Magnetic Stir Bars

A magnetic stir bar is a small magnet designed to rotate inside a container of liquid when driven by the rotating magnetic field of a magnetic stirrer. This allows liquids to be mixed without a mechanical stirring shaft passing through the container.

Magnetic stir bars are used for mixing liquids in chemistry, laboratory research, science projects, brewing, pharmaceuticals, biotechnology other applications where controlled stirring or continuous mixing is needed.

PTFE stands for polytetrafluoroethylene, a material commonly associated with the Teflon™ brand name. PTFE is chemically resistant and relatively nonreactive, making it well suited for coating magnetic stir bars used with many laboratory liquids and chemicals.

A magnetic stirrer creates a rotating magnetic field beneath the container. The magnetic stir bar inside the liquid follows this rotating field, causing the bar to spin and circulate the liquid around it.

Stirring performance can often be improved by increasing the strength of the driving magnet or changing the magnet configuration to provide greater torque to the stir bar. Container thickness, distance between the magnets, stir bar size, liquid viscosity and stirring speed can also affect performance. Learn more in our Magnetic Stir Bars article.

Neodymium magnets provide strong magnetic fields in a compact size. This makes them useful for magnetic stir bars where the internal magnet must respond effectively to the driving magnetic field while remaining small enough to rotate inside the container.