Whenever I draw in it, and fold the previous page over to the back, this is what the back of the page will pick up. Dust, dirt, grime, etc. Not cool.
Behold my solution!
You know how sometimes paper packs or other items come with a piece of cardboard in the back? And you know how some of you like to save these? I raise my hand here as well since I do it too...
I cut the cardboard to size, and used a hole punch to make the spaces for the spiral ring binding. I then cut the space between the punches to the edge of the cardboard a little so they could easily be switched from page to page.
Et, Voila! No more dirty pages. The cardboard piece is now at the back of the book while I draw. Added bonus? I always know exactly which page I am working on. It's like a gigantic tab.