Looking around the 60th floor penthouse of the Setai Building in New York yesterday, it was easy to see this was no ordinary watch press conference. It was a full house –packed with enthusiasts and mainstream consumer press alike –and then, there were the presenters. Jean-Claude Monachon, head of product development for Omega; Michel Willemnin, CEO of Swatch Group R&D house ASULAB; Thierry Conus, director of R&D for ETA; and, the biggest of the big guns, Stephen Urquhart, global CEO of Omega.
The conference was to officially introduce us to Omega’s latest technology advance –the already-much-discussed Omega Aqua Terra >15,000 Gauss. The watch is not so much resistant to magnetism as it is simply immune to it –by incorporating a number of different materials innovations, Omega’s succeeded in making a watch that can withstand magnetic fields far stronger than anything you’re ever likely to encounter outside an MRI machine (or maybe the Large Hadron Collider.)
Is magnetism a problem in watchmaking? Indeed it is, and more so now than ever, thanks to the ubiquity of small, powerful magnets in everyday life. Small but extremely powerful permanent magnets are everywhere –iPad cases, clasps for purses; catches for cell phone cases –even your innocent looking refrigerator magnets are just waiting to tie your watch in knots.
Some math: 0.1 tesla=1000 gauss; a fridge magnet, we were told, has about a 0.1 tesla strength field, which is more than enough to mess up the rate of a watch. 1 gauss is also equal to about 10^3 amperes per meter. Different units are used by watchmakers, as well as scientists and engineers, because there are two separate but related types of magnetic fields –the so-called B field and the H field. B fields are those generated by electric current flow; while H fields are those found in magnetic materials which themselves contribute to the magnetic field strength. Tesla/gauss units are used to measure B fields, while oersted/amperes per meter are used to measure H fields.
To be officially rated “anti-magnetic” according to ISO standard 764, a watch must be able to resist a direct magnetic field of 4,800 A/m.
The usual method for making a watch anti-magnetic is to surround it with a shield of either mu-metal or soft iron (mu-metals are a group of nickel-iron alloys used for anti-magnetic shielding.) In both cases, the protective shield –usually taking the form of an inner case around the movement, topped with a dial of the same material –has high magnetic permeability —that is to say, it provides a preferred pathway for a magnetic field. (It’s not, it’s worth noting, because it’s a Faraday enclosure –a Faraday enclosure is a conductor of electric current. Aluminum, for instance, can be used to make a Faraday enclosure, but will not protect against magnetic fields.)
In 1957 Omega introduced its Railmaster line of watches, so named because they could be used by workmen crewing diesel-electric locomotives. The Railmaster had a magnetic resistance rating of 900 gauss, and used a mu-metal inner case. The famous Rolex Milgauss gets its name from its magnetic resistance –it’s capable of resisting a field of about 80,000 A/m, which corresponds to a magnetic flux of 1,000 gauss. Significantly, this is also about the upper limit of protection that can be provided by a ferromagnetic inner case.
The most anti-magnetic –or amagnetic, perhaps, would be a better word –watch of all time was until very recently the IWC Ingenieur 500,000 A/m. Unlike other anti-magnetic watches, it relied not on mu-metal or soft iron shielding, but on non-ferromagnetic materials –most notably, a balance spring made of a niobium-zirconium alloy. The balance spring, however, proved to be both the greatest strength and greatest weakness of the watch –introduced in 1989, about 100,000 balance springs were made in a special vacuum furnace but only a few thousand were usable, and those could only be found by test running them in a working movement, causing assembly costs to skyrocket. In 1993, after making about 2700 of them IWC discontinued production. The use of non-magnetic materials was clearly theoretically superior to shielding materials, but it was an idea whose time had not yet come.
Interestingly, niobium-zirconium is also the material Rolex uses for its Parachrom Blu balance spring. The new version of the Milgauss (introduced in 2007) which something of a hybrid –while the Milgauss uses an inner case of ferromagnetic material to protect the movement, it also uses an amagnetic Parachrom Blu balance spring, and the escape wheel (normally made of steel) is made of amagnetic nickel-phosphorus.
Why go the extra mile? Magnetism can certainly adversely affect a watch by affecting its ferromagnetic components, but it can also cumulatively and irreversibly change the temperature compensation properties of balance springs made of Nivarox-type alloys. Using an amagnetic material prevents these cumulative effects from occurring –a very relevant concern in a modern world full of powerful permanent magnets, and electric currents in motors and wiring which generate strong fields from current flow.
The most successful anti-magnetic watch in history, however, now looks to be Omega’s Anti-Magnetic Aqua Terra 15,000 gauss (equal to 1.2 million A/m.) At the official introduction of the watch, CEO Stephen Urquhart and his team explained that for them, half the battle to create the world’s most anti-magnetic watch was half won already by the introduction to Omega’s new movements of silicon as a balance spring material –silicon is completely unaffected by magnetic fields. Silicon, a metalloid, is an ideal material for an anti-magnetic watch, and other innovations were made as well –for instance, the lever, escape wheel, balance, and balance screws are all made of amagnetic materials (the escape wheel is of a nickel phosphorus alloy, for instance.)
Omega, says Urquhart, expects to be able to industrialize the technology in the Aqua Terra >15,000 gauss successfully; the watch will be released –with its distinctive black and yellow seconds hand –in October, and, perhaps most significantly, Omega intends to transition its entire movement production to this level of anti-magnetic technology by 2017. In addition to offering unprecedented resistance to magnetism, the fact that the watch does not rely on a ferromagnetic inner case means that it can be fitted with a display back, and that additional openings in the dial –for a date display, for instance –are no longer a problem.
IWC’s Ingenieur 500,000 A/m was, by the way, resistant to fields much more powerful than the number in the name of the watch. In 1989, then-IWC managing director Günter Blümlein placed one in an MRI machine and subjected it to a field strength of 3.7 million A/m –the watch was totally unaffected. (More details on this intriguing watch can be found in this article by Alexander Linz.) Omega, we can’t help note, has named their watch the Aqua Terra > (greater than) 15,000 gauss –according to CEO Stephen Urquhart, that number represents the maximum strength their test apparatus can generate, but it seems from the name that even greater performance could be expected. The enormous dipole magnets (made of niobium/titanium) used at the Large Hadron Collider, for instance, generate a field of 8.33 tesla, or about 6,629,00 A/m.
Next stop, LHC?