Vocab Lesson: Vapour-Metallised Plastic

A piece of plastic goes in, a piece of metal comes out. At least, that's what vapour metallising seems to accomplish, at least to our immediate senses. It's gilding, except it's been updated for the electronics age. And it's everywhere.

Vapour metallisation is a solution to a common industrial problem: Plastic is easily mouldable, lightweight and above all, cheap to make. On the other hand, "nice" metals are tougher to work with, and more expensive. So, for the same reasons ancient Greek artisans pressed thin layers of gold leaf to statues, countless factories around the world use vapour metallisation treatments to turn plastic into, well, not-plastic. They metallise your laptops and your phones, your mirrors and your car bumpers. You can take it either as a clever manufacturing tool or a terrible mass fraud, a cynical technique to make customers pay for The Metal Lifestyle, only to live with plastic. Your choice! Either way, here's how it works.

What it Means: From Materials and Design: The Art and Science of Material Selection in Product Design: A process in which a thin coating of metal - usually aluminium - is deposited from a vapour onto a component. The vapour is created in a vacuum chamber by direct heating or electron beam heating of the metal, from which is condenses onto the cold component. (Note: The process is often called Physical vapour deposition.)

What THAT Means: Ignoring the hard science of vapour metallisation for a minute, here's what happening, basically: Hunks of plastic, or unfinished metal, are marched into large machines called vacuum metallisers, or liquid metallisers, or sometimes sputtering systems. These can look something like '50s vintage iron lungs, built around large, sturdy-looking tanks and festooned with all manner of tubes and wires, or in more modern incarnations, featureless, room-sized boxes.

The inside of the vacuum metalliser is a bit like a sauna, with industrial components in place of paunchy, leering old men. And rather than humidifying the air with occasional puffs of steam, liquid metallisers vaporise bits of metal into an ultrafine mist. Where sauna-goers strut from behind the curtain glistening under a thin coat of water, vapour-metallised plastics emerge coated with an extremely fine, even layer of real, actual metal. Here's what the whole process looks like, from the outside. (Those are headlight mirrors, by the way):

Of course, vaporising aluminium isn't as easy a ladling water onto a bed of semi-decorative rocks, and what's going on inside this giant mystery box is quite a bit more complicated. And the steam analogy doesn't hold for very long: the steam in a sauna in comprised of molecules of water, floating through an atmosphere filled with various gases. In a metal vaporisers, the vapour is made purely from atoms of the vaporised material, heated either atop a ceramic plate (because metal heaters could produce small amounts of vapour of their own) or by means of a freakin' cathode ray, and spewed into total vacuum. (All the gasses in the air we breath would interfere with all the aluminium atoms floating around.)

This is the reason vapour metal treatments are so desirable: the film they create, though it can be as thin as a few microns, is deposited on the target surface atom by atom, which gives it an atomically (literally!) smooth finish.

Of course, this means that fresh out of the vaporiser, treated plastics are hideously shiny. This makes the technique perfect for turning plastics into mirrors, or creating low-cost chrome-style highlights. But since they're now covered in a superthin film of actual metal, they can be buffed, sanded or blasted into a less offensive sheen. It can be tasteful or tasteless, sort of like spray tanning. Actually, let's go with that: vapour-metallisation is spray tanning, for stuff.

This has been Vocab Lesson, Gizmodo's weekly column on words - the ones you've heard, but can't quite define, or the ones you haven't, but might like to hear about.

If you'd like to hear more about a strange tech word or phrase, send a request along. We'll look it up for you! Probably.

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