Hi....If you add liquid detergent to your black tempera paint, if will help
with the adhesion of paint to wax crayon. This way you won't have to make
the paint extra thick to cover and it will prevent cracking/chipping.
I like to do one particular mid. school project with scratch art like this
and we make the tempera (black) watery over the diff. colored areas so it's
more of a gray tone of black. This way, when they scratch, they can see the
area they are working on and can keep the same pattern within the
one-colored area and then change the pattern for another colored area.
(This might be as clear as mud to some of you...hope not.) Toodles...
Bunki Kramer - Los Cerros Middle School
968 Blemer Rd., Danville, California 94526