Did you know that something as simple as using a cell phone (especially with a rechargeable cell phone cover), going through airport security and even flying can affect the accuracy of your mechanical watch? Microwaves, handbags with magnetic closures, certain electrical instruments and some medical testing equipment can also have a negative impact on your mechanical timepiece.
Essentially, when a watch that is not deemed "anti-magnetic" comes into contact with a magnetic force field, the inner escapement of the watch can stutter, causing a slight-to-moderate impact on timing accuracy. Some people have reported that in certain instances, their timepiece just stops working. This is why certain watch brands take steps to ensure that their watches — especially pilot watches that are exposed to magnetic fields when flying — are anti-magnetic.
The concept of anti-magnetism in watches was first developed back in the 1930s when military pilots had issues with their watches stopping or becoming inaccurate. Generally, IWC Schaffhausen is credited with developing the first-ever anti-magnetic watch, and it did so by building a soft iron inner case that could reside within the outside case, but cover and protect the movement parts that were made of metals affected by magnetism. For decades, that inner iron case was the only way watch brands could find to protect the movements, and certain brands developed their own inner anti-magnetic iron cases — predominantly for pilot watches.
In recent decades, though, the use of high-tech alloys in watch movements have helped to render these watches anti-magnetic. These alloys include silicon, Glucydur, Elinvar and more. When mainsprings, escapements and hairsprings inside the watch are made of these materials, the watch becomes anti-magnetic without needing an iron inner case to protect it.
Essentially, an anti-magnetic watch can run with minimal deviation in time tracking when exposed to magnetic fields. The International Organization for Standardization has issued a standard for magnetic resistant watches: ISO 764 Horology - Magnetic. It states that a watch must keep its accuracy to +/- 30 seconds a day to be deemed magnetic resistant.
If you are continually exposed to magnetic fields, and have not experienced any timing issues with your mechanical watch, bravo. If you have had some issues, stop in any time to let us help you find the right watch for your wrist that is anti-magnetic and still suits your personal tastes.