Watch Trays and Magnets: Keeping Mechanical Watches Accurate
Many trays use hidden magnets for lids and catches, but magnetism can upset a mechanical watch. Here is what ISO 764 actually tests, and how to design a watch tray that keeps magnets out of the way.
What magnetism does to a mechanical watch
At the heart of a mechanical watch is a very fine coiled hairspring that oscillates to keep time. Expose it to a strong enough magnetic field and the coils can stick to each other, shortening the oscillation. The watch typically starts running noticeably fast, and keeps doing so after you move it away, until a watchmaker demagnetises it.
Magnets are everywhere in daily life: speakers, tablet covers, bag clasps, and the magnetic catches on trays and boxes. A watch tray is where the watch sits next to that catch the longest, all night.
What ISO 764 tests
ISO 764 is the international standard for magnetic resistant watches. To carry the antimagnetic label, a watch must withstand a direct current field of 4,800 A/m (roughly 60 gauss) and afterwards keep its rate within plus or minus 30 seconds a day of its pre-test rate.
The 2020 edition added an enhanced category from 16,000 A/m upward, and an annex on the relationship with distance from products that generate magnetic fields. The practical takeaway for trays: distance matters a great deal, because field strength drops quickly as you move away from a magnet.
Designing a watch-safe tray
First, the tray or compartment that holds the watch should have no embedded magnets at all. If you want a lid, use a weighted lift-off lid or a hinged one. Second, on a combined tray with several bays where you do want a magnetic lid, put the magnet on the edge furthest from the watch bay, as far as the tray size allows.
Third, do not park the watch tray beside a speaker or a wireless charging pad. A tray with a phone charging slot is convenient, but keep the watch bay on the opposite side from the phone.
A floor that will not scratch
A watch laid face down or on its side on a hard surface picks up marks on the case and crystal. A soft floor, such as nubuck or velvet, makes a real difference. With several watches, separate bays or strap cushions stop the cases knocking together. See our nubuck tray for watches and glasses.
What about quartz?
Quartz watches have no hairspring, but they do have a tiny stepping motor that works by magnetism, so a strong field can disturb them while they sit close to it. The same rule covers every kind of watch: keep it away from magnets. Browse all designs under watch trays.
References
International Organization for Standardization. ISO 764:2020 Horology: Magnetic resistant watches.
Antimagnetic watch. Wikipedia.