Stirology 101: Stir Bar Bounce
Why is my stirring bar bouncing around?
If your stir bar has a little too much pep in its step (i.e., it’s wobbling around on the bottom or bouncing along the edges of your vessel), then it’s lost its coupling with the magnetic field originating from the stirrer.
This can be caused by a variety of reasons. Some of the most common reasons include one or a combination of the following:
- The stirring bar is too weak. Try switching to a stronger stirring bar or even a rare earth stirring bar.
- The stirring bar size, type, shape is inappropriate for the application components. Try a different stirring bar. For example, if the length of the stirring bar magnet is longer than the length of the magnetic field, the stirring bar likely won’t work.
- The liquid is too viscous for the stirrer/stirring bar combination.
- The volume is too large for the stirrer/stirring bar combination.
- The bottom of the vessel is too convex and the stirring bar cannot find stability at the center of the stirring point.
- Your vessel is not directly on the center of the stirring point. Try repositioning your vessel.
- The rpm is set too high for the stirrer/stirring bar combination. Try decreasing the rpm or a soft reset (see below).
- In the case of electromagnetic stirrers, the power setting of the stirrer is too low—this means not enough power is going to the drive coils and the force of the magnetic field is too weak. Try increasing the power setting to make the magnetic field stronger.
- The stirring bar is too far from the stirring platform. Try reducing the vertical distance.
- Related to no. 9, the bottom of the vessel is too thick.
- Your vessel is too wide for the stirrer/stirring bar combination. Try a narrower vessel or a larger stirrer.
- A short interruption or reduction of power, causing the magnetic field to slow or become less intense.
- Remember it could be (and many times in fact is) a combination of the above.
- Or sometimes the stirring bar is simply thrown off based on a split second of the perfect storm of physics phenomena. Try a soft reset—i.e., press the power button off and back on. 2mag stirrers are equipped with SoftStart, so a soft reset will stop the stirring bar, recenter it, and slowly increase the rpm to the set speed to minimize/eliminate decoupling and stir bar bounce.
You can send us a video of your application and/or contact us to consult more on this issue. We can usually tell what the problem is and recommend solutions.