They are the most used in laboratories and at the same time the safest, because they use stirring bars that can be disinfected. This type of mixer is made up of a plate with a magnet or a series of electromagnetics, arranged in a circular shape at the bottom, which create a rotating magnetic field that acts by means of an electric motor controlled by an electronic device.
The (magnetic) stir bar, normally covered with an inert film such as Teflon, is placed inside the container and the beaker or container is placed on top of the plate. Once started, the stirring bar begins to rotate, propelled by the electric motor that moves the magnets. The size and shape of the magnetic bar determine the effectiveness of the stirring process, considering a constant speed. Some models of magnetic stirrers also have a heating system – some reach up to 300ºC – to heat the samples at the same time as they are stirred.