Magnetic Stirrer

As a customer, you can always contact the sales and technical support team at PCE Instruments (PCE) for assistance in obtaining the best product for your specific task. In addition, to aid in your purchasing process, the team at PCE has put together the following notes to consider when buying a magnetic stirrer.

What magnetic stirrer design features are best suited to your needs?
PCE's magnetic stirrer products come with different design features. To determine which magnetic stirrer design features will best meet your needs, start by identifying the anticipated sample volume and container size/shape. The maximum stir volume and size of the stir plate should more than accommodate the specifications of the sample and container. PCE offers magnetic stirrers with rectangular or round stir plates for stir volumes of 400 ml / 0.1 gallon, 800 ml / 0.2 gallon or 2 L / 0.5 gallon water samples. PCE's stir plates also accommodate Ø 94 mm / 3.7" or Ø 145 mm / 5.7" containers or beakers. To avoid overloading your magnetic stirrer, we recommend selecting a magnetic stirrer model capable of handling sample volumes and beakers slightly larger than what is required.

Other key design features include the number of stir points, the ingress protection rating and the footprint of the magnetic stirrer. A multi-position magnetic stirrer is ideal for conducting series of tests under reproducible conditions. Protection against the ingress of liquids is essential to allow for cleaning of the magnetic stirrer and to prevent accidental spills from ruining the magnetic stirrer's electronic components. A compact, low-profile or flat magnetic stirrer can save valuable counter space in an otherwise crowded laboratory. In addition, magnetic stirrers with inductive stirring drives are extremely quiet, keeping the noise footprint to a minimum.

What stirring speeds are required?
PCE's magnetic stirrers have variably adjustable stirring speeds. Some PCE magnetic stirrers boast maximum stirring speeds of up to 1250 and 1500 revolutions per minute (rpm). Since the stirring force is magnetic, magnetic stirrers operate virtually friction-free and can be run continuously at high speeds for several hours at a time. However, please note that you should never turn on a magnetic stirrer at full stirring speed. Starting a magnetic stirrer at full speed can throw the stir bar off balance and into the side of the mixing container, causing glass beakers to shatter and break. Instead, the magnetic stirrer should be turned on at a low speed, and then slowly the speed can be increased up to the full level. Some PCE magnetic stirrers have built-in soft-start functionality, i.e., the magnetic stirrers automatically start by stirring slowly, and then gradually pick up speed.

The viscosity of the sample also affects start-up stirring speed selection. In viscous liquids, extremely high stirring speeds can keep the stir bar from following the magnetic field. Therefore, when stirring high-viscosity liquids, you should start your mixing process using a low rpm, and then slowly increase the stirring speed up to the desired rpm.

Another useful stirring function is reverse stirring. Reverse stirring allows for a change in the direction of the stirring rotation. Stirring your samples in two directions can help achieve maximum homogeneity and solubility. 

What kinds of liquids will you be stirring?
PCE's magnetic stirrers are ideal for mixing a wide variety of liquids in open and closed containers. Thus, it is possible to work with liquids or chemicals that must be sealed off from the surrounding environment for safety reasons. The use of chemically inert stirring bars and containers makes it possible to mix almost any liquid to a certain degree of viscosity. For fluids with very high viscosities, a magnetic stirrer with a shaft is recommended as the shaft can transmit higher forces. In addition, some magnetic stirrer models can heat liquid samples to lower viscosities to enable mixing.

Which magnetic stirrer accessories are necessary?
There are a variety of accessories available for magnetic stirrers including but not limited to magnetic stir bars, magnetic bar removers, round-bottom beakers and temperature probes.

 - Magnetic stir bars or stir sticks typically are included in the delivery contents of the magnetic stirrer, but additional or replacement stir sticks may be desired. Magnetic stir sticks should feature chemically inert coatings, as the sticks serve to mix the liquid samples from within. Each magnetic stirrer should state in the user manual or technical specifications the recommended stir stick size and shape.

 - Magnetic bar removers usually are optional accessories. Magnetic bar removers are commonly 20 to 30 cm / 7.9 to 11.8" in length and also feature chemically inert coatings. Magnetic bar removers quite simply are used to remove magnetic stir bar and stir sticks from the liquid samples.

 - Round-bottomed beakers or flasks are optional spherical glass containers or vessels typically used for chemical or biochemical work.

 - Temperature probes, such as PT-1000 sensors, are optional and can be attached to magnetic stirrers for more accurate temperature control. When using a magnetic stirrer without a temperature probe, bear in mind the practical rule that in the majority of cases the temperature of the hot plate must be twice the desired internal temperature of the liquid sample.

Should you need help choosing the right magnetic stirrer and accessories, the friendly and knowledgeable staff at PCE is here to help. Please contact us at or +44 (0) 2380 987 035 for PCE Instruments UK, or at or +1 (561) 320-9162 for PCE Americas Inc.

A magnetic stirrer uses a rotating magnetic field to manipulate a magnetic stir bar or stir stick (also called a flea) immersed in a liquid for the purpose of mixing. Magnetic mixing technologies often are preferred to mechanical mixing technologies, as magnetic mixers are much quieter, more efficient and require little to no maintenance. Most magnetic stirrers require the use of glass vessels or other containers made of materials not affected by magnetic fields. Since the magnetic stir bars are small in size, they are easy to clean and disinfect, if necessary. Magnetic stirrers are used predominately in chemical, microbiological, biomedical and pharmaceutical laboratories, because magnetic stirring can be used to mix liquids in hermetically sealed containers. A magnetic stirrer is also an essential piece of equipment in industrial research and product development laboratories. Magnetic stirrers can be used to mix everything from low-viscosity industrial adhesives and coatings to paints and solvents.

When mixing sensitive samples, such as cell and tissue cultures, a heatless magnetic stirrer with slow mixing speeds is recommended. Thus, magnetic stirrers without heat are suitable for use in incubators and cold rooms, as the technology ensures negligible heat transfer from the magnetic drive to the culture vessel. Heatless magnetic stirrers also can be used for overnight stirring, providing proper safety precautions are in place. On the other hand, when mixing more viscous liquids, a magnetic stirrer with a hot plate can come in handy, as heat can thin the sample to allow stirring. However, a heated magnetic stirrer or hot plate should never be used for overnight stirring, because the fire risk is too great.