Demagnetisation of a mechanical watch

How to demagnetise a mechanical watch yourself

Author: Edgar Colomb, Liestal, Switzerland

Online since: 02/10/2014, Number of visits: 162094

The problem

When I was handling your magnets, I inadvertently magnetised my mechanical watch. As a result, it was five minutes fast every day – simply unacceptable. It is most likely, that the balance wheel spring was magnetised by mistake.

But whenever super magnets cause a problem, they can also solve them. Here is my suggestion for a low-cost watch demagnetisation, which I successfully tested on my own expensive watch. I am a physicist, but the instructions were written in laymen’s terms.

non-magnetic material

What does "magnetised" mean?

The atomic molecular magnets in non-magnetic materials are omnidirectional. Their effect is cancelled out.

magnetised material

In magnetised iron/steel (most of) the molecular magnets are aligned in one direction and the effect is cumulative.

Iron/steel can be magnetised by using super magnets, for example.

Methods of demagnetisation

In general, there are 3 options for demagnetisation:

Apply heat above the "Curie temperature" (768 °C for iron). Molecular magnets will lose their orientation if the thermal motion is sufficiently strong. Quite obviously, this is not the correct method for expensive watches.
Extreme jolts and blows. Expensive watches don't like those either.
An external, in strength decreasing, alternating magnetic field will disable the orientation of the molecular magnets. This is the correct method, not just for watches!

Practical application

Glue a neodymium rod magnet (for example S-06-25-N) or several small disc magnets (Caution, don’t use magnets that are too strong!) to the head of a thick nail and insert the nail into the chuck of a drill or cordless screwdriver. Then, with the watch a few millimetres away, start operating the drill at low speed. Now very slowly move the drill away from the watch to a distance of about 10 cm. The result in my case: The watch is again keeping accurate time!

I had this idea because the local watchmaker wanted to charge an unrealistic price for a demagnetisation with special equipment and estimated that this procedure of a few seconds would take one week.

What works for watches can also be applied to other objects.

A note from the supermagnete team:

What worked for the watch of Mr Colomb may not necessarily work for all other inadvertently magnetised objects. For valuable items, we recommend that you consult an expert (i.e. a watchmaker). We, here at supermagnete, cannot offer any guarantee whatsoever that the method used by Mr Colomb is going to work for other objects – improper handling or the use of magnets that are too strong may make the problem even worse.