We decided to put the sponge to work on a wall in the station — one we knew would be knocked out for renovations. Then we brought in some kids and asked them to draw and color all over the wall. Needing no encouragement, the kids quickly went to work.
For the cleanup, we added water to the sponge as directed and wiped the walls down.
The result? At first, the eraser smeared the the crayon all over the wall, but in the end — and with a lot of scrubbing, the eraser took all the crayon off the wall and with it some paint. The eraser left the pencil on the wall.