Chuck Close Prints: Process and Collaboration, White Cube Bermondsey, London

Chuck Close suffered a spinal aneuryism in 1988, and the story of the making of his large-scale, painted portraits, works often composed of lozenges of colour organised inside grid-like patterns which cohere visually the further you recede from them, often goes hand in hand with a general acknowledgement of his tremendous battle against physical adversity. He's the man who is forever fighting to make it new from the maddening confines of a wheelchair.

But there is more, much more than all those paintings. This huge touring survey of forty years of his graphic oeuvre (it's been on the road in America for almost a decade), one hundred and fifty works in all, and spanning four decades, shows us a dimension to his work hitherto little known, and it is in many respects the more interesting part because it allows us to enter into how he thinks. He is always trying something new – a new technique, a special kind of rag paper. Each print process offers different kinds of possibilities. Even some of his accidents come good in the end – look at the series of silkscreen prints on Mylar of the painter Alex Katz, for example, in that strange range of greys. They possess the uncanny sheen of metal. This is a kind of laboratory of ceaseless experimentation. How does one make a human identity? What can a mezzotint do that a lithograph can't?

Close likes to be very, very close to his subjects. He likes to close off, isolate an image in order to rudely interrogate the lineaments of the human face. It's a bit like a police line up or a photo booth. That stark, that pitiless. For all that, his subjects are usually friends, family, artists, the famous and the unfamous – and, oh yes, himself. Even though he rather dislikes his own appearance, he has consistently been his own most doggedly favourite subject. Philip Glass, that decades-old friend is another regular. When Close first captured Glass decades ago, he was a friend-cum-studio assistant, and down the years Close has never been able to get enough of interrogating that face, with its pulpy hanging mouth, its wayward eyes (that could quite easily have belonged to two entirely separate people), and all topped by that unruly, Medusa-like shock of hair. Or look at what Close makes of the Greek-American painter Lucas Samarras, with his ferociously intent stare. Close has his face spin about that stare in a frantic catherine-wheel whirl of colour. There's nothing quite so inexhaustible as the compulsion to look.

To look at some of Chuck Close's prints on show click here or on "view gallery".