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Magnetism and Watches

written by A.Morgan - 27th Apr 2011

Magnetism is everywhere. It has the power to lift enormous weight, generate electricity, make objects hover – it also protects Earth from the gigantic forces unleashed by the sun in the form of solar winds.

Solar winds sound very tranquil, but are in fact the ejection of vast amounts of electrons and protons from the sun in what is essentially a nuclear explosion. These winds travel at 750 kilometres per hour, and would wipe all life of the face of Earth instantly, were it not for magnetism.

The Earth’s magnetosphere is perfectly formed to deflect the winds away, like two magnets repelling each other. Instead of total annihilation, instead we see various Auroras, such as the Northern Lights.

As well as natural magnetism, man-made magnetism is also present. Electrical machinery generates a magnetic field, as discovered in 1819 by Hans Christian Ørsted, completely by accident. He realised that an electric current could influence a compass needle, and this discovery encouraged the work of André-Marie Ampère, Carl Friedrich Gauss and Michael Faraday to begin.

Ampère furthered Ørsted’s work, establishing in greater detail the behaviour of electricity and magnetism, demonstrating that similar and opposing currents would attract and repel each other. Gauss also ventured into studies in magnetism, measuring the intensity of the Earth’s magnetic field and discovering the difference between the magnetic field generated by the Earth’s core and its magnetosphere. Faraday pushed the understanding of magnetic fields even further, observing its effect on light, and discovering how to insulate from it. The development of his Faraday Cage became the basis for antimagnetic protection in many devices, including watches. His work was so highly regarded that Einstein kept a picture of him on the wall of his study.

Magnetism and gravity, although similar, are quite different. Gravity is the effect of two bodies upon each other based on their mass, whereas magnetism only affects materials that are magnetic. By bad luck and coincidence, the contents of a watch movement are made of paramagnetic materials, or in other words, materials that are affected by magnetic fields. Electronic equipment can often produce large magnetic fields, and so the combination often proved fatal for an unprotected watch.

Vacheron Constantin tinkered with the idea of an antimagnetic watch in 1846, and Tissot manufactured the first using non-magnetic materials for the movement in 1930. The materials, including Invar and Elinvar, developed by Nobel-winner Charles Edouard Guillaume, lead to the non-variable, non-oxidising alloy Nivarox, used in most Swiss movements for the hairspring and mainspring.

The 1955 IWC Ingenieur took those antimagnetic properties to another level, encasing the entire movement in a soft iron Faraday cage. This, in the Ingenieur’s most protected form, gave magnetic protection of 500,000 amperes per metre (A/m), enough to resist an MRI scanner.

Rolex also tried their hand at antimagnetic watches with the Milgauss. Able to resist one thousand Gauss (about 80,000 A/m), it too has a soft iron Faraday cage around the movement.

On launch the looks of both the Ingenieur and in particular the Milgauss made them both quite unpopular. Anti-magnetic watches have never really had much of a use outside of a laboratory, and unlike divers’ watches or pilots’ watches they don’t have an adventurous attraction to them. They have managed to corner themselves into a niche that no one had a use for, and it has been the collectors, who seek the original rarity of these models, that have influenced their desirability enough to bring these odd watches back into the limelight. This reinvigoration sparked updates from both IWC and Rolex (although not until very recently by Rolex) and the Ingenieur and Milgauss names live on, for now. So much discovery and science goes on inside those cases that it would be a shame to lose them.