Pastel is an art medium in the form of a stick, consisting of pure powdered pigment and a binder. The pigments used in pastels are the same as those used to produce all coloured art media, including oil paints; the binder is of a neutral hue and low saturation.
The colour effect of pastels is closer to the natural dry pigments than that of any other process. Pastel sticks or crayons consist of pure powdered pigment combined with a binder. The exact composition and characteristics of an individual pastel stick depends on the type of pastel and the type and amount of binder used. It also varies by individual manufacturer.
Dry pastels have historically used binders such as gum arabic and gum tragacanth. Methyl cellulose was introduced as a binder in the twentieth century. Often a chalk or gypsum component is present. They are available in varying degrees of hardness, the softer varieties being wrapped in paper.
Dry pastel media can be subdivided as follows:
Soft pastels: This is the most widely used form of pastel. The sticks have a higher portion of pigment and less binder, resulting in brighter colors. The drawing can be readily smudged and blended, but it results in a higher proportion of dust. Finished drawings made with soft pastels require protecting, either framing under glass or spraying with a fixative to prevent smudging.
Hard pastels: These have a higher portion of binder and less pigment, producing a sharp drawing material that is useful for fine details. These can be used with other pastels for drawing outlines and adding accents. However the colors are less brilliant than with soft pastels.
Pastel pencils: These are pencils with a pastel lead. They are useful for adding fine details.
Oil pastels: These have a soft, buttery consistency and intense colors. They are slightly more difficult to blend than soft pastels, but do not require a fixative.
Water-soluble pastels: These are similar to soft pastels, but contain a water-soluble component, such as glycol. This allows the colors to be thinned out using a water wash.