ALL ABOUT: Watches and magnetism – The history of magnetic resistant watches

Tags: FAQ | Technology and concepts | Classic

4.8.2021 | 8 MIN | 2x comment

Our mechanical watches are surrounded by all kinds of magnetic lures. Board inductions, iPhones, magnets in handbags, household electrical appliances and so on. This is how watch brands massage us in an effort to push their antimagnetic watches. But this problem is certainly not a 21st century issue. What is the history of magnetic resistant watches, what innovations has the fight against antimagnetism brought, and what standards must a magnetic resistant watch actually meet?This will be the second part of the Watch and Magnetism series.

The first part of the series Watches and Magnetism:

What kind of watches are considered magnetic resistant?

Quite simply and in general, magnetic resistant watches are those that run with minimal or ideally no deviation when exposed to a certain magnetic field strength.

If watch manufacturers want to get certified for antimagnetic characteristics, they must meet the ISO 764 norm (or the German alternative DIN 8309). By the way, ISO 764 is part of the requirements you need for meeting the norm for diving watches (ISO 6425), so if you have a certified diving watch in front of you, they also have the norm for antimagnetic watches.

International Standard 764 determines test conditions for watches resistant to specific magnetic field strength. The first version of ISO 764 was released in 1973, the 2002 version is now in use, but the 2020 version has already passed the approval process.

For a watch to be marked as antimagnetic, it must withstand a force of 4800 A/m and at the same time do not show a deviation of more than 30 seconds per day.

The standard distinguishes between two types of watches:
a) Magnetic resistant watches designed to withstand a homogeneous and continuous direct current magnetic field of 4 800 A/m encountered on a daily basis.

b) Enhanced magnetic resistant watches designed to withstand a homogeneous and continuous strong direct current magnetic field equal or higher than 16 000 A/m encountered in close proximity.

Testing according to ISO 764 is performed for the first type of watch, ie for normal wear. The watch is placed in a tester and exposed to magnetic field. This field gradually increases up to the tested force (ie 4800 A/m). After that, the watch is monitored for at least 60 seconds to see, if the watch has stopped or not. If the watch does not have a second hand, the tracking time is longer. Then the force decreases again to zero.

The watch is tested without a bracelet (if removable) and the room temperature must be 23 °C ± 5 °C. Mechanical watches are placed in the test device so that the magnetism acts in the direction 3H-9H, ie horizontally with the dial. With electronic watches, the tested motor has to be exposed to magnetic force as directly as possible.

During the period of exposure to the magnetic field, the watch must not stop, and go through any other changes – it must not affect the operation of the chronograph, calendar, or, for example, there must be no sticking of hands, etc. For electronic watches with multiple motors, none must stop. The deviation of the watch after the exposure to the magnetic field must be a maximum of ± 30 s/day.

With magnetic resistant watches we usually deal with units Amperes per meter or Gauss. The conversion is 1 Gauss = 80 A/m.

The history of magnetic resistant watches

As I mentioned before, magnetic resistant watches are not a novelty the 21st century. The need for magnetic resistant watches took place in the 20th century and it grew more and more with the expansion of railway networks and aviation. Requirements for watches for American railway workers have included since the 1940s, among other things, resistance to magnetism. And for aviators, the need for a magnetic resistant watch was just as intense, because the watch had to withstand the magnetic interference of instruments on the dashboard.

Vacheron Constantin began developing magnetic resistant watches at the end of the 19th century. In 1915, he introduced the world's first magnetic resistant – at that time still pocket – watch.

The primacy of wrist magnetic resistant watches is given to Tissot. Tissot introduced them in 1929, launched them in 1930. And called them aptly Antimagnetique.

In the 1940s, the IWC developed a magnetic resistant watch for the Royal Air Force. The British Air Force needed a watch that would be resistant to interference from Spitfires and Huricane aircraft engines. The IWC came up with a Mark XI watch that resisted magnetism using a so-called Faraday cage.

Faraday's cage makes a protective layer commonly made of soft iron, which is a great conductor, and is able to contract the magnetic interference on itself, so that the movement itself remains protected. As ingenious as this solution was, it was no longer very elegant. Because it had to have a closed casing, the watch usually couldn't display the date, or for the watchmaking lovers, there wasn't a view of the movement. However, this protection, sometimes also called Mu-Metal (most commonly an alloy of nickel and iron) is still used today.

Rolex Oyster Perpetual Milgauss is without a doubt one of the most well-known magnetic resistant watches. The first Milgauss with the mark 6541 was introduced by Rolex in 1956 and withstood the magnetic force of 1000 Gauss. Hence the name: mille is a thousand French, Gauss is a unit for magnetic force. Rolex ended the production of this watch in the late 80's, so the original models are quite a sought-after collector's item. It relaunched the watch with a second hand in a shape of a lightning in 2007.

