What Is the Apple Watch’s New iGold? Metallurgists Speak Out

It is not surprising that Apple showered the 18k gold it’s using for its high-end watch with superlatives. It claims its alloy is “twice as hard as standard gold”—which would be about 400 vickers, depending on your definition of “standard gold”—as well as “elegant,” “beautiful,” and “uncompromisingly durable.”

So what is this widely hailed—by Apple, at least—iGold? The company did not respond to a request for comment to JCK, but some clues have appeared in the media:

– First, Jonathan Ive, Apple senior vice president of design, told The Financial Times the metal’s hardness stems from its molecules being closer together.

– Second, there is this Ive-narrated promotional video, part of a series a Bloomberg writer called “metallurgy porn.” (Surely the first time those two words have gone together.)

– Third, there is this widely cited patent granted to Apple last December for a “gold matrix metal composite,” which involves blending gold powder with ceramic powder.

– Fourth, there is this patent application—summarized here by Patently Apple—which was just published yesterday.

JCK ran all this by leading metallurgists.

First, no one took the “molecules closer together” comment seriously. “This will get any metallurgist’s blood boiling,” says Joseph Strauss, president of Queensbury, N.Y.-based equipment manufacturer HJE, which specializes in precious metal powder metallurgy. “Atomic forces are very strong, and there is nothing one can do to push them closer and keep them close.”

Adds Stewart Grice, mill director of Hoover & Strong, a manufacturer of findings and recycled metals: “Solids and liquids are incompressible. If liquids weren’t incompressible, then your hydraulic brakes on your car wouldn’t work.”

As far as the video, it shows a “typical, but anal-retentive, method of making watch case blanks,” Strauss says.

And while the December patent for the metal-ceramic composite material has been spotlighted in countless articles, it’s highly unlikely it’s the same process described in the video, says Shan Aithal, corporate metallurgist for jewelry manufacturer Stuller.

The described composite would be brittle, less dense than standard gold, and have a heft like brass, says Aithal. The brittleness means that the gold couldn’t be flattened by rolling, as shown in the video. He notes that watchmaker Hublot also introduced a ceramic-gold mixture in 2011.

(When asked about Apple’s patent, Hublot spokeswoman Anaïs Tréand calls the brand’s new Magic Gold “unique,” noting it is unscratchable, with a hardness approaching 1,000 vickers—more than double what Apple claims for its gold. Apple, we should note, never bills the gold as scratch-resistant in its marketing, though that anonymously sourced claim did appear in The Wall Street Journal.)

While we don’t know if Apple will ever use the composite, many commenters have pointed out that the process would allow it to use less gold in the watch.

“Most ceramics, being far less dense than gold, greatly increase the volume of the 18k composite over a conventional 18k gold alloy,” says Strauss. So if Apple uses the described composite material, “the same size of watch case … will contain less gold than [one produced with] a conventional 18k gold alloy.”

Any gold-ceramic composite would melt down differently than normal 18k gold, Aithal says.

“You can’t remelt and reclaim the gold,” he says. “You would have to send it to a refiner. In normal 18k gold, whatever scrap you generate is true to the original formula. They all mix together. But you when the melt the composite, the ceramic would separate out. It would float up.”

That brings us to the patent application, which does appear to describe what Apple is using. For one, it references an alloy made using copper, palladium, and silver—also mentioned on the video.

It’s also basic metallurgy. “That patent application should, and may, get turned down,” says Strauss. “However, it did impress me in that it was incredibly detailed in the compositions.”

And Grice was struck by some of its claims:

What they seem to have here is that they have worked out, for specific compositions, how to heat treat (solution treat and age) to get increased hardness and tensile properties above what you would normally expect without over-ageing. The process of age hardening is not new and has been around for centuries, but if the data they quote is correct then this is quite nice … 300HV [vickers] for an 18kt yellow alloy containing 13%+ silver and 1% palladium is quite miraculous. The palladium will not do much here as far as I can see and at face value the composition seem unremarkable. What is remarkable is the fact that they can age it at 300 degrees Celsius for 8 hours, keep a 40 micron grain size (there are no grain refiners included in alloy 1 according to the data) and get 312HV. Also 900 MPa for tensile strength is also about double what you would expect for this composition.

Still, he thinks there is “something missing” in the patent that would complete the picture.

So from what we have seen, Apple seems to have refined—to use an appropriate word—techniques already out there, with one possibly impressive advance, a few new twists, and a lot of hype. All very Apple.

“If they’ve managed to get these results from these alloys, then good luck to them,” says Grice. “They are not claiming ‘tighter molecules’ or any other such rubbish. If it all is actually true, then we may just have a case of good science.”

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JCK News Director

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