It was chiefly through his paintings that Co Westerik made his name. His output is small, just three or four a year. He bases his paintings on a preliminary ‘idea sketch’: small drawings – some measuring just a few centimetres – in which he sets down flashes of inspiration and situations with the potential to become a painting. Having chosen one of these sketches, Westerik begins by deciding the dimensions before precisely transferring the enlarged idea sketch to his canvas or panel. He then applies the imprimatura or underpainting in tempera, over which he paints in oils and/or alkyds.