How Apple Made Its Jet Black iPhone None More Black

We spoke with experts to learn how Apple's anodization process works---and what sets its method apart.
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Apple

Since day one, the iPhone has come in various shades of black. (If you're the kind of person who calls "Space Grey" black.) But now it comes in an even deeper, darker, richer shade of black.

Apple calls that shade Jet Black. We call it Batmobile black. Anish Kapoor black. None more black. Whatever you call it, the glassy, murdered-out colorway is hands down the most eye-catching feature of the new, souped-up iPhone 7. In one of his signature process videos, chief design officer Jony Ive said Wednesday that Apple developed a whole new nine-step process to achieve the Jet Black iPhone 7's high-gloss finish. That's par for the course with Apple. The company's manufacturing processes rely on no shortage of proprietary technologies, and finishing---the stage at which a product is polished up, literally and figuratively---is certainly one of them. “Apple is doing extraordinary things, finishing-wise,” says engineer Ted Mooney, president of the website finishing.com. “When they claim it is exceptional, it really is.”

But Apple didn’t invent high gloss finishing. So we spoke with Mooney and a couple other experts to learn about key steps in the process---and what sets Apple's manufacturing method apart.

The first thing you need to create a high gloss finish is a perfectly smooth piece of aluminum. Apple smooths the iPhone's casing with something Ive calls "rotational 3-D polishing." Another word for this is buffing. Most manufacturers do this with a chemical wash or electrochemical polishing, but Apple's process is different. “This is a first time ever new method of polishing," says Robert Probert, author of Aluminum How To: The Chromatizing, Anodizing, Hard Coating Handbook. Where a typical manufacturing process might see polishing compounds applied to the phone casing by a rotating buffer wheel, Apple appears to have combined those compounds with the powdery media seen here. "Instead of tumbling or wheel-rubbing," Probert says, "Apple is wiping the parts through this powdery media."

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In Ive's process video, the rig you see here drags and spins multiple iPhone cases through a powder-like compound. The point of this process is to reduce any imperfections in the metal, and prep the case for the anodization process.

Two important things happen during the anodization step, seen here:

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First, gadgets descend into an anodization tank. The tank is full of liquid, and the manufacturer applies electricity to it. This converts the surface of the aluminum into aluminum oxide.__ __(The latter is a chemical compound of aluminum and oxygen that's a lot harder than the former, and more resistant to corrosion.) Second, it makes the aluminum oxide surface porous. That might sound like a step backwards from the polishing stage---it's not. “The pores you’re putting in there are really microscopic, there’s billions and billions,” Mooney says. “You’re not hurting your polishing by doing that.”

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This newly porous surface is like a sponge designed to soak up dye. This is what Ive means when he says “a single component dye is absorbed through a capillary effect to ensure maximum saturation, while becoming part of the surface itself.” Mooney says this step is essential to understanding how the process achieves such a deep and lustrous shade of black. The dye Ive is referring to doesn’t just coat the iPhone case; the porous aluminum actually sops it up.

An ultrafine particle bath comes last, and gives the phone's casing a little extra polish. Mooney says this is the step that really sets Apple apart; it's a level of attention that manufacturers rarely pay other anodized, high-gloss products, like an archer's bow, or knitting needles. But then, those aren’t devices you reach for hundreds of times a day, either.

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For all the chemistry involved, this finishing process happens in under an hour. “I just wrote specifications for a shop to do anodizing for airplane parts,” Probert says. “Every 40 minutes we get pieces out of the anodization tank. It’s a 10,000 gallon tank. So you can imagine how many little Apple covers we could fit.”

That’s good for Apple. As of July, the company had sold more than a billion iPhones. With that kind of consumer love, they’ll need to keep making them fast---even the fancy, Jet Black ones.