Created in the 1940 s in collaboration with 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. Modern Sennelier Oil Pastels have 20 large diameter than the original stick and are available in a larger size called Grand, which is the equivalent of 8 regular size sticks.