A magnetized automatic runs fast. Sometimes 30 seconds a day fast. Sometimes it stops entirely. The culprit is almost always something mundane: a speaker, a laptop, a magnetic closure on a handbag. Modern life is full of magnetic fields, and watches pick them up whether you notice or not. This guide covers how magnetism affects watches, where it comes from, and how to protect against it.
How Magnetism Damages a Movement
A mechanical movement contains dozens of small steel parts: the hairspring, balance wheel, escape wheel, gear train components. Steel parts exposed to a magnetic field retain some magnetism. Magnetized parts attract each other, creating friction and timing errors.
The hairspring is most susceptible. A magnetized hairspring coils tighter, which speeds the balance wheel, which speeds the watch. Severe magnetism can stop a watch entirely.
Where Magnetism Comes From in Modern Homes
| Source | Field Strength | Typical Distance Matters |
|---|---|---|
| Refrigerator magnet | 10 to 100 gauss | Direct contact only |
| Speaker (large) | 20 to 200 gauss | Within 6 inches |
| Laptop / tablet magnetic closures | 50 to 100 gauss | Within 2 inches |
| Induction cooktop | Up to 200 gauss | Within 6 inches |
| MRI machine | Thousands of gauss | Multiple feet |
| Handbag magnetic closures | 20 to 60 gauss | Direct contact |
| Hair dryer / power tool motors | Moderate | Within 12 inches |
How Much Magnetism Affects a Watch
Standard automatic watches tolerate around 60 gauss without noticeable timing change. Above that, accuracy starts to drift. Modern antimagnetic watches like the Rolex Milgauss, Omega Master Chronometer line, and IWC Ingenieur are rated to 1,000 gauss or higher.
For the rest of your collection, assume 60 gauss is the effective limit. Avoid sustained exposure above that level.
Symptoms of a Magnetized Watch
Three signs.
Watch running fast. If accuracy drops by 30+ seconds per day suddenly, magnetism is the likely cause.
Erratic timing. Running fast some days, slow others. Typical of partial magnetism.
Watch stopped for no apparent reason. Severe magnetism can stall the balance wheel.
How to Test for Magnetism
Two methods.
Compass test. Hold a compass near the watch. If the needle moves, the watch is magnetized. Simple but detects only severe cases.
Timegrapher. A watch timing machine detects subtle magnetism by measuring rate variation. Most watchmakers have one.
Smartphone magnetometer apps. Measure field strength around the watch. Less precise than dedicated tools but useful for identifying household sources.
How to Demagnetize a Watch
Demagnetizers are cheap ($20 to $50) and effective. Place the watch in or near the demagnetizer, activate it for 2 to 5 seconds, and the magnetic field is neutralized. Most watchmakers offer free demagnetization as a service.
After demagnetization, the watch should return to normal accuracy within hours.
Preventing Magnetism in Storage
Three practices protect stored watches.
Keep watches at least 6 feet from speakers, large motors, and magnetic closures.
Store watches in shielded safes or cases if you live near electromagnetic sources. Some premium safes include mu-metal shielding.
Check periodically. Annual demagnetization is cheap insurance for stored collections.
Winders and Magnetism
Quality watch winders with Mabuchi motors have low magnetic signatures at the motor. The field at the watch position is typically under 5 gauss, well below the threshold that affects accuracy.
Cheap winders with unbranded motors can have significantly higher stray fields. This is one of the practical reasons to avoid sub-$200 winders, beyond just the reliability issue.
For collectors concerned about any magnetic exposure, magnetic levitation winders use fundamentally different technology. See our magnetic levitation winder technology guide for details.
Vintage Watches and Magnetism
Vintage watches are more susceptible to magnetism than modern ones. Older hairsprings used materials more affected by fields. Antimagnetic treatments are recent.
If your collection includes vintage pieces, take extra care with magnetic source placement and consider shielded storage.
Frequently Asked Questions
Can a phone magnetize my watch?
MagSafe-era iPhones and similar magnetic closures can magnetize a watch if kept in direct contact for extended periods. Don't sleep with a phone on your wrist.
Will magnetism damage my watch permanently?
No. Demagnetization fully restores accuracy. The movement isn't physically damaged.
How do I demagnetize at home?
A demagnetizer unit for $20 to $50 handles the job. Activate for a few seconds with the watch inside. Most watchmakers offer the service for free.
Are antimagnetic watches worth the premium?
For active lifestyles with strong magnetic exposure (hospitals, industrial environments), yes. For typical office and home use, no.
Can a watch get magnetized in a safe?
If the safe is near a magnetic source, yes. Steel safes don't block magnetic fields. Mu-metal shielding does.
Does bi-annual demagnetization help?
As preventive maintenance, yes. Small accumulating magnetism resets to zero, keeping accuracy tight.
Is 60 gauss really the threshold?
For standard automatics, roughly yes. ISO 764 tests watches at 4,800 A/m (about 60 gauss). Above that, timing is affected.
Protect and Test
Keep watches away from strong magnetic sources. Test periodically with a compass or timegrapher. Demagnetize if accuracy drifts. For stored collections, a quality safe with shielding and the Virtuoso Series for rotation pieces keeps magnetic exposure minimal.
Related reading: how to store watches long-term, humidity control, and magnetic levitation winder technology.
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