Modern British art has a reputation for press-baiting controversy and often comical perversity. But in their own quiet, unflashy way, Andy Goldsworthy's site-specific "earthworks" are every bit as radical as Damien Hirst's sharks or Tracy Emin's bed.

This softly spoken, fortysomething Scot fashions mutable sculptures from wood, ice, leaves and stone that are specifically designed to move, change and erode over time. This beguiling if rather po-faced documentary, a surprise hit in the States, charts his unique working methods and creative processes.

Following Goldsworthy from his 'home base' in Dumfriesshire to Canada and France, director Thomas Reidelsheimer patiently records the painstaking construction of such ephemeral pieces as an igloo made of driftwood, a stone wall laced with wool, and the sculptor's signature "rock cones".

Tension is surprisingly evoked through the necessity to complete these works before they are destroyed by rising tides, strong winds and other natural phenomena, while unintentional humour comes from Goldsworthy's stoical acceptance of hours of toil decimated in an instant.

With his cracked, mucky fingernails and gnomic utterances ("Art for me is a form of nourishment"; "Good art keeps you warm"), Andy cuts an eccentric but likeable figure genuinely at a loss to explain where his inspiration comes from. (His wife's query "So what are you going to make today?" is greeted with befuddled exasperation.)

But Reidelsheimer's film would perhaps have benefited from some external critique of his subject's creations. This lack of context makes for a curiously precious, airless affair - odd considering it was mostly shot outdoors.