Will Shank, conservator at the National Gallery of Art in Washington DC, always suspected something was buried beneath Picasso’s Scène de Rue, a somber street scene painted by Picasso in the fall of 1900 during his first stay in Paris. Unusual brushwork patterns and colors peeking through cracks in the surface of the painting fueled the suspicion that another image lay underneath. X-rays revealed a second painting: a French nightclub scene of patrons and can-can dancers which appeared to be the prototype for Picasso’s Le Moulin de la Galette, a 1900 painting thought to be the first Picasso made in Paris. Technicians extracted the colors visible through the cracks in the surface of Scène de Rue and with the help of digital-imaging techniques transferred them onto a black-and-white radiograph (see image above).
San Francisco Museum of Modern Art has a page dedicated to topic, with historical background information on Picasso in the Paris of the early 1900s as well as and a nice little flash demo showing the revealing of the ‘Hiden Picasso’.