Your watch ran reliably for years and has been gaining several minutes a day for the past week? Before you think about an expensive service: in the vast majority of cases this is not a fault but magnetism. It is harmless, the cause is somewhere in your daily routine — and the fix takes less than a minute.
What magnetism does inside the movement
The rhythm of a mechanical watch is set by the balance wheel, restrained and returned by a hair-thin spiral spring. If that spring becomes magnetic, adjacent coils attract each other and in extreme cases stick together. The effective length of the spring shortens, the balance swings faster — and the watch runs fast. Not by a few seconds but often by minutes a day. No damage occurs: the movement is not broken, a magnetic field is simply trapped inside it.
The typical symptoms
- The watch suddenly runs sharply fast — the jump happens overnight, not gradually.
- The deviation is irregular and varies from day to day.
- There was no drop, no water contact, no repair beforehand.
- With strong magnetisation the watch may even stop and resume after a shake.
Everyday sources — mostly inconspicuous
- Magnetic closures on handbags, coats, tablet covers and laptop lids.
- Speakers, headphones and wireless charging pads — you put the watch beside them every night.
- Induction hobs, magnetic-handled tools, magnetic mounts in the car.
- Medical equipment: MRI and similar scans are the most drastic source of all. Take the watch off beforehand — which you should anyway.
- Magnetic clasps on bracelets and jewellery worn right next to the watch.
The compass test
All you need is a compass, or at a pinch a smartphone compass app on a steady surface. Move the watch slowly all the way around the needle, a few centimetres away. If the needle deflects and follows the watch, the movement is magnetised. If it stays still, the problem lies elsewhere — and a service or regulation really is due. The test costs nothing and answers the question in thirty seconds.
The fix: demagnetising
A demagnetiser generates an alternating field that decays slowly and dissolves the residual magnetisation in the movement. It takes seconds, the watch is not opened, and any watchmaker will do it for a small amount or as a courtesy. Afterwards the watch almost always returns immediately to its usual rate. Home remedies with strong magnets are a bad idea: a static field magnetises, it does not demagnetise.
How manufacturers fight back
The classic approach is a soft-iron inner case acting as a shield — familiar from post-war engineer and pilot watches. The modern approach is components that do not become magnetic in the first place: hairsprings in silicon or special alloys, plus antimagnetic pallet forks and escape wheels. The relevant standard for “antimagnetic” watches sets the threshold at 60 gauss; some modern movements quote a multiple of that. And a nice aside: the name of arguably the best-known antimagnetic model in watch history is simply “mille” plus “gauss” — a thousand gauss, the resistance rating turned into a model name.
Prevention beats measurement
- Do not rest the watch on speakers, charging pads or laptops overnight.
- Give it a fixed spot in wood or leather, at least a hand’s width from electronics.
- Always take it off before medical imaging and around magnetic tools.
- If the watch was regulated at a recent service and still runs fast: compass test first, then call the watchmaker.
Conclusion
A mechanical watch that gains minutes out of nowhere is hardly ever broken — it is magnetised. Compass test, a short trip to the watchmaker, problem solved. Knowing this can save you an unnecessary service.