Magnetic Stirrers Frequently Asked Questions
What is the best laboratory magnetic stirrer?
Selecting the perfect magnetic stirrer for your applications from the thousands of models available can be overwhelming. To ensure optimal stirring of your solutions, it is important to find a magnetic stirrer that is suitable not only for the types of samples you are working with, but also for all your application needs. Consider the pros and cons of each and think about what additional features you may need in the future. Get the best-fit magnetic stirrer for your lab protocols with our interactive selection guide.
Can magnetic stirrers be operated over a longer period or is there a maximum duty cycle?
Magnetic stirrers can be operated 24 hours a day for several days. There is no maximum duty cycle specified.
Is there a maximum weight with which a magnetic stirrer may be loaded?
Yes, magnetic stirrers can carry the maximum volume of water plus the weight of a common vessel.
At what speed should you set the magnetic stirrer?
The optimal speed depends on several factors, e.g. on the application and your sample. It is important to ensure a uniform mixing. Therefore the speed should not be too low. The most common applications require speeds between 400 and 800 rpm.
Can magnetic stirrers process liquids with high viscosity?
No, a magnetic stirrer is made to work with aqueous solutions or low viscosity media up to 100 mPa. Solutions with high viscosity or high density are barely mixed using this method. Overhead stirrers are usually required to handle higher viscosities.
Under which environmental conditions should a magnetic stirrer be operated?
The ambient temperature should be permanently between +5°C and +40°C with relative humidity not exceeding 80%. There are some speciality stirrers that can operate under special conditions. They that can be submerged in water baths and used in CO2 incubators. Filter for speciality application in our slection tool to find them.
What is magnetic stirrer with hot plate used for?
The hotplate stirrer (or hot plate stirrer or hot plate magnetic stirrer) is used for mixing and heating aqueous solutions for a great variety of chemical, biological and microbiological applications.
What is the difference between a ceramic top plate and a stainless-steel top plate?
Ceramic plates have excellent chemical resistance and are therefore ideal if you work with corrosive chemicals that could splash onto the plate surface. They can withstand higher temperatures of up to 450°C and are easy to wipe clean. The white surface of a ceramic top plate is well suited for titrations or other work where clear visibility of the colour is required.
A stainless-steel top plate does not generate eddy currents (like aluminium) and therefore ensures very strong coupling and agitation. Aluminium top plates are more robust and resist accidental impacts better than ceramic plates.
How can magnetic stir bars be sterilised?
Most stir bars (also known as magnetic fleas) are coated with PTFE and can be sterilised by autoclaving or treating with alcohol or mucocite.
How do I choose a magnetic stir bar?
Choosing the right size and shape of magnetic stir bar ensures efficient mixing and reduces wear and tear on the PTFE coating. The length should be equal to 2/3 of the diameter of the vessel bottom. The power of the bar is dependent on the diameter of the magnet. Regarding the shape, we have the following recommendations based on the vessel:
- Straight bars for flat-bottomed vessels
- Bars with a central ring for slightly convex-bottomed vessels
- Oval bars for balloon-shaped vessels
- Triangular bars for dissolving solids and sediments (where the flat surface of the bar can scrape the bottom of the vessel).
What are the different types of magnetic stirrer to consider?
- Analog stirrers
Analog stirrers feature electronic speed control for constant speed even with changes in sample load and usually have low thermal stability. - Digital stirrers
Units either have LCD or LED displays that show rotation speed and temperature, allowing easy adjustment until the appropriate target values are reached to ensure speed and heat control and maintenance. - Multi-position stirrers
This type can stir multiple beakers or flasks on the platform at the same time. - Cell culture stirrers
Cell culture stirrers are designed for care and protection of thermally sensitive cultures such as microcarrier cultures, culture broths and cell suspensions. They provide gentle agitation and low heat dissipation to protect sensitive cell cultures within CO2 incubators.