· By Buffy
Magnetism
The most common modern watch problem and the cheapest to fix: what magnetic fields do to hairsprings, how to test, and how to demagnetize.
A magnetized watch is the great masquerader: it can gain minutes a day, stop, restart, and behave like a dying movement — and the fix takes ten seconds with a $15 tool.
What actually happens
The balance spring is a coiled spring; if it becomes magnetized, adjacent turns cling together. Effective spring length shortens, the balance oscillates faster — sometimes much faster (minutes a day) — and coils may visibly clump. Steel parts (hairsprings in older watches, some screws) are the victims; Nivarox alloys resist but aren’t immune; silicon springs (Si14, Syloxi, Spiromax) are effectively immune.
Where the fields live
Laptops and tablet covers (magnetic clasps), handbag snaps, speakers, headphones, magnetic phone mounts, refrigerator magnets, airport scanner tables, some travel pillows. You don’t need an industrial magnet — the ubiquity of small permanent magnets in modern life is the whole story.
The fix
Demagnetization: pass the watch through a strong alternating field that decays to zero (the classic blue demagnetizer gadget, or a watchmaker’s demag unit). It takes seconds and costs almost nothing. If the watch returns to normal rate afterward, that was the problem.
Prevention: keep distance from magnetic closures and speakers; choose movements with modern springs if your life is magnetic (Omega Master Chronometer pieces are certified to 15,000 gauss; Rolex Parachrom, silicon-spring ETA/Sellita variants, and Seiko’s modern springs all resist strongly).
What magnetism is not
It is not permanent damage (in steel-spring watches it’s reversible), it is not “battery” (there is no battery), and it does not need a service — unless you’ve had the watch magnetized repeatedly and something else is worn. Test with a cheap compass or a phone app first; service second. See also Friction and Lubrication for the failure it imitates.