In chemical and biological experiments, laboratory researchers and chemists frequently need to mix liquids and there are a variety of options at their disposal, including magnetic stirrers and overhead stirrers.
What is a magnetic stirrer?
Magnetic stirrers like the Velp Scientifica Multi-Stirrer utilize a rotating magnetic field to move a stir bar around in samples, thoroughly mixing the sample by rapid movement and agitation. Glass or other non-metal beakers prevent interference with the magnetic field. Applications include microbiology, biochemistry and micro titration stirrings.
What is an overhead stirrer?
Overhead stirrers are used in applications like chemical synthesis, pharmaceutical synthesis, physical and chemical analysis as well as in the petrochemical industry. They are motor-powered and immerse stirring tools into the beaker.
Which type of lab stirrer is best for me?
There are several points to consider when buying the best laboratory stirrer for your needs.
Volume & capacity
Typical magnetic stirrers are rated for volumes as high as 20 liters, while the top volume of overhead stirrers often range from 2 to 80 liters and up. Maximum volumes for both types of stirrers, unless otherwise specified, are based on water.
Consider viscosity: the magnetic stirrer’s bar has no direct connection to its motor, so fluid resistance may prevent mixing of higher viscosity samples.
Take desired speeds into account, as well. For very high or very low rpm settings, overheard stirrers boast a wider range (12 to 6,000 rpm). The low speeds for magnetic stirrers often start at 100 rpm. In some cases, the magnet could decouple at the magnetic stirrer’s highest speeds, leaving the stir bar bouncing around the edge of the beaker’s base instead of creating flow.
Advantages of overhead & magnetic stirrers
A magnetic stirrer reduces the chance of sample contamination: only the small stir bar comes in contact with the liquid. The stir bar’s size – ranging from a few millimeters to a few centimeters – makes it easier to sterilize.
An overhead stirrer’s tools are connected to the drive motor by a chuck, so it’s less likely to experience difficulty with a more viscous sample. The overhead stirrer also provides a variety of stirring tools, such as impellers, paddles and blades.
For mixing volumes in excess of two liters or for liquids with high viscosity such as emulsions, suspensions and oil mixtures, an overhead stirrer like the IP 54-rated Velp Scientifica OHS series might be appropriate.
Some magnetic stirrers – like the DLab MS-H280 or the Velp Scientifica AREX – incorporate a hotplate, allowing simultaneous heating and stirring of samples. It also offers the convenience of only needing one device that takes up little room on a bench.
Ultimately, with more power comes a higher cost. Magnetic stirrer best overhead stirrers in terms of price. But because each user’s needs will vary, there is no single “best” option for everyone. The decision to buy should be based on each user’s requirements.
Our recommended laboratory stirrers
A small and efficient magnetic stirrer for classrooms and labs with limited bench space.
A compact and economically priced LED display digital hotplate-stirrer ideal for temperatures below 280° C.
The OS40-Pro is capable of handling demanding laboratory task and offers constant speed even with changes in sample viscosity.
The OHS series offers state of the art stirring power combined with an easy to read digital display and integrated timer.