How to Build a Magnetic Stirrer

Written by katharynb
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How to Build a Magnetic Stirrer
Magnet (Schwebender Magnet image by Edwar Xie from

Magnetic stirrers are used in laboratories and in everyday situations to continuously stir solutions. A magnetic stirrer allows a person to go about his or her activities while the stirrer is busy combining elements. Stirrers are typically used to blend a solid chemical with a liquid chemical to create a solution.

Skill level:

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Things you need

  • Working computer fan 12V dc
  • Working power supply 12V dc
  • Computer hard drive
  • Nail polish remover
  • Canning jar lid
  • Electrical tape
  • Super glue
  • Scrap wood block 5cm wider than the computer fan
  • Piece of Plexiglas 5cm wider than the computer fan
  • Wood screws
  • Drill or screw driver

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  1. 1

    Attach computer fan to the widest side of the block of wood using wood screws that fit the mounting bracket of fan.

    How to Build a Magnetic Stirrer
    Computer Fan (computer cooler image by Soja Andrzej from
  2. 2

    Making sure that all electrical components are unplugged, connect the wires of the computer fan to the power supply. Splice together hot-to-hot wires and ground-to-ground wires. Wrap spliced wires using electrical tape. Plug in the power cord to make sure fan works. You can add a dimmer switch to control speed or an on/off switch. Glue canning jar lid to top of fan.

    How to Build a Magnetic Stirrer
    Rare Earth Magnet (Power Pack image by Cinneman from
  3. 3

    Remove rare earth magnet from hard drive. Some magnets are held in place by both magnetism and a thin layer of glue. A bit of nail polish remover will dissolve the glue and make removal easier.

    How to Build a Magnetic Stirrer
    Centring Magnet (Hard Drive image by Tabitha Little from
  4. 4

    Place magnet in centre of the lid and plug in power cord to power supply to test to see if the magnet is centred. Adjust the magnet's position until you experience no wobble or vibration. Even a slight wobble can increase over time and disrupt the stirring process. Although the magnet should stay in place, it is a good idea to glue the magnet to the lid once the proper place has been located.

    How to Build a Magnetic Stirrer
    Centring (arrow and target, focus in arrow image by T.Tulic from
  5. 5

    Mount the Plexiglas between 2.5 and 4mm above the magnet using any type of spacer. Place magnetic stir bar on Plexiglas, turn on the fan and watch it spin.

Tips and warnings

  • Any cylindrical magnetic piece of metal will work as a magnetic stir bar. Research the reactivity of the specific magnetic metal with whatever you will be stirring.
  • Rare earth magnets are a choking hazard for small children. If swallowed, immediate medical attention is advised.
  • Always use caution when dealing with electricity.
  • Rare earth magnets should be kept away from electronic equipment, computer discs and credit cards.

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