Magnetisation of mechanical watches

Magnetism can affect timekeeping

A mechanical watch may become magnetised through exposure to a magnetic field. It can then gain or lose time. The effect may persist after the watch is moved away from the source, unlike a purely temporary disturbance while it is beside a magnet.

Practical signs and limitations

Speakers and magnetic handbag clasps are examples of sources owners should consider. Changed timekeeping alone is not a diagnosis, however. Ask a watchmaker to examine the watch and assess demagnetisation. This treatment must be distinguished from a full service or a promise to resolve unrelated faults.

Do not transfer specifications between watches

Magnetic resistance depends on the particular construction. A specification for a new model does not establish equivalent protection in an older watch from the same brand. Analogue quartz and mechanical watches may also respond differently. Establish the model and movement before applying the manufacturer's advice.

Documentation and next steps

Practical example: Record when the timekeeping changed and whether the watch was beside a speaker. Keep service papers with its ownership history. Browse pre-owned wristwatches, or send OBA photographs when considering a sale. Disclose known timekeeping deviations and any examinations.