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.
Types of dry pastel:
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 colours. 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; hairspray also works, although caution should be taken, as fixatives may affect the colour or texture of the drawing. White chalk may be used as a filler in producing pale and bright hues with greater luminosity.
Pan pastels: These are formulated with a minimum of binder in flat compacts and applied with special Soft micropore sponge tools. No liquid is involved. A 21st-century invention, pan pastels can be used for the entire painting or in combination with soft and hard sticks.
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. Hard pastels are traditionally used to create the preliminary sketching out of a composition. However, the colours are less brilliant and are available in a restricted range in contrast to soft pastels.
In addition to dry pastels, others are manufactured in a different way:
Oil pastels: These have a soft, buttery consistency and intense colours. They are dense and fill the grain of paper and are slightly more difficult to blend than soft pastels, but do not require a fixative. They may be spread across the work surface by thinning with turpentine.
Water-soluble pastels: These are similar to soft pastels, but contain a water-soluble component, such as Polyethylene glycol. This allows the colours to be thinned out to an even, semi-transparent consistency using a water wash. Water-soluble pastels are made in a restricted range of hues in strong colours. They have the advantages of enabling easy blending and mixing of the hues, given their fluidity, as well as allowing a range of colour tint effects depending upon the amount of water applied with a brush to the working surface.
There has been some debate within art societies as to what exactly counts as a pastel. The Pastel Society within the UK (the oldest pastel society) states the following are acceptable media for its exhibitions: “Pastels, including Oil pastel, Charcoal, Pencil, Conté, Sanguine, or any dry media”. The emphasis appears to be on “dry media” but the debate continues.
Sidewalk chalk is typically large, coloured (and sometimes white or cream) sticks of chalk (calcium sulphate rather than rock chalk, calcium carbonate) mostly used for drawing on pavement or concrete sidewalks. It is sometimes used by children to draw a four square court or a hopscotch board. Blackboard chalk is typically shorter.
Sidewalk chalk is used at some universities to advertise for events, especially where there is much concrete. Prohibitions are set for where students can chalk, usually limiting it to areas that will be washed away with rain, or areas which are set to be cleaned of chalk markings.
Some teachers promote use of sidewalk chalk on a carpet as an interactive teaching tool. Although sidewalk chalk is created to allow people to draw on sidewalks or pavement, some law enforcement agencies may prohibit sidewalk drawing in certain areas without first being requested for authorization.
Artists such as Kurt Wenner, Ellis Gallagher and Julian Beever have created intricate and realistic street paintings using the chalk and pastels. It is typical for sidewalk chalk artists to use anamorphic drawing when drawing with sidewalk chalk. Non-anamorphic drawing are drawings that are drawn to be observed face-on, whereas anamorphic drawings are drawn to be observed from a different viewpoint.
There are several different types of sidewalk chalk, typically coming in solid-coloured sticks. 3-D sidewalk chalk sets, in which each stick of chalk is created with two particular colours that appear 3-dimensional when viewed through the 3-D glasses that come with the chalk, also exist.