"Invisible ink" features found in Basquiat painting

Art conservator Emily Macdonald-Korth was evaluationg a client's Jean-Michel Basquiat untitled painting from 1981 when she looked at the work under ultraviolet light to reveal any repairs or varnishing. From artnet News:

"I start looking at this thing and I see these arrows," Macdonald-Korth told artnet News. She flipped the lights back on to make sure she wasn't imagining things and the arrows disappeared. She flipped the lights off again and there they were: two arrows drawn in what looked like black-light crayon, virtually identical to other arrows drawn visibly on the canvas with red and black oil sticks. "I've never seen anything like it," she said. "He basically did a totally secret part of this painting."

In fact, this isn't the first time Basquiat has been known to use fluorescent UV materials. In 2012, Sotheby's London discovered that his painting Orange Sports Figure from 1982-done just months after the one Macdonald-Korth analyzed-contained an invisible-ink signature of the artist's name in the bottom right corner. But he has never been known to include UV-specific imagery in his work.