A visitor inpsects the puppet for "Yoda" at the Brooklyn Museum of Art in 2002.Chip East / Reuters

There are thousands of recordings in the Star Wars audio archive, which contains the sounds recorded for and used in the films. The franchise’s collection includes the cranking of antique air sirens, the roar of propeller planes, and the industrial rattle of metal stamps on an assembly line.

There are the sounds that make up Chewbacca’s throaty cry, recorded with the help of four bears, a lion, a seal, a badger, and a walrus; and the hum of the lightsaber, based on the mechanical harmony produced by dual motors in an old projector.

It’s been nearly 40 years since the first Star Wars film was released, and the audio archive is showing its age. One of the ways that magnetic tape deteriorates over time is called “sticky-shed syndrome,” or “sticktion,” and it happens when the glue that once held magnetic particles in place comes undone. Tapes end up leaving residue on playing equipment, and making a screeching or distorted noise instead of playing normally.

Sticktion poses a problem for the Star Wars sound engineers who like to dip into the original collection, reviewing and digitizing ancient tape for newer films. Among those engineers is Ben Burtt, whose colleagues call him the Godfather of the Star Wars sounds universe, and who refers to himself a living database of sound.

Burtt and his colleagues rely on a common, but still dicey, solution: They add heat, warming up old reels by putting them in an oven as a way to reactivate magnetic bindings and reduce moisture so they'll play again. And it works! Sometimes.

“You have to learn to bake them correctly,” Burtt said in a Star Wars video extra, holding up a partially melted reel. “If they're left in too long, you end up with this interesting piece of art which used to be sound.”

Even when done correctly, baking magnetic tape at low temperatures reduces the quality of sound over time—meaning it’s a quick fix, but just a temporary one.

The archive isn’t the only place where heat is used for preservation. The British Museum and other institutions, for instance, use a process that involves extreme heat and desalination to conserve Cuneiform Tablets, some of the earliest systems of writing. This method requires baking the tablets at more than 1,300 degrees Fahrenheit, nearly 10 times as hot as an oven that’d be used for reviving magnetic tape.

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