Pastels are made from safe base as are all other fine art paints, including oils and acrylics. The difference is the binder. Pastels use very little binder so it is almost like apply direct pigment to canvas.
Pastels are not chalk. Chalk is made from limestone. Pastels are totally different. Pastels are one of the oldest and most enduring foundations for hand painted portraits.
Pastel paintings do not check, crack, flake or darken because there are no additives, such as oil, to cause them to do so. Therefore it is considered the most permanent of all media.
It is important to have pastel portrait paintings framed under glass. Matting board should be used so that the painting does not rest against the glass. And like all fine art, keep it out of direct sunlight.
A canvas that is entirely covered is called a pastel painting, a canvas that is only partially covered is called a pastel sketch.
Pastel paintings hold their value. Some by Degas from the 19th Century sold for $3,000,000 each.
Pastel is a French word meaning pure, powdered pigment ground into a paste, with a tiny amount of binder. There is an infinite variety of colors ranging from subtle to bold and brilliant. Pastels are not synonymous with “pale”; rather, pastels create vibrant, luminous dark and light hues. They create depth and add magnificent reflective qualities to the painting.
Soft pastels have high pigment which yield brilliant color to a painting. Hard pastels are used for detail work and quick sketching. The artist may use pastel pencils as well for fine detail