Caro's sculpture looked outward and inward

Some artists throughout their careers pursue what amounts to a single basic idea, developing and consolidating it. Others, like British sculptor Anthony Caro, persistently reinvent their art while remaining true to themselves.

A retrospective at Tate Britain covering Caro's work from 1951 to 2004 shows how impossible it would have been to predict the different expressive, contradictory possibilities he has explored. It is almost as though he has deliberately surprised himself by deciding to investigate the opposite of what he has already done.

Looking at "Orangerie," a welded steel and painted sculpture from the late '60s in which weight appears to be defied by an energized, almost playful lightness, is a radically different experience from seeing the undisguised weightiness of sculptures Caro made only a few years later.

"Orangerie" was one of several works that marked the culmination of a period in which he literally opened up his sculpture to light and air, and emphasized line and edge. Most of his '60s sculpture stands directly on the ground rather than on a base. It is horizontal in orientation rather than traditionally vertical. His forms and shapes travel over the ground rather than obviously skyward. They touch the ground at several points, avoiding concentration on a single support.

At this period, Caro aimed to make his sculpture as abstract as possible. Relating it to music, writing, or dance, he gave it a spatial narrative. One part of such a Caro sculpture leads to another like a chain of events. As Caro followed these ideas, his works no longer had an inner core hidden within an opaque form. Their spaces became as unhidden as possible. Yet as the exhibition shows, Caro seems to have come to think that such lightness might also be too facile - not felt deeply enough. Much of his subsequent work has been more heavyweight, often inward-looking, and even shadowy and secretive.

• The Caro exhibition is on view at Tate Britain through April 17.