In 1998, almost fifty years after Jackson Pollock painted "One: Number 31," the curators at MoMA realized the painting was looking a little... grimy.

As chief conservator James Coddington explains in a new video, the team at MoMA started wondering if something had gone terribly wrong in the painting's past. Using x-radiography, they were able to analyze the canvas for particularly weird anomalies—and they quickly found that someone had taken a crack at restoring it. A bad one.

The damage wasn’t Ecco Monkey level, but it was bad enough that MoMA decided to try to undo the damage. Removing paint from a multi-million dollar piece of art is no small task; it took the team months to determine exactly which drips and splatters were inauthentic, using ultraviolet light and microscopic paint samples scraped from the canvas to generate a map of what came from Pollock and what didn’t.

There are plenty of art historians out there who will tell you that botched restoration jobs are part of “the life of the painting,” but MoMA doesn’t believe in esoteric crap like that. Instead, they scraped all of the unwanted paint off using q-tips dipped in chemicals that remove only the type of paint the restorer was using, leaving the Pollock untouched.

Because his style is so easily parroted, Pollock’s work has been a great testing ground for new ideas about restoration and authenticity. For example, art authenticators have gone so far as to compare the paint on a canvas with the 60-year-old paint flecks ground into his studio floor; and in 2011, group of Harvard scientists did an in-depth analysis of the physics of his technique, making it easier to calculate whether or not it was actually Pollock that did the paint slingin’. [MoMA]

Restoring a Pollock With X-Rays and Ultraviolet Light