Scientists solve mystery of ‘art acne’ on Georgia O’Keeffe’s paintings
February 21, 2019 5:23 PM   Subscribe

O’Keeffe’s “Pedernal, 1941”—a sweeping vista of pinks, greens, and yellows creeping up the canvas to the mountain’s darkened summit—is experiencing a peculiar kind of decay. The artist noticed it herself, remarking on granulations, discoloration, and small spots where the paint disappeared altogether in letters to conservator Caroline Keck in 1947. Known as surface protrusions, or “art acne”, this pimpling afflicts oil paintings from every time and place. But the reasons for O’Keeffe’s deformations, which only grew worse over the decades, remained a mystery. [PopSci]

Short video from Northwestern University describing their conservation efforts in cooperation with the Georgia O’Keeffe Museum [YouTube, 3m09s]

Diagnosing 'art acne' in Georgia O'Keeffe's paintings: Novel hand-held tool detects, maps and monitors destructive pimple-like protrusions in precious works of art [ScienceDaily]
posted by nightrecordings (5 comments total) 13 users marked this as a favorite
I'm glad that science found this issue and that science and chemistry are helping to solve it. It's good that the technology is being applied to many other paintings as well. Good for preservation as a whole.
posted by Fizz at 7:27 PM on February 21, 2019 [1 favorite]

Oh man, that's interesting. I'd like to know a little more about the actual process by which the metal soaps are occurring; it feels like that got sidestepped in the sources in favor of the low-cost imaging bit, but maybe it's been documented previously.

There's a whole pile of weird little chemistry gotchas in the history of oil paints—the Pop Sci article mentions The Secret Lives of Color but I got a lot more out of Philip Ball's fascinating and sometimes salty Bright Earth and highly recommend it if you want to get into the weeds a bit—but it's a bit funny in particular that lead white sounds like the main source of this particular trouble because it is such a stubborn standby for a lot of tradition-minded painters. It's nasty and poisonous and not as bright as Titanium White but it is the classical white paint and has the advantage of hundreds of years of attested usage (and usage in paintings still seen hundreds of years later, which is the ultimate archival pedigree) and so people keep using it anyway even as it gets in some places increasingly inconvenient to legally obtain.

There's a certain amount of concern that contemporary Titanium/Zinc White mixtures won't last well over the long haul (maybe a tendency of the emulsion layer to crack over time depending on the pigments mixed in and the proportion of white to other colors?), so there's an explicit fussy argument in favor of lead instead. But I don't know that there's any specific problems with straight up Titanium White, so much as just a concern that there might be some unlabeled zinc in the mix after all.

Oil paints are a whole lot more complicated than you'd think they should be at face value.
posted by cortex at 10:08 PM on February 21, 2019 [6 favorites]

Metal soap? Metal soap? Metal soap?
posted by clew at 11:36 PM on February 21, 2019 [2 favorites]

Metal soap? Metal soap? Metal soap?

With lead. Heavy metal soap. \m/
posted by otherchaz at 3:45 AM on February 22, 2019 [3 favorites]

Oil paints are a whole lot more complicated than you'd think they should be at face value.

Which is why, early on, I opted to work in acrylics. I just don't have the patience for all that.

It's kind of funny, though. Whenever I go over to the local community gallery, it's always very obvious who's using oils pretty much straight from the tube, and who's delved into the alchemy of oils.
posted by Thorzdad at 4:38 AM on February 22, 2019 [1 favorite]

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