How Magnets Can Ruin Your Watch (And What You Can Do About It)

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How Magnets Can Ruin Your Watch (And What You Can Do About It)

Words by Mr Alex Doak

17 July 2020

Since the dawn of the electronic age, magnetism has been public enemy number one to the humble mechanical watch. Shocks, water, dust and mud were all addressed as soon as timekeeping migrated from the pocket to the wrist just after WWI. But proximity to electric motors or even the smallest magnets has always troubled the tiny components ticking inside your watch. If your watch is running fast, slow or has stopped altogether, there is a reasonable chance that a magnet is to blame.

All the more so these days, unfortunately, thanks to the ubiquity of mobile phones, television and PC speakers, microwaves, magnetic necklaces, handbag clasps, hairdryers, electric razors, magnetic parts of refrigerators… They all contain strong magnets or tightly coiled solenoids of wire, which create magnetic fields when electric current passes through them (your basic electric motor).

Watchmakers have not shied from the fight. Far from it. From miniature Faraday cages to increasingly innovative alloys and, lately, replacing metal altogether with silicon, the pursuit of anti-magnetism – much like the pursuit of water resistance – has evolved into an arms race.

01. Why are magnets so bad for watches?

Magnetic fields are not permanently damaging to your timepiece, but they can affect its accuracy or even stop the watch completely. This is chiefly down to the vulnerability of the balance spring, whose four-times-a-second compression and expansion regulates the steady tick of your watch’s mechanics. If this hair-thin coiled spring of metal alloy becomes magnetised, it will stick to itself, which will make your watch run fast, slow or stop.

Steel components in your watch are even more sensitive to magnetism and, if magnetised, can create magnetic fields inside the movement, which perpetuates the problem.

02. How watches combat magnetism

Watches have been battling magnetism since the 19th century. Up until the 1940s, companies were experimenting with materials that could be used for movement components instead of ferrous steel and brass. The exact origins of the anti-magnetic watch are difficult to track down, but many signs point to a non-magnetic, palladium-made escapement patented by Mr Charles-Auguste Paillard in the mid-1880s.

By 1888, IWC SCHAFFHAUSEN had produced a non-magnetic watch movement for the Non-Magnetic Watch Company. The balance wheel, balance spring, escape wheel and pallet fork body were made from a palladium alloy, the fork from bronze and its arms from gold. Then, in 1896, Mr Charles Édouard Guillaume discovered the nickel-based alloy Invar (iron-nickel-carbon-chromium), the first of a long list of anti-magnetic alloys, including Nivarox (iron-nickel-chromium-titanium-beryllium alloy) and Glucydur (beryllium-bronze alloy), which are still used extensively, but don’t provide complete protection.

Then came IWC’s invention of physically shielding the movement with a highly permeable, or magnetically conductive, material. Made for RAF pilots, the Mark 11 (made by IWC and Jaeger-LeCoultre) had its movement placed in an inner case of soft iron (iron with a low carbon content that is easily magnetised), which acted like a Faraday cage to deflect magnetic fields emanating from cockpit instrumentation. This became standard practice for the watches emerging in the 1950s, most notably the Rolex Milgauss, named after its resistance to up to 1,000 gauss, and IWC Ingenieur.

More recently, the focus has switched back to materials science, with Patek Philippe, Rolex, Swatch Group, De Bethune and Ulysse Nardin’s pioneering efforts in the 2000s – even whizzier non-ferrous metal alloys, totally non-metallic silicon components etched from wafers in laboratory clean rooms and even cultivated diamond. The use of silicon components in a watch’s escapement is protected by a patent that expires in 2021, so expect many more brands to embrace the technology in the near future.

To date, Omega has been the only watch brand to certify its watches to a new standard of magnetic resistance. The Swiss metrology institute METAS certifies its Master Chronometer watches as able to operate in magnetic fields of up to 15,000 gauss.

03. Understanding the jargon

One of the problems for anyone who wants to keep their watch safe from magnetism is the impenetrable numbering systems and lack of practical advice. How are you supposed to know how strong a magnet is? And what on earth is a gauss?

The international standard ISO 764 defines basic magnetic resistance for watches. They must resist exposure to a direct current magnetic field of 4,800 amperes per metre – about the strength of the magnet in your fridge door – and keep precision to ±30 seconds a day. Not very much, in other words.

Even more confusingly, there are two main ways of measuring magnetic field strength and watchmakers use both. The pure strength of a magnetic field is measured in amperes per metre, expressed as A/m. Most watch brands, however, describe their resistance to magnetism in units of gauss. This is a measure of a material’s exposure to a magnetic field, which takes into account the magnetic permeability of the material. Technically, this is called magnetic flux density, and it is also measured in teslas (1 tesla = 10,000 gauss). Told you it was confusing. What you need to know is that the units are convertible – 4,800 A/m is about 60 gauss, 1,000 gauss is about 80,000 A/m and 15,000 gauss (the strength of an MRI scanner) is about 1.2m A/m.

So how to avoid magnetic exposure? Magnets are everywhere. The latest iPad Pro boasts of including 102 of them. Hard drives, headphones, bicycle dynamos and electric guitar pick-ups, to name just a few relatively common items, contain small but powerful neodymium magnets (also known as rare earth magnets). These are seriously strong. A coin-sized magnet can lift 9 to 10kg. Mostly, they are a lot smaller than that and their field strength weakens rapidly after a couple of centimetres (which is common sense, really, if you’ve ever played around with a magnet). To be safe, don’t store your watch on, or next to, anything with a strong magnet inside and think twice before getting it too close to an electric motor in use.

04. What does this mean for you?

Magnetisation is easy to diagnose at home. If you think your watch is running fast or slow, place your watch near a compass. If the compass needle moves, your watch has been magnetised.

Don’t worry. The condition is never permanent. Every service centre has a demagnetising machine, which your watch simply sits on top of for a few minutes. By quickly alternating its electrical current, it randomly scrambles the alignment of any magnetised particles (in simplified terms, magnetic fields occur when charged electrons align), which cancels any net magnetic fields.

Unless you own a watch with a stated level of magnetic resistance (such as a closed-caseback IWC Pilot’s watch) or anything that boasts a silicon escapement, do your best to avoid moving speakers around the house while you’re wearing your mechanical watch, don’t rest it on top of your iPhone cover and take it off for that hospital scan.

Illustrations by Mr Joe McKendry

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