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Why Does Anti-Magnetism in Watches Matter?

Omega Seamaster Aqua Terra 15,000 Gauss Bumblebee

From Rolex to Omega to Ulysse Nardin, anti-magnetism is something many a watchmaker likes to boast about, almost as much as water or shock resistance. It’s enough to make it obvious that magnets and watches have a toxic relationship, but it also might have you thinking: why?

The issue comes down to the balance spring. The flat coil of metal sets the pulse of the watch, oscillating back and forth to ensure the escapement regularly releases mainspring energy into the rest of the watch. It’s a necessarily delicate part, responsible for consistent timekeeping, but also the most likely to get an unhelpful dose of magnetism.

Ulysse Nardin Freak Balance Spring

The most common problem is that when it gets magnetised and the coils close in, the metal can stick to itself. This effectively makes it shorter, which in turn makes it oscillate quicker and gain time. Just how big a problem this is depends on the level of magnetisation. A few minutes too close to your phone screen might not have too noticeable an impact; leaving it on a giant loudspeaker will have it running quicker than an Olympic sprinter.

In real terms, it can range from a relatively unnoticeable 15-20 seconds a day to gaining tens of minutes in an hour. If it’s particularly bad, the spring might even lock up, a narcissus unable to resist its own magnetism, stopping the watch completely. This is not good.

It’s not the only problem of course; magnetisation also screws with the spring’s temperature compensation so that a particularly hot or cold day can ruin its timekeeping, and with more complicated watches there are even more things that can go wrong. The balance spring is the most at-risk part of magnetisation but honestly, you don’t want any of your watch getting magnetised.

Watch Demagnetizing Tool

A simple watch demagnetizing tool.

The problem is that avoiding magnets is easier said than done. Sure, those in speakers and motors are relatively big, but tiny, rare-earth magnets are everywhere: phones, laptops, the front of your fridge, everywhere. Fortunately, fixing the issue is surprisingly easy. You don’t need to open the watch, just get yourself a cheap degausser online. Or, if you’re still hanging on to an old CRT monitor, you can use the degaussing function on that, holding your watch up to the screen. Fixed, sorted, disaster averted. Provided you didn’t miss a meeting or two before you noticed, obviously.

Either way, it’s annoying when it happens, especially if you’ve been losing time for days. Even if fixing the issue is straightforward, wouldn’t it be better if it never happened at all? That’s why watchmakers have been trying to head magnetism off at the pass for centuries.

Rolex Milgauss 116400

Rolex Milgauss 116400

There are a few ways to combat magnetism. The old-school way is to include a soft iron inner shell. Patented way back in 1884 by C. K. Giles in Chicago, the inner case shields the more delicate components from magnetic interference. It was an inspired idea but one that, back when there were fewer magnets around, didn’t really impact much. It wasn’t until WWII and magnetising radar systems that anti-magnetic watches became a necessity for pilots, with the legendary Jaeger-LeCoultre and IWC Mk 11 commissioned by the Ministry of Defence in 1948.

CERN Large Hadron Collider

Large Hadron Collider, image credit: CERN

That said, the most famous anti-magnetic watch in existence is the Rolex Milgauss. It’s in the name, after all, designed to withstand magnetic fields of 1,000 gauss. Developed in 1956 for CERN, the European particle and physics lab, it included a Faraday cage to protect itself. Incidentally, Rolex still works with CERN decades later, even if the Milgauss is a bit of an odd duck in its lineup these days.

Of course, the easiest way to deal with magnetism is to make sure your delicate parts can’t get magnetised in the first place. It’s a technique that Vacheron Constantin attempted as early as 1846 by using a palladium balance spring, though it didn’t build its first successful anti-magnetic pocket watch until 1915.

Rolex Milgauss Brochure 1960

Rolex Milgauss brochure cover 1960

Nivarox advertisement from the 50s

Nivarox advertisement from the 50s

The biggest leap in anti-magnetism in watchmaking was the introduction of Nivarox. A much more resistant nickel-iron alloy than steel in every way, it quickly replaced steel in even accessible watches. In fact, it’s still the main balance spring material you’ll come across, but it’s not perfect and can still be magnetised. Unlike silicon.

Zenith DefyLab Silicon Oscillator

Silicon has a ton of chronometric benefits. It’s tougher, never requires lubrication and, while it’s not as easy to adjust, is lighter and harder than steel. It’s also completely anti-magnetic, a benefit that Ulysse Nardin made the most of in the 2001 edition of its phenomenal Freak, the first timepiece in the world to use a silicon balance spring.

It’s so good an alternative that Omega and other Swatch Group brands have embraced it entirely, as have Rolex, albeit a touch more tentatively. It’s expensive compared to Nivarox, so don’t expect to see it in every Sellita or Miyota though.

Omega Seamaster Aqua Terra 15,000 Gauss Bumblbee

All of this however might be overkill. The Rolex Milgauss is resistant to its namesake 1,000 gauss, while Omega Seamaster Aqua Terra is resistant to 15,000. It makes you think those levels of protection are necessary for everyday wear. They’re not. Five gauss is considered a safe level and unless you tend to store your watches in an MRI machine, all you’ll really need is something ISO 764 compliant, which is resistant to 60 gauss

Still, for some collectors there’s no such thing as too much protection. You’re going for a light swim? Best get an Ultra Deep or Deepsea Challenge, then. Over the top claims of elemental resistance are nothing new and, even if it’s fundamentally pointless, it’s still fun to say that your watch can survive an MRI machine. Just hope nobody asks why.

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About the author

Sam Kessler

Legend has it that Sam’s first word was ‘escapement’ and, while he might have started that legend himself, he’s been in the watch world long enough that it makes little difference. As the editor of Oracle Time, he’s our leading man for all things horological – even if he does love yellow dials to a worrying degree. Owns a Pogue; doesn’t own an Oyster Perpetual. Yet.