LONDON - Sotheby's says it has discovered that grafitti artist Jean-Michel Basquiat secretly signed one of his paintings in invisible ink.
The auction house is selling "Orange Sports Figure," estimated to be worth between 3 million pounds and 4 million pounds ($4.7 million and $6.3 million).
Basquiat, who became a New York art star, signed relatively few of his canvases. But Sotheby's said ultraviolet light revealed the artist's name and the date 1982 beneath the layers of paint.
Cheyenne Westphal, head of contemporary art at Sotheby's Europe, said Tuesday that "nobody else probably ever knew about this invisible inscription" -- and there could be more on other canvasses.
Basquiat died of a drug overdose in 1988, at age 27. The painting is for sale in London Wednesday.
