending on the brand, type and complexity.
DIY heating mantle
Heating mantles can be made by wrapping a heating tape in a hemispherical shape and placing it in a metal or ceramic container.
NurdRage made a good tutorial on heating mantles here. Should be noted however, that the heating element used doesn't last very long especially if used to generate very high temperatures and needs to be replaced more often.
- Heating mantles are very useful for distillations that require high temperatures, such as the distillation of sulfuric acid
- Reactions in round bottom flasks
Heating mantles can cause burns if touched without protection gloves. As they do not glow when hot, it is difficult to know how hot they are. A good tip is to hold a piece of glass over the basket, which will cause water vapor to condense on the glass if it's still hot.
After use, they must be let to cool on the table or in open air before being taken back in their storage closet.
Although heating mantles aren't illegal per see, in some places their purchase may be monitored. In US, the sale of all heating mantles with a volume of 22 liters (5.8 US gallons) are monitored. No mentions if heating mantles with a near volume are also included.