The six cool, abstract 9 and a half feet square paintings regularly spaced around the walls of this white room were made by Gerhard Richter in 2006 as a coherent group. All six are multi-coloured, but two are predominantly grey, two grey and green, one grey and red - and one grey, yellow and white. Horizontal and vertical textures in the blurred colours where the thick paint has been dragged across and down the canvas suggest reflections in the surface of a river – particularly where there are deep greens.

Close to, areas of both smooth and pitted paint reveal that the works have been built up in successive layers. The deeper the ‘pit’ the greater the variety of contrasting colours. After application each layer has then been scraped back with a big palette knife - removing some paint completely and smudging the colours left behind. Another layer has then been put on top, scraped back – and so on. So the works have developed in unanticipated ways. They’re a bit like a billboard where, in preparation for a new set of posters being stuck on, the latest have been ripped off - revealing fragments of hundreds of past posters beneath. Richter has said ‘I don’t know what I want; … I like the indefinite, the boundless; I like continual uncertainty’.

Richter called these works ‘Cage paintings’ after the American avant-garde composer John Cage. Cage introduced elements of chance into the creation and performance of his music, and is best known for his pieces for prepared piano – a piano with sound-altering objects placed on the strings – and his composition ‘four minutes 33 seconds’ - performed without a single note being played so that the random sounds of the environment can be heard. Richter shares this interest in what is revealed by absence or removal. The ‘Cage paintings’ have been made as much by destroying as by creating.

The paint here was applied with a large squeegee brush - so there are none of the distinctive expressive marks characteristic of Abstract Expressionism. The surface is scored in places, but these gouges too have an anonymous feel. Richter’s concern is always with the image itself – rather than direct references to anything else – and with the continuous process of questioning.