Oil pastels are rectangular, similar in size to crayons. They come in all different pigments, which are often available in sets of all the basic pigments to advanced sets with lots of pigment choices. Oil pastels are sometimes called hard pastels. They are good for precision because of their hard oil-based consistency.
Oil pastel starts with the finely ground-up pigment. These are then mixed with either inert oil or wax. Being acid free, they do not harden or crack. The result is an oily or waxy medium that is fairly easy to use, but not easy to erase because it sticks to the surface.
Oil pastels were created in the Taisho period of Japan (1910 to 1920) with the help of the artist Kanae Yamamoto, by two private school owners, Rinzo Satake and Shoukou Sasaki. What they came up with was a cross between a crayon and soft or dry pastel. Their company was named Sakura Crayon Co. This was considered the ideal material to teach children to be creative by creating free form art. In 1947, artists Henri Goetz and Pablo Picasso requested a more professional version of the original. Henri Sennelier created this product, and the Sennelier brand is still one of the most popular oil pastel brands today.
It is easier to move soft pastel on a surface since it has much less of a binder than oil pastels. After a piece is created in soft pastels, a fixative needs to be applied. Oil pastels have more of an oil paint consistency, but are harder, like crayon. They are more difficult to blend than the soft pastels, but do not require a fixative. With practice, blending oil pastel colors can become easier, as there is more control with the medium.
Oil pastels can be used on many different surfaces such as paper, illustration board, canvas and wood. Experimenting with surfaces can be quite interesting with oil pastels. Because of its durable nature, it is not easily washed or smudged off. Many interesting art pieces can be created that might not be possible with other media.