Pastels are colored pigment in the form of a stick (or encased in a pencil) consisting of the pure powdered pigment and a binder. The pigments are the same as used in other art mediums such as oil paint, where the pigment is in an oil based suspension. The binder used for pastels is of a neutral hue and low saturation, making the color closer to the natural dry pigments than those of any other process.
Pastels have been used by artists since the Renaissance, however the technique of applying pure dry pigment to a surface is one of the oldest art forms known. The cave paintings found in Pettakere cave in Sulawesi are dated at about 35,000 years old.
Care & Handling
Unless you plan to seal your pastel paintings in a cave, they should be handled with care and kept protected. Framing under glass is the best way to display and protect them. Do not use acrylic or materials like Plexiglas as they have the ability to build up a static charge and lift fine pastel dust particles off of the paper and onto the acrylic. Also avoid keeping pastel paintings in excessively humid rooms.
When framing use a float mat. That is a mat that is between the original and any visible mat(s). The float mat will have a larger opening than the visible mats and will be unseen. This allows any pastel dust (not that much would) to fall into the gap and not onto the bevel of the visible mat(s).
If you need to store a pastel painting unframed or without glass, cover the work with glassine.