How to Demagnetise a Watch: Signs, Causes, and Fixes
Signs of Magnetism
Magnetism is the most common cause of sudden accuracy changes in mechanical watches. A magnetised watch may run minutes fast or slow per day, and the deviation often changes with position.
Common signs:
- Sudden large rate change after no obvious mechanical event
- Watch running very fast (often tens of seconds to minutes per day)
- Inconsistent rate between positions
Common Sources
- Laptop lids and speakers
- Magnetic phone cases and clasps
- Tablet covers with magnetic closures
- Hi-fi speakers and headphones
- Magnetic bag closures
- Some furniture and cabinet latches
Modern phones are less magnetically strong than older devices, but magnetic cases and accessories remain a common cause.
How to Demagnetise
A demagnetiser is an inexpensive device that generates an alternating field to neutralise the watch's residual magnetism.
- Place the watch on the demagnetiser surface
- Press the button to activate the field
- Withdraw the watch slowly while the field is active
- Release the button once the watch is clear
- Check the rate over 24 hours
Withdrawing slowly is important. Removing the watch quickly can leave residual magnetism.
Do It Yourself or Professional
Demagnetising is safe and simple. A basic demagnetiser costs very little and is worth owning if you have mechanical watches. Watchmakers will also do it quickly and cheaply.
If demagnetising does not resolve the rate issue, the cause is likely mechanical and a service is indicated.
Prevention
- Keep watches away from speakers and magnetic closures
- Do not rest a watch on a laptop or tablet cover
- Check magnetic clasps on bags and phone cases
- Consider anti-magnetic movements if you work around magnetic fields
Anti-Magnetic Watches
Anti-magnetic watches use non-magnetic materials, particularly silicon for the hairspring and escapement, or a soft iron inner cage to shield the movement.
- Silicon components: inherently non-magnetic, used in modern movements
- Soft iron cage: traditional shielding, adds thickness
- Ratings: some watches are rated to withstand substantial magnetic fields
For most wearers, prevention and occasional demagnetising are sufficient. Anti-magnetic construction matters if you work with strong magnets or medical equipment.
FAQ
How do I know if my watch is magnetised?
A sudden large rate change, often running very fast, is the typical sign. Demagnetising is a safe first test.
Can demagnetising damage a watch?
No, when done correctly with a proper demagnetiser. It is a routine procedure.
Will a smartphone magnetise my watch?
Phones themselves are usually not strong enough, but magnetic cases, mounts, and accessories can be.