Sennelier oil pastels use top quality, high covering pigments, an extremely pure synthetic binding medium and mineral wax.

T : Transparent, O : Opaque, 

*** : Very good light-fastness = I ASTM Lightfastness
** : Good light-fastness = II ASTM Lightfastness
* : Average light-fastness = III ASTM Lightfastness

Originally In developed in 1949 by Sennelier for Pablo PICASSO who had been looking for a medium that could be used freely on a variety of surfaces without fading or cracking.

The pigments are ground with an inert, non-drying binding medium that does not oxidise and that has no effect upon either film stability or surface. This base is then mixed with a  neutral pH wax.