You can achieve sharp, definitive points by breaking or by sharpening with a blade. Hard pastels are used mainly either in the preliminary stage of a painting, or in the final, touch-up stages. Hard pastel doesn't clog the tooth of the paper as readily. They are excellent for cross-hatching and feathering. Pastel pencils also allow greater control and ease in handling.
Soft pastels have minimal binding agents and contain proportionately more pigment than hard pastels.
Their colors are mixed with white chalk, clay, gypsum, or a dark substance such as charcoal to increase the covering power of the pigments. The white filler is responsible for the delicacy of hue associated with light colors such as flesh tints. Darker fillers create rich earth tones and deeper hues of colors. They can be worked and blended into thick, velvety finishes, covering large areas very quickly. As a result, however, soft pastels disappear rapidly.