I first came up with the idea for the colour-chart pictures back in 1966, and my preoccupation with the topic culminated in 1974 with a painting that consisted of 4,096 colour fields. Initially I was attracted by the typical Pop Art aestheticism of using standard colour-sample cards; I preferred the unartistic, tasteful and secular illustration of the different tones to the paintings of Albers, Bill, Calderara, Lohse, etc.

I remember that I felt I had to avoid all these sensational photos, the hanged woman, the man who shot himself, and so forth. I collected a great deal of material, including a number of banal, irrelevant photos, and then in the course of my work I came back to the very pictures I had actually wanted to avoid, which summed up the various stories.

A work of art is itself an object, first of all, and so manipulation is unavoidable: it's a prerequisite. But I needed the greater objectivity of the photograph in order to correct my own way of seeing: for instance, if I draw an object from nature, I start to stylize and to change it in accordance with my personal vision and my training. But if I paint from a photograph, I can forget all the criteria that I get from these sources. I can paint against my will, as it were. And that, to me, felt like an enrichment.

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.

Art is the pure realization of religious feeling, capacity for faith, longing for God. ... The ability to believe is our outstanding quality, and only art adequately translates it into reality. But when we assuage our need for faith with an ideology we court disaster.

And then the work bears a strong sense of leave-taking for me personally. It ends the work I began in the 1960s (paintings from black-and-white photographs), with a compressed summation that precludes any possible continuation. And so it is a leave-taking from thoughts and feelings of my own on a very basic level. Not that this is a deliberate act, of course; it is a quasi-automatic sequence of disintegration and reformation which I can perceive, as always, only in retrospect.

I began in 1976, with small abstract paintings that allowed me to do what I had never let myself do: put something down at random. And then, of course, I realized that it never can be random. It was all a way of opening a door for me. If I don't know what's coming - that is, if I have no hard-and-fast image, as I have with a photographic original - then arbitrary choice and chance play an important part.