In 1981, I think, for the Kunsthalle in Düsseldorf. Before that I designed a mirror room for Kasper König's Westkunst show, but it was never built. All that exists is the design - four mirrors for one room.

It is a danger to wait around for an idea to occur to you. You have to find the idea.

When I look back on the townscapes now, they do seem to me to recall certain images of the destruction of Dresden during the war.

It was not possible for us to produce the same optimism and the same kind of humour or irony. Actually, it was not irony. Lichtenstein is not ironic but he does have a special kind of humour. That's how I could describe it: humour and optimism. For Polke and me, everything was more fragmented. But how it was broken up is hard to describe.

I was a student, and as such you generally rely on prior models of how to make art, but these were not satisfying. Then I discovered in photos what had been missing in paintings; namely that they make a terrific variety of statements and have great substance. That is what I wanted to convey to paintings and apply to it.

Above all, it's never blind chance: it's a chance that is always planned, but also always surprising. And I need it in order to carry on, in order to eradicate my mistakes, to destroy what I've worked out wrong, to introduce something different and disruptive. I'm often astonished to find how much better chance is than I am.

Art should be serious, not a joke. I dont like to laugh about art.