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Copies of Copies: The Surprisingly Complicated Process of Making a CD

It takes a whole lot of steps to get an optical disc ready for your CD Walkman—yet it has a surprising amount in common with pressing a record.

Re-Exposure is an occasional Motherboard feature where we look back on delightful old tech photos from wire service archives.

At one time, compact discs were made by the hundreds of millions each year. At the music industry's peak in 2000, 785 million units were sold in a single year, which is especially impressive when all the units were physical, mostly in CD form.

Other forms of discs were huge around this time as well. The Sony Playstation was the first truly successful disc-based console, and the DVD industry was starting to come on strong. (There were also plenty of embarrassing experiments, though, like DIVX.)

And of course, you can't sell hundreds of millions of pieces of aluminum-covered polycarbonate if you don't have factories that can keep up with the demand. The above shot shows a man in a German factory analyzing non-coated discs during that particularly heady time for the music industry, in May 2001. The rise of Napster, Gnutella, and other file-sharing services had put the fear of God into tunesmiths, but when it comes down to it, the party was still going strong around this time.

People on those services were downloading copies of copies, and in many ways, that what CD factories do—they print copies of copies of music onto those physical mediums. A YouTube clip of a 1995 factory tour of a Disc Manufacturing, Inc., facility in Anaheim, California, breaks down the printing process. It actually has a lot in common with a vinyl record: with the information placed in a spiral groove, but the scale way smaller.

"If a single pit on a CD was blown up to the size of a grain of rice, the CD it would be on would be over a mile and a half across," the clip helpfully explains.

Built from the base of a glass master disc, a compact disc is built from millions of these tiny pits, placed onto the base by a laser. The glass master is then coated with silver, which is then used to create a series of pristine copies of the microscopic pits, with later generations created from nickel. (This process makes it so that if, say, you're making an Adele record, you can press records it from numerous copies of the master.)

From these later generations, molds are created for printing polycarbonate discs. Afterwards, a layer of aluminum is put on top, to reflect the pits back to the laser. (This explains why, as I noted last month, it's worse to scratch a disc on the top than the bottom.)

Unlike a vinyl record-production facility, the work all takes place in clean rooms, driven by a combination of human testing and robotics.

All in all, it's a surprisingly clinical process to get a Train CD out of the factory.