Opaque watercolour, sometimes also known as body colour. It differs from transparent watercolour in that the pigments are bound with glue and the lighter tones are obtained by the admixture of white pigment. Its degree of opacity varies with the amount of white that is added, but in general it is sufficient to prevent the reflection of the ground through the paint and it therefore lacks the luminosity of transparent watercolour painting. It is, however, easier to use, as trials and errors can be painted over. The colours sold as poster paints by commercial colourmen are usually a form of gouache.