Removing Crayon Marks on a Blackboard
Rough sponges can also damage the finish. Make a simple paste with baking soda and water. It should have the consistency of icing. Apply it to a soft clean rag, and gently rub away the crayon marks. Wipe away the baking soda with a clean rag and clear water.
It is not necessary to apply a lot of pressure while cleaning with a Mr. Clean Magic Eraser or a similar sponge of