Rachel Whiteread: ‘I have a clarity I never had before’

The artist has taken a radical new direction, turning her back on casts and creating sculptures from scavenged material. She explains how a bipolar diagnosis has changed her workWhen I last spoke to Rachel Whiteread, I declared loftily that she would always make casts, that she’d never do anything else. Because that’s what she’d been doing for more than 30 years; that was her language. She began by casting the void under a chair, then she cast the gap under a bed. She cast tiny