Some will not appreciate his use of devices which he justifies with camera obscura
and devices of old masters....however, check out his "Studio Tips"
then go down to "Erasing with wall putty" and click on links there.
He has a really neat idea of using wall putty to erase and use as
subtractive/negative space drawing. The wall putty acts as a graphite magnet
picking up graphite without ANY damage to the paper's surface, and offers much
control over effects. Better than gum erasers or kneaded. The putty can be
shaped to be a quite enabling tool. I'm definitely going to try it....and then
introduce my students to it. -Larry