I have always enjoyed working with chalk pastel. It is the only medium that doesn't have a medium. Paint is just pigment that is ground in a
medium to bind it together and dry to a film-like surface. The oil in oil paints has a yellow cast that only darkens with age, and any pigment
when ground into a liquid medium changes it's tonal colour quite radically. Chalk pastel is simply the natural pigment held to together with a
little gum arabic to make a stick-like crayon . Of course it is very fragile and needs protecting under glass, but the purity of tones you can achieve -
especially the blues - is unsurpassed.