Dr. Ito's In-Depth Analysis of Mechanical Watches! Vol. 41 - Anti-Magnetic Countermeasures for Luxury Watches

Good evening, everyone!

This column, which discusses mechanical watches from an engineer's perspective, is now on its 41st installment. This time, we will be focusing on:

"Anti-magnetic Measures in Luxury Watches"

We'll be discussing this topic.

"Magnetization" has always been one of the top causes of malfunctions in luxury watches, both in the past and today.

In modern life, surrounded by electronic devices, there are many cases where watch maintenance is required due to magnetism. Perhaps some of you are wondering what actions should be avoided.

This time, we will be discussing such "magnetism."

What is magnetization?

As the name suggests, magnetization is a state where parts inside the watch become magnetized, adversely affecting its normal operation.

This is because some of the parts that make up the movement are made of metal that is susceptible to magnetism. Metals, by nature, tend to stick together like magnets when exposed to magnetism, and this property remains even after they are removed from the source of magnetism.

In other words, magnetization in a watch refers to a state where the parts inside the watch retain magnetic properties as a result of the watch coming into close contact with a source of magnetism.

So, what kind of malfunctions can occur if a watch becomes magnetized?

The most common symptom is inaccuracy. The hairspring, which controls the accuracy of the watch, is highly susceptible to magnetization. Therefore, if it becomes magnetized (acquires magnetic properties), it will lead to irregularities in accuracy.

The hairspring is one of the components that make up the balance wheel, the heart of the watch. It expands and contracts repeatedly to keep accurate time, but if it becomes magnetized, its expansion and contraction will be disturbed, and the balance wheel will no longer be able to keep accurate time. This makes the accuracy more likely to go awry, which is a typical symptom of magnetization.

Regarding this accuracy defect caused by magnetization, we have explained it using a real watch in a past YouTube video, so please check that out as well.

In the case of automatic watches, magnetization can also lead to issues such as reduced winding efficiency or a feeling of resistance when winding the watch manually with the crown.

Once a mechanical watch has been magnetized, it will not return to its original state unless it is de-magnetized using a special demagnetizer.

What is an anti-magnetic watch?

So, what measures have luxury watch manufacturers taken against such troublesome magnetism?

1. Magnetic shielding

There are two main methods to make a watch anti-magnetic. The first is to house the movement in a magnetic shield.

The mainstream material for magnetic shields, "soft iron," has soft magnetic properties, meaning that the residual magnetism is very small, and magnetization does not persist after the external magnetic field is removed. The method of using a soft iron case to cover the movement has proven its effectiveness historically, but it has the drawbacks of increasing case thickness and preventing the use of a transparent case back (display case back).

2. Use of non-magnetic materials

To overcome the drawbacks of anti-magnetic watches that use magnetic shields, manufacturers have recently focused on developing "non-magnetic materials."

The problem of magnetism is often solved by using highly non-magnetic materials for the hairspring. Examples include silicon, Rolex's Parachrom hairspring, which uses niobium and zirconium, and silicon-based Syloxi hairsprings.

Representative anti-magnetic watches

1. Seamaster Aqua Terra

In 2013, Omega launched this 'Aqua Terra' as the world's first "truly" anti-magnetic watch in its 'Seamaster' collection. Gauss is a unit of magnetic flux density, and the "Cal.8508" movement installed in this model has been proven to withstand magnetic fields up to 15,000 Gauss, as confirmed by METAS testing. This high level of anti-magnetic performance is due to the adoption of a silicon hairspring. Omega has consistently used silicon hairsprings to this day. 

2. Rolex Milgauss

The Rolex Milgauss, which was discontinued in 2023, is a watch named after "gauss," the unit of magnetic flux density. The first model, introduced in the 1950s, adopted a classic anti-magnetic structure using a soft iron inner case. When it reappeared in 2007, it was also equipped with Rolex's highly anti-magnetic Parachrom hairspring. 

Rolex does not disclose the exact anti-magnetic rating, but it boasts a level of anti-magnetic performance that significantly exceeds the "1,000 Gauss" implied by its name.

3. IWC Ingenieur Automatic 40

The current model of the IWC Ingenieur, the Ingenieur Automatic 40, employs the proven soft-iron inner case construction, similar to the 1950s models. For this reason, while IWC typically prefers display case backs, this model features a closed case back.

Summary

How was it?

Magnetism, an invisible force, is always a source of anxiety. While it is an enemy of luxury watches, many manufacturers have recently released models with improved anti-magnetic performance. So, if you want to use your watch without worrying about magnetization, perhaps these models could be an option for you.

I hope this article has provided you with valuable information and sparked even a little interest in luxury watches! Also, if you have any questions, please feel free to ask us directly, and we will be happy to answer them. We look forward to your visit and inquiries.

Stay tuned for the next installment! See you then!