Pastels last a very long time, they never turn yellow or fade, they are pure pigment with a TRAGACANTH binder. The binder comes from the astragalus scrub in Asia-Minor.
To protect the pastel painting lightly spray it, today there are good acrylic fixatives. After the fixative dries the colors will be slightly muted. The last step is to brighten the highlights with more pastel. Be sure the glass covering the picture is at least 1/8 inch away from the picture.
