Speaking purely for myself, I can say that it was my very acute feeling for the matière, for the substance of painting, which pushed me into thinking about the possibilities of the medium. I wanted to create a kind of substance by means of brush-work. But that is the kind of discovery which one makes gradually, though once a beginning had been made other discoveries follow. Thus it was that I subsequently began to introduce sand, sawdust and metal filings into my pictures. For I suddenly saw the extent to which colour is related to the substance.. .So my great delight was the 'material' character which I could give to my pictures by introducing these extraneous elements. In short, they provided me with a means of getting further away from idealism in 'representing' the things with which I was concerned.