01 · The problemWhat magnetization is.
The hairspring is the regulating component of every mechanical movement: an extremely thin steel ribbon wound in a coil, narrower than a hair, that determines the oscillation period of the balance wheel and — consequently — the accuracy of the watch. It is also strongly attracted by magnetic fields.
When the hairspring is exposed to a sufficiently intense field, the coils attract one another. The ribbon is no longer free to expand and contract regularly: it "bunches up" at irregular points, the oscillation period changes, and the watch's rate goes haywire — not gradually, but suddenly. +40 s/d, +80 s/d, or even +200 s/d in serious cases.
The paradox is that the watch continues to run perfectly: it ticks regularly, amplitude stays normal, beat error unchanged. Without a measuring instrument it's almost impossible to notice until you check the time at the end of the day. The good news: magnetization is almost always reversible in less than a second, with a tool that costs €15.
02 · The sourcesWhat magnetizes a watch.
The field needed to magnetize an ordinary steel hairspring is relatively low — roughly 10-50 mT (millitesla) is enough, well within the range generated by everyday objects. Here are the most common sources:
Smartphones
Internal speakers, vibration motors and antennae generate localised fields. Sleeping with the watch resting on your phone, or keeping both in the same pocket, is sufficient.
Very commonMagnetic cases for tablets and laptops
The magnetic closures of iPad covers, MacBook sleeves and similar concentrate very intense fields. Resting the watch on top is the fastest way to magnetize it.
DangerousSpeakers and subwoofers
The permanent magnets inside speakers are powerful and often overlooked. Resting a watch on a speaker cabinet — even for a few minutes — is a classic mistake.
Often overlookedBags with magnetic clasps
Many everyday bags have magnetic buttons or clasps. A watch in the inner pocket accumulates small doses of magnetism with each use, building up cumulatively.
InsidiousWatch out for: wireless chargers (Qi/MagSafe), magnetic belt buckles, fridge door magnets, and — less obviously — neodymium magnets on Hi-Fi speakers that sometimes decorate desks.
03 · The diagnosisHow to tell if it's magnetized.
The clearest sign is a suddenly anomalous rate: a watch that ran +5 s/d yesterday and +60 today is an almost certain candidate. But not every case is that stark — sometimes the magnetic field isn't strong enough to shift the rate by tens of seconds, producing only a variable anomaly that's hard to interpret.
With WatchScope the diagnosis is fast and free. Run the quick test horizontal (CH): if the rate is far higher than usual, be suspicious. Then run the 5-position COSC test: a magnetized watch shows a very high horizontal-to-vertical delta — typically >40-50 s/d — because the way the coils attract each other changes radically as the field orientation shifts relative to gravity. A normal watch has an H-V delta of 5-15 s/d.
A quick alternative without the app: bring a compass (even your phone's) close to the watch. If the needle points at the movement instead of north, the residual magnetic field is strong enough to confirm magnetization.
Remove the watch from your wrist, rest it on a wooden surface, wait a minute and retest. If the rate changes drastically — e.g. from +70 s/d on the wrist to -5 s/d on the table — it's magnetized with near certainty. The hairspring responds differently to Earth's field depending on how it's oriented relative to the residual magnetization direction.
04 · The fixHow to demagnetize: less than a second.
An AC demagnetizer generates an oscillating field that, as it decreases to zero, brings all the magnetic domains in the hairspring to a neutral position — erasing the magnetization without disassembling anything. Find one on Amazon for €15-20 by searching "demagnetizer watch" or "watch demagnetizer". The process:
- Switch the demagnetizer on and bring the watch close to the coil (touching or 1-2 cm away).
- Keep the button pressed and slowly move the watch away to 50-80 cm distance (take 5-10 seconds to pull back gradually).
- Release the button only once the watch is already at distance — don't switch the tool off while the watch is still nearby.
- Verify with WatchScope: the rate should be back in normal ranges. If not, repeat once more.
No need to open the watch, no need to visit a watchmaker, no need to touch the movement. The process also works with the watch on your wrist (though it's easier to hold it in your hand).
In very rare cases the demagnetizer doesn't fully resolve the issue. This means structural components other than the hairspring are also magnetized — steel wheels, pallet fork, pinions. In that case a watchmaker is needed; they'll partially disassemble the movement and demagnetize individual components one by one. Rare, but possible with watches exposed to very intense fields (e.g. near neodymium magnets for hours).
05 · PreventionHow not to let it happen again.
Magnetization is easy to fix but even easier to avoid. A few habits are enough:
- Distance from speakers: at least 20-30 cm between the watch and any speaker or subwoofer, even at low volume.
- No watch on charging devices: wireless Qi/MagSafe chargers, active powerbanks — keep them away from your wrist or bedside table when the watch is there.
- Anti-magnetic watches (ISO 764): the standard certifies resistance of 60,000 A/m. Known models: Omega Aqua Terra, IWC Ingenieur, Longines L2 COSC. A soft-iron inner cage shields the movement from external fields.
- Silicon hairspring: movements with silicon hairsprings (Rolex Parachrom blue, Omega SILINVAR, Patek silicon) do not permanently magnetize, by the nature of the material. It's the definitive solution.
More and more manufactures are adopting silicon or non-ferrous alloy hairsprings (Glucydur, Nivarox grades). On these movements a demagnetizer is literally useless — but also pointless. If you're choosing a watch to wear in environments with many electronic devices, checking the hairspring material is a concrete consideration.
Run the test now,
for free.
WatchScope shows the rate in real time. If you see +40 s/d where +5 used to be, you already have the diagnosis. Download the app and check before booking a watchmaker.