Alla prima means that the painting is painted 'wet-on-wet'. In this technique, the colours are mixed not only on the palette but also on the painting itself. Painting will therefore have to be done quickly; no colour should dry in before the painting is completed. With this technique the paint can be thinned with the same thinner each time, or the paint can be used pure. If diluent is used, a good painting medium will achieve the most durable result.