Magnetic stirrers are a crucial component of a science experiment. Yet, over-relying on their indicators can be dangerous. The issues brought by misleading indicators from your stirrers can compromise the whole study.
Let’s take a look at the vital moments when your indicators may “lie” and how you can improve research accuracy. To begin with, consider using laboratory overhead stirrers to improve the lab performance.
The Hidden Problem Behind “Perfect” Stirring
Sometimes, the stirring may appear to be “perfect”, but there are actually unseen issues playing in the background.
Mixing quality
Even if the stirrers appear smooth and quiet, it doesn’t indicate good stirring quality. Stirrers only measure the motion, not mixing quality. Researchers should always verify and examine the mixing results, instead of overrelying on stirrers alone.
Energy transfer
The stronger the viscosity, the weaker the magnetic coupling. The motor may be spinning at the set speed, but the stir bar is hardly rotating. The energy transfer inefficiency creates common misleading stirrer indicators that confuse researchers.
Misleading Visual Cues Researchers Often Trust
What you see isn’t always true, especially in lab settings.
The vortex trap
Many scientists fall for the vortex trap, mistakenly believing that a deep vortex ensures good mixing. In reality, it may only indicate surface mixing. It can cause trouble for bulk circulation.
Coloured solutions
Oftentimes, workers rely on sound or RPM when they can’t see through the coloured solutions. Not checking the solutions carefully will likely lead to misinterpretation.
Liquid motion
A smooth liquid motion does not necessarily mean the mixing is perfect. You should not rely on the visuals alone to draw conclusions.
When the Magnetic Bar Is the Real Culprit
When working with a magnetic stirrer, you need to understand its properties and capabilities.
Incorrect sizing
A bar that is too small will never mix evenly. On the other hand, a bar that is too big will cause damage to the walls and spin erratically.
Demagnetization
Over time, demagnetization will happen due to prolonged exposure to high heat. It will lead to the stir bar losing efficiency, lacking the torque to move.
Decoupling
Incorrect matching will lead to decoupling. The stir bar could spin out. When that happens, you may still see high RPM on the reader, but the stirrer is simply rattling at the bottom.
Temperature Indicators That Misrepresent Mixing Efficiency
Misleading stirrer indicators can appear to “falsify” temperature and mixing efficiency.
Uneven temperature
Problematic stirring will lead to drastically uneven temperatures between the top of the flask and the bottom of the flask. A single temperature read will not reflect the actual conditions.
Temperature probe placement
An external temperature probe too close to the stir bar will cause incorrect readings. This is due to the turbulence and uneven heat distribution.
Load Indicators That Trick You Into Thinking Everything Is Fine
Here are the main causes for load indicator problems you should avoid.
Low load reading
A low load reading is usually seen as “perfect”, when it could simply mean that the bar is slipping. You should not trust the load indicators completely without further examination.
High load reading
In contrast, a high load reading doesn’t always mean something is wrong. It could just be that there is an increased viscosity.
How to Properly Read Your Stirrer: A Practical Checklist
Follow these tips to prevent yourself from being misled by indicators.
Observe indicators
Observe different indicators, such as sound consistency, surface motion, and temperature stability, simultaneously. Identify contradictory or unusual readings.
Stop stirring if necessary
If something doesn’t feel right, stop the stirring process immediately. You do not have to wait until the end to check for issues.
Increase speed gradually
Increasing the speed gradually can usually allow you to spot bar decoupling and dead zones more easily and accurately.
Tools and Upgrades That Reduce Misleading Readings
Working with high-quality tools can minimize deviations from equipment faults. Get the best lab upgrades from IKA to guarantee quality and performance.
Overhead stirrers
Overhead stirrers are a more reliable upgrade. They work better with high viscosity and are mechanically stronger. They do not get decoupled during the process.
Proper training
Regardless of what stirrers you choose, make sure to always provide proper and adequate training to lab staff. They need to know about different safety features and indicators to keep a seamless workflow.
In Conclusion
There are times when your magnetic stirrers do not seem to be reliable. The indicators alone are not a great source for verification.
You should always cross-examine the readings and results. Set a detailed protocol for the facility to increase staff awareness as well.
