Allie Biswas interviews curator Courtney J. Martin about the work of Robert Ryman on the occasion of an exhibition of works by Ryman at Dia:Chelsea, New York, on view through June 18, 2016.

Martin comments: "it was never just white paint: at the very beginning, he was simply experimenting. In many ways, it’s not just the achromatic factor, there is also the question of surface depth. Sometimes he applied paint with a palette knife, resulting in dense, encrusted surfaces. In other works, the paint is sheer and thin, like a wash. Viewers get caught up in looking at the white and yet we're missing what’s really happening. We are missing the application and the method. For many of the works, colour has been applied underneath, and then been painted over with white. When you look at the work chronologically, each painting is a challenge or a question that Ryman answered or complicated with the next painting that he completed."