There are a variety of stirrers out there for lab, small business and home diy use, each having their own qualities which make them more suitable for certain applications and uses than others. Below is an outline of the different types of stirrers and their applications.
Magnetic stirrers use a rotating magnetic field to cause a stirrer bar, immersed within a liquid, to spin and therefore stir.
Most magnetic stirrers are suitable for small volumes of low viscosity. However there are some models which have been developed to handle large volumes and high viscosity.
There are magnetic stirrers that only stir aswell as magnetic stirrer hotplates that combine stirring functionality with a heating element which features can be used seperately or combined.
Analog vs Digital
Analog controlled magnetic stirrers control the speed and temperature settings with analog usually (knob) controls. This control setting is simple and easy to use, but will not be as precise in reaching specific stir speeds (rpm) and temperatures as digital.
Digitally controlled magnetic stirrers control the speed and temperature settings with a buttons or flywheels and display the metrics on a digital display. This allows for very accurate speed and temperature setting.
The plates of magnetic stirrers are generally made of either ceramic or stainless steel.
Ceramic top plates have excellent chemical resistance, so they are ideal if you are working with corrosive chemicals which may splash onto the plate surface. The white surface also means they are good for titrations or other work where clear visibility of colour is essential.
Ceramic top hotplates can withstand high temperatures of up to 450 degrees celcius. They are also easy to wipe clean.
CAUTION: only heat glassware with Ceramic hotplates, not metal containers. Ceramic hotplates are also not suitable for sand baths and any vessel which will reflect heat back onto the surface which can cause cracking.
A stainless steel top plate does not produce eddy currents like aluminum does and therefore ensures a very powerful coupling and stirring action. Stainless steel hotplates CAN be used to heat metal containers.
Aluminum Top Hotplates
Aluminum top plates are thicker and more robust than ceramic plates and therefore can withstand knocks and rougher use. Aluminum hotplates offer consistent temperature over the plate and heat up to the edges of the surface plate. Aluminum hotplates CAN also be used to heat metal containers.