Rolex Milgauss became famous mainly for being worn by CERN employees in Geneva, as Rolex purposefully produced several pieces for them in 1954.

At that time, Rolex Millgauss became an ideal choice for employees of a nuclear research organization and also aviators, physicians and other professions. Rolex achieved high resistance with the already mentioned Faraday cage, but also thanks to the use of paramagnetic materials for the 3131 movement. It was a first watch with such high resistance to magnetism. Conventional magnetic resistant watches usually reached values ​​around 50–100 Gauss.

Similar results were achieved by the IWC in the Inginieur Ref. 666. model in 1955. Omega then followed with the Railmaster CK2914 model with 900 Gauss resistance, which was introduced in 1957.

IWC Ingenieur, Source: monochrome-watches.com

The Quartz Revolution overshadowed the fight for magnetic resistant watches a little, but in fact they never died down. And today, this topic is stronger than ever. In 1989, the IWC came up with a ref. 3508, able to resist 6250 Gauss.

The  Omega Seamaster Aqua Terra with a resistance of 15,000 Gauss, which Omega introduced in 2013, is considered to be the first truly fully magnetic resistant mechanical watch. Omega no longer relied solely on a metal shield in the form of a Faraday cage, but focused on the development and use of materials for its movements, which are naturally antimagnetic. It was mainly the ability of silicon to resist magnetic effects on a fiber.

The usage of antimagnetic characteristics of silicon has proven to be a viable and cost-sustainable way, and Omega has used silicon fiber for its other models. Nowadays, almost all of Omega watches have been certified by the METAS company, confirming that the watch is resistant to 15,000 Gauss.

Antimagnetic materials are used across brands in the Swatch Group. Silicon-based fibers can be found, for example, in Tissot (see for example Tissot Gentleman), Mido (for example, the beautiful Mido Baroncelli) or Hamilton (eg Hamilton Khaki Aviation). In Hamilton, you can tell the movement has a silicon fiber by the name of the movement (for example, H-21-Si for the mentioned pilots), often stated by the manufacturer on the view of the movement (for example, Mido, Tissot), or in a less tasteful design directly on the dial (Tissot).

Certina picked titan over silicon, which also has excellent magnetic resistance. A fiber from the Nivachron material can be found in all of the new watches released since 2019.

A magnetic resistant specialist is also the brand Ball. Most of their watches reaches magnetic resistence of 4800 A/m, those with the Mu-metal protection even 80 000 A/m.

Ball Engineer Master II Aviator with magnetic resistance of 80 000 A/m.

The most well-known types of alloys used for movements:

Elinvar is an alloy of nickel, iron and chromium, patented by Hamilton in 1931. The discovery happened thanks to Swiss scientist Charles E. Guillaume. The name then comes  from "Elasticity Invariable". The advantage was that the alloy did not show changes during temperature changes and was also almost non-magnetic. Hamilton used Elinvar mainly for a fiber in mechanical watches.

Invar is an alloy of iron and nickel (36% and 64% with an admixture of carbon and chromium), invented by physicist Charles E. Guillaume in 1896, who even received a Nobel Price for this discovery in 1920. In watches, it was used as a base of alloy by eg Patek Philippe (Silinvar) or Hamilton (Elinvar). It better withstood the influences of magnetism and temperature changes.

NivaGauss is a silicon-based alloy, but the exact composition is the trade secret of Omega. Omega started developing it earlier when the Si14 material for fiber was introduced in 2008. Currently, Omega used magnetic resistant material in all of their Co-Axial calibres.

Nivachron™ is a patented alloy developed by Swatch group cooperating with Audemars Piguet and Certina. It was first used in the Swatch Flymagic watch. Certina introduced it in the Certina DS-1 Big Date 60th Anniversary model in 2019 and then in all of their watches since then. It is based on titanium, which is naturally highly resistant to magnetism.

Nivarox is an alloy of nickel and iron, invented in 1933 by Reinhard Straumann. Similarly to Elinvar, for example, it has excellent constant properties with temperature changes and resistance to magnetism. It is now used as a trade name by Nivarox, a company belonging to the Swatch Group. The composition varies according to use, but the basis is iron and a high percentage of nickel (30–40%), then there is molybdenum, beryllium, titanium, chromium, silicon and more.

Parachrom, or Blue Parachrom is an alloy patented by Rolex. It has a typical blue color and is mostly magnetic resistant, but also resistant to temperature changes. Rolex says that a Parachrom fiber is almost 10× more shock resistant than common fibers.

Blue Parachrom is a magnetic resistant alloy from Rolex.

Silinvar® is a patented alloy of Patek Philippe. The name comes from words silicon and  invariable. The basis is an alloy of nickel and iron Invar, which Patek began to use after its discovery at the end of the 19th century. From Silinvar, Patek created, for example, the Spiromax fiber used in his calibres.