While chalks often come in pastel hues, not all pastels are chalks.
Today's artist can choose between a wide variety of relatively cheap and convenient materials. The advent of synthetic colors and artificial binders expanded the tools available to include pigment sticks, such as chalks and pastels. Different varieties of pastel contain different materials, which affect the drawing experience and the look of the final picture.
Chalk
Chalk is a calcium-heavy rock produced by the underwater deposits of small saltwater organisms. Natural chalk is usually white, although it may also be colored gray or red by mineral or iron deposits. As a drawing implement, chalk is hard and powdery, suitable for quick sketching on dark paper.
Chalk, or synthetic materials that mimic the properties of chalk, is an important ingredient in several other drawing implements, including hard and soft pastels. Pastels are more common for art projects than standard chalk, which is more suitable for chalkboards and sidewalks.
Hard Pastels
Hard pastels are drawing sticks made of pigment, water and chalk. The whiteness of chalk washes out the pigments, making the colors appear pale. Hard pastels create sharp, bright lines on light and dark papers. Some hard pastels can be sharpened, although they can't hold a fine point like a pencil. Pictures produced with hard pastels resemble soft pencil or charcoal drawings in consistency and appearance.
Soft Pastels
Soft pastels are also composed of pigment, water and a smaller amount of chalk or artificial binder. The soft, malleable texture of these pastels creates smooth, smudgy lines that are easily blended on the canvas. Soft pastels cannot be mixed on a palette, so many artists maintain an extensive array of colors to find just the right hue. Pictures made with soft pastels are sometimes called pastel paintings instead of pastel drawings.
Oil Pastels
Some pastels are designed to mimic the appearance and texture of oil paints, rather than dry drawing substances like chalks. These pastels use wet binders, such as oils and waxes, to collect the pigment into a solid stick. Oil-based colors are generally more vibrant. Due to the wet nature of the medium, you can mix oil pastels on the canvas or on a palette like paints.
Pastel Pencils
A more modern drawing tool, pastel pencils fuse the color effects and texture of pastels with the convenient cleanliness of colored pencils. In these implements, a sheath of wood encases a core of chalk-based pastel. You may sharpen a pastel pencil in a standard handheld pencil sharpener. Pastel pencils are suitable for clean, detailed drawings with a pastel look.
