From the manufacturer:
Created in the 1940's in collaboration with Pablo Picasso these creamy, lipstick-like pastels are rich in pigment, cover well, and have outstanding opacity and lightfastness. They may be thinned with turpentine and worked with a brush, are acid-free and can be applied to any surface. They are made with top quality pigments, an extremely pure synthetic binding medium and mineral wax. The pigments are ground with an inert, non-siccative binding medium that does not oxidize, ensuring stability of film and surface. The balance of this mix results in a creamy texture that invites broad strokes and freedom of expression. The high pigment content results in high coloring and covering potential and excellent brightness. These sticks come in regular and "Grand", which is the equivalent of eight regular size sticks, measuring .75" by 5".