When I use those things on drywall, it produces "sawdust", for lack of a better term. Or, just like a regular eraser for pencil, you get the eraser rubbing off and the graphite mixed in with it, producing that dark gray residue that you whisk of blow off the paper. Similarly, the Mr. Clean Magic Eraser is consumed when you use it. Won't that stuff end up below the keys and muck things up? Or, can you just blow it out with compressed air?