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.

Family photos, pictures of groups, those are truely wonderful. And they are just as good as the old masters, just as rich and just as beautifully composed (what does that mean anyway).

Based on mixtures of the three primary colours, along with black and white, I come up with a certain number of possible colours and, by multiplying these by two or four, I obtain a definite number of colour fields that I multiply yet again by two, etc. But the complete realization of this project demands a great deal of time and work.

Only about one per cent of my paintings show family members. Do they help me deal with problems? It's likely that these problems can only be depicted. But photographs, private ones and others, keep appearing that fascinate me so much that I want to paint them. And sometimes the real meaning these images have for me only becomes apparent later.

It's that same quality I've been talking about. It's neither contrived, nor surprising and smart, not baffling, not witty, not interesting, not cynical, it can't be planned and it probably can't even be described. It's just good.

What attracted me about my mirrors was the idea of having nothing manipulated in them. A piece of bought mirror. Just hung there, without any addition, to operate immediately and directly. Even at the risk of being boring. Mere demonstration. The mirrors, and even more the Panes of Glass, were also certainly directed against Duchamp, against his Large Glass.

When I first painted a number of canvases grey all over (about eight years ago), I did so because I did not know what to paint, or what there might be to paint: so wretched a start could lead to nothing meaningful. As time went on, however, I observed differences of quality among the grey surfaces - and also that these betrayed nothing of the destructive motivation that lay behind them. The pictures began to teach me. By generalizing a personal dilemma, they resolved it.