Hotplate Stirrers: How to Choose Between Ceramic, Aluminium and Coated Top
- Jul 30
- 7 min read
Quick Summary
A hotplate stirrer without a temperature probe controls the plate, not your liquid. The plate surface can sit far above the temperature of the medium, which is why reactions overheat, solvents flash off and results drift. A contact thermometer moves control into the flask and is the most worthwhile accessory in this category.
Plate material decides chemical resistance and heat-up speed, and the two trade against each other. Aluminium heats fast, ceramic resists chemicals, coated aluminium is the usual compromise.
Prices run from £83.22 for a basic magnetic stirrer to £1,526.65 for a fully specified heating and stirring package.
What is a hotplate stirrer?
A hotplate stirrer is a benchtop instrument that heats a vessel from below while a rotating magnet spins a stir bar inside it, giving simultaneous heating and mixing without anything entering the liquid.
That last point is why the design has survived unchanged for decades. The only thing in contact with your chemistry is a PTFE-coated stir bar, so there is no shaft, no seal and no contamination path.
Three things vary between models: the plate material, the temperature control method, and the safety features. Everything else is packaging.
Which plate material should I choose?
Aluminium for speed, glass ceramic for aggressive chemicals, coated aluminium for almost everything else.
Plate material | Heat-up speed | Chemical resistance | Best for |
Aluminium alloy | Fastest | Moderate. Attacked by strong acids and alkalis | General heating where spills are unlikely |
Anodised aluminium | Fast | Better than bare aluminium | The standard upgrade, and why several models list an “Anodized” variant |
Ceramic-coated aluminium | Fast | Good | The usual compromise, and the most common plate in current ranges |
Glass ceramic | Slower | Excellent, including acids | Aggressive chemistry, and where spills are routine |
Stainless steel | Fast | Good, but not to chlorides | Robust general-purpose use |
The practical rule: if you spill on the plate regularly, buy for chemical resistance. If you are heating water and buffers all day, buy for speed. A pitted, corroded plate heats unevenly long before it stops working, so resistance is a longevity decision as much as a safety one.
Note that several models in the IKA range are offered in both standard and Anodized versions at the same nominal specification. That choice is exactly this trade-off.
Why does a contact thermometer matter so much?
Because without one, the instrument controls the temperature of the plate, and you care about the temperature of the liquid.
Set a plate to 100 °C with a beaker of water on it and the water will settle well below that, because heat is lost through the glass and from the surface. Set a plate to 150 °C to make a viscous mixture reach 100 °C and the glass in contact with the plate may be far hotter than the bulk liquid. Local overheating degrades product, and with a flammable solvent it is a genuine hazard.
A contact thermometer is a PT1000 probe that sits in the medium and closes the control loop where it matters. The instrument then holds your liquid at setpoint and modulates the plate to achieve it. Typical accuracy in the medium is within a degree, against a plate-control error that can run to tens of degrees.
Options in our range:
ETS-D7 wireless sensor, £437.00
PT Wireless probe, £173.85
Several IKA models are sold as bundled “Solutions” with the probe already included, which is usually cheaper than buying the two separately and removes the compatibility question.
How do I choose a stir bar?
Length roughly two-thirds of the vessel’s base diameter, and match the shape to the vessel.
Too short and coupling is weak, so the bar decouples and rattles at speed
Too long and it fouls the vessel wall
Plain cylindrical bars suit flat-bottomed beakers and flasks
Octagonal bars with a pivot ring run more smoothly on flat bottoms
Egg or football shaped bars suit round-bottom flasks
Cross or triangular bars help in vessels with an uneven base
Decoupling, where the bar stops following the magnet and starts jumping, has three usual causes: the bar is too small for the volume, the speed was raised too abruptly, or the mixture is too viscous for magnetic stirring at all. Ramp the speed up rather than starting at maximum.
When magnetic stirring stops working. Magnetic coupling is limited by viscosity and volume. Above roughly 20 litres of water-like liquid, or with anything genuinely viscous such as polymers, gels or slurries, no stir bar will do the job. That is the point at which you need an overhead stirrer, which drives an impeller on a shaft and does not rely on magnetic coupling at all.
What safety features should I look for?
A settable temperature limit is the one that matters. It caps the maximum plate temperature independently of the setpoint, so a mis-set dial or a controller fault cannot take the plate to full power. Set it below the flash point of the solvents you use.
Also worth confirming:
Hot plate warning. An indicator that stays lit while the plate is above roughly 50 °C, after the instrument is switched off
Error detection. The unit should cut heating if the probe is disconnected or fails
Spill containment. A sealed housing with no vents on the top surface, so a spill runs off rather than into the electronics
Stable footprint and a stand. A tall support rod with a heavy vessel on a small hotplate is an accident waiting to happen
Where flammable solvents are involved, hotplate stirrers fall within the scope of DSEAR and the substances themselves under COSHH. Setting the temperature limit below the solvent flash point is a control measure, and worth recording as one.
Hotplate stirrer or heating mantle?
Use a hotplate stirrer for flat-bottomed vessels and a heating mantle for round-bottomed flasks.
A round-bottom flask touches a flat plate at a single point, so heat transfer is poor and that contact point overheats. A heating mantle wraps the flask and heats the whole curved surface evenly. If you are running reflux in a round-bottom flask, a mantle is the correct tool. If you are dissolving, buffering, titrating or preparing media in beakers and conical flasks, a hotplate stirrer is right.
Hotplate stirrers from LS Scientific
We stock IKA, VELP and Hanna across the range. Prices verified 29 July 2026 and include current reductions. Several IKA units are on introductory offer, so check the live price before quoting.
IKA, complete solutions with probe included
Model | Was | Price |
£1,607.00 | £1,526.65 | |
£1,542.00 | £1,464.90 | |
£1,348.00 | £1,078.40 (introductory offer) | |
£1,108.00 | £1,052.60 |
IKA, instruments
Model | Was | Price |
£948.00 | £900.60 |
Both RCT and RET are available in standard and Anodized plate versions. RET sits above RCT on temperature control and display, which is the specification to compare if your process has a tight temperature tolerance.
VELP
Model | Was | Price |
£1,172.47 | £1,113.85 | |
£1,096.55 | £1,041.72 | |
£974.55 | £925.82 | |
£928.36 | £881.94 | |
£879.35 | £835.38 | |
£831.29 | £789.73 |
A protective cover for the AREX 5 Advance is £24.80, and worth having wherever spills are likely.
Entry level, stirring only
Model | Was | Price |
£87.60 | £83.22 | |
£87.60 | £83.22 |
These stir but do not heat. Appropriate for dissolution, titration and sample preparation at ambient temperature.
Related: overhead stirrers for viscous or large-volume work, water baths for gentle uniform heating, glassware and dry block heaters.
Tell us your vessel size, your solvent and your temperature tolerance and we will tell you which model and which probe. Talk to our technical team.
Frequently asked questions
What is a hotplate stirrer used for? Heating and mixing liquids at the same time in a laboratory. Common uses are dissolving solids, preparing buffers and media, running reactions, and holding a sample at temperature during titration.
What is the difference between a hotplate stirrer and a magnetic stirrer? A magnetic stirrer only mixes. A hotplate stirrer mixes and heats. If you never need heat, a stirrer-only unit costs a fraction of the price.
Which plate material is best? Coated or anodised aluminium suits most laboratories, balancing fast heat-up with reasonable chemical resistance. Choose glass ceramic if you work with aggressive chemicals or spill frequently. Choose bare aluminium only where speed matters and spills are unlikely.
Do I need a contact thermometer? If the temperature of your liquid matters, yes. Without a probe the instrument controls plate temperature, which can differ from the medium by tens of degrees. With a probe it controls the medium directly, typically within a degree.
What size stir bar should I use? Roughly two-thirds of the vessel’s base diameter. Use octagonal bars in flat-bottomed vessels and egg-shaped bars in round-bottomed flasks.
Why does my stir bar keep jumping out of sync? Decoupling, usually because the bar is too small for the volume, the speed was increased too abruptly, or the mixture is too viscous for magnetic stirring. Ramp the speed gradually, and move to an overhead stirrer if the liquid is genuinely viscous.
When should I use an overhead stirrer instead? Above roughly 20 litres of water-like liquid, or with any viscous medium such as gels, polymers or slurries, where magnetic coupling can no longer transmit enough torque.
Can I use a hotplate stirrer with a round-bottom flask? It is not ideal. A round-bottom flask contacts a flat plate at one point, so heating is uneven and that point overheats. Use a heating mantle for round-bottom flasks.
How much does a hotplate stirrer cost in the UK? From £83.22 for a stirrer without heating, around £900 for a heated laboratory model, and up to £1,526.65 for a fully specified package with a contact thermometer included.
References and standards
The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR), Health and Safety Executive. Applies wherever flammable solvents are heated.
Control of Substances Hazardous to Health (COSHH), Health and Safety Executive.
BS EN IEC 61010-2-051:2021+A11:2021, Safety requirements for electrical equipment for measurement, control and laboratory use: particular requirements for laboratory equipment for mixing and stirring. The current electrical safety standard for this equipment class.
BS EN IEC 61010-2-010, particular requirements for laboratory equipment for the heating of materials.
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