Modern & Abstract: Pure Form and Primary Colour

Somewhere in the first half of the twentieth century the picture stopped pretending to be a window. Kandinsky let colour and circle ring on their own. Mondrian reduced painting to the upright, the level and three primaries. Matisse, too ill to stand at an easel, cut his shapes straight out of painted paper. What is left is form and colour, with nothing behind them — which is exactly what a curved white cup wants.