How to tell that your watch is magnetised
When a watch is magnetised, it usually shows this through a single, very conspicuous symptom: it suddenly runs distinctly fast, often several minutes per day. The gain appears for no obvious reason; the watch was still running normally the day before and now clearly runs ahead. This very abrupt change from reliable to running strongly fast is the classic warning sign.
It is also typical that the rate does not stay constant. Depending on the position the watch is lying in or how you wear it, the gain can be larger at times and smaller at others. This is because the magnetised coils of the spring stick together to different degrees depending on orientation. Erratic behaviour like this points to magnetism more strongly than a steady, small rate error.
With quartz watches the effect is different, because no mechanical spring system sets the beat there. A strong field can briefly block the stepper motor, so that the watch stops or jumps, but after the magnet is removed it often carries on by itself. For the mechanical automatic and hand-wound watches this page is about, however, the sudden gain remains the most important identifying feature.
Why a magnetised watch suddenly runs fast
The heart of every mechanical watch is the balance wheel with its fine hairspring, which contracts and opens again evenly. In the vast majority of classic movements, this spring is made of a steel alloy, and steel can be magnetised. When the spring becomes magnetic, neighbouring coils attract each other and touch at tiny points instead of breathing freely.
When the coils stick together, the effective length of the spring is shortened. A shorter spring oscillates faster, and a faster oscillating balance drives the gear train too quickly. The result is the gain described, which can range from slightly fast to several minutes a day. That is why a sudden gain, and not running slow, is the telltale sign of magnetism.
It is important to know that nothing is broken in the process. Magnetisation is a physical state, not a mechanical defect, and it can be completely reversed. As long as the field sits in the movement, the watch runs incorrectly; afterwards it works as before. If you understand this, you will not panic at a sudden gain but will approach the matter calmly.
Typical everyday sources of magnetism
Magnetism lurks more often than many people think, because modern households are full of small, strong permanent magnets. What matters here is less a fleeting moment than direct contact or a very small distance over a longer time. If you know the typical sources, you can often tell after a brief think where your own watch picked up its field.
| Magnet source | Where it lurks | Risk |
|---|---|---|
| Speakers, soundbars | Shelf, desk, car door | high, strong permanent magnets |
| Phone cases and tablet covers with magnetic closure | Trouser pocket, bedside table | high, often direct contact |
| Bag and wallet clasps | Handbag, jacket | medium to high, easily overlooked |
| Headphones and in-ear headsets | Bedside table, bag | medium, small neodymium magnets |
| Fridge magnets, magnetic boards | Kitchen, office | medium, only when placed directly on it |
| Induction hob | Kitchen | medium, only at very close range |
| Magnetic tools, screwdrivers | Workshop, hobby corner | medium to high on contact |
Strikingly often the phone case is the culprit, because with its magnetic closure it lies right next to the watch in the pocket. The bedside table is also a tricky spot if headphones, phone and watch lie next to each other for hours. A conscious look at your own storage and wearing routine solves many puzzles before you even get to the watchmaker.
Why modern movements are less sensitive
Whether a movement counts as antimagnetic is governed by the standards ISO 764 and the German DIN 8309. They require that a watch withstand a field of 4,800 A/m, which corresponds to around 60 gauss, and afterwards deviate by no more than 30 seconds per day from its previously measured rate accuracy. That is solid everyday protection, but not armour against very strong magnets. For stronger fields, the standard provides a higher resistance class.
Modern movements have long gone far beyond this. Instead of the sensitive steel hairspring, many manufacturers now fit hairsprings made of silicon or of special paramagnetic alloys. These materials can hardly be magnetised, or not at all, because they simply do not retain a magnetic field. If you wear a movement with a silicon hairspring, you will as a rule no longer have problems with the everyday magnets from the table.
A look at the extremes shows how great the progress is. The historic Rolex Milgauss bears its name because it was designed for a thousand gauss, an exceptional figure for its time. Omega's Master Chronometer certification, tested by the Swiss Federal Institute of Metrology METAS, even demands resistance to 15,000 gauss, measured on the finished movement fitted in the case. Such watches need not fear phone cases and speakers. You can find more background on movements and materials in the watch knowledge section of TopWatchReviews.
Self-check with a compass or compass app
You can check a rough suspicion yourself at home, and a simple compass or your smartphone's compass app, which uses the built-in magnetic sensor, is enough for that. Lay the compass flat, wait until the needle is still, and slowly bring the watch closer. If the needle swings clearly or trembles as soon as you move the watch, that points to a magnetic field in or on the case.
This self-check does have clear limits, though, and you should be honest with yourself about them. At best it shows that magnetism is present somewhere, but not whether the hairspring is really affected or how strongly. Metal parts of the case or a bracelet with a folding clasp can also move the needle without the movement being disturbed. The compass therefore does not replace a measurement at the watchmaker; it only provides a first indication.
If the gain is unambiguous and the compass also reacts, you have a solid suspicion. If the compass stays calm even though the watch runs strongly fast, a slight magnetisation may still be present that the rough sensor does not pick up. In both cases the same applies: the self-check narrows down the problem, and the final clarification is done by the specialist with the proper measuring device.
Demagnetising at the watchmaker and at home
The good news at the end of the diagnosis: demagnetising is one of the quickest and cheapest procedures in watchmaking. The specialist places the watch on a demagnetiser, briefly activates the alternating field and slowly pulls the watch away while the field is still running. The whole process takes only minutes and as a rule immediately restores the original rate accuracy.
Simple demagnetising devices for home use exist as well, and with careful use they work. The correct procedure matters: you place the watch on the switched-on device, keep the button pressed and only then pull the watch away slowly and straight before you let go. If you let go too early or lift the watch off abruptly, residual magnetisation may remain. You can find such devices in our overview Tools and care.
For valuable, old or unusual watches, going to the watchmaker is still the wiser choice. They dose the field precisely, check the rate afterwards and notice if another problem is behind the gain after all. For a robust everyday watch the home device is a legitimate solution; for the fine pieces of the collection, a specialist hand is worthwhile. Whether your watch needs to run regularly at all is answered by the guide Does my watch need a watch winder?.
Prevention and proper storage
Prevention is easier than repair, and it costs you nothing but a little attention. Consciously keep the watch away from the known magnet sources: do not put it on the speaker, not on the phone case and not next to the headphones. A hand's breadth of distance from a strong magnet already makes a big difference in practice.
For storage at home, a solid watch box or a quiet, magnet-free spot in the drawer is suitable. Make sure that no magnetic clasps from bags or cases rest directly against the case. Our overviews of watch boxes and watch winders help you find a storage place that also protects the watch from dust and knocks. If you travel a lot, carry your watches in a padded travel case rather than loose in your bag.
In addition, when you next buy a watch it is worth looking at the movement fitted. Models with a silicon hairspring or stated magnetic resistance largely take the issue off your hands in everyday life. And if you switch between several automatic watches and topics such as power reserve and winding already occupy you, you will find more practical instructions in the article Winding an automatic watch correctly and in our care series on polishing acrylic glass.