The painting ‘verdichtung zu caput mortuum’ (distillation to caput mortuum) is one of a series of variations, with different expressive qualities deriving from the combination of colours used in each. The series was started in 1964. All the pictures are placed on the diagonal – Bill sometimes called them “pointed pictures”.

In ‘verdichtung zu caput mortuum’ the area in the centre is coloured a dull reddish-brown, or caput mortuum – the term applied to a residue after distillation or sublimation in alchemy. Here it acquires a special quality from the external isosceles triangles and bands of colour, and becomes a surface against which the yellow-red and bluish-purple colour chords can resonate as they interact with the reddish-brown.

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