I have been expirimenting with this technique that illustrator Barron Storrey told me about. It is a mixed medium technique that involves acrylic painting, sealing the painting with matte medium, working with colored pencil on top, sealing again with matte medium, working with paint/pencil, and sealing, etc. Now when I try to work on top of matte medium with colored pencil, it has a tendency to chip the surface all the way to the white of the board. I recently did a oil painting on gesso board (with liquin to make the paint dry overnight) then I applied matte medium and tried to work on top with colored pencils and the same chipping occurs. I tried sealing the painting with both Krylon Crystal Clear and Workable fixative and the surface still sucks. Dont know why they call it workable fixative when you really cant work on it since it gives you a crappy pencil stroke. Any idea on whats going on with this matte medium? Am I using it improperly?