painting

Application of coloured pigment to a surface. The chief methods of painting are: tempera emulsion painting, with a gelatinous (for example, egg yolk) rather than oil base – known in ancient Egypt; fresco watercolour painting on plaster walls – the palace of Knossos, Crete, contains examples from about 2000 BC; ink developed in China for calligraphy in the Sung period and highly popular in Japan from the 15th century; oil ground pigments in linseed, walnut, or other oil, it spread from northern to southern Europe in the 15th century; watercolour pigments combined with gum arabic and glycerol, which are diluted with water – the method was developed in the 15th–17th centuries for wash drawings; acrylic synthetic pigments developed after World War II, the colours are very hard and brilliant.

High-resolution video cameras and computers are now being used to help art experts identify damage to paintings in some of the world's major galleries, including the Louvre, France, and the National Gallery, UK. The system identifies damage by comparing ‘before’ and ‘after’ images in order to highlight changes in the craquelure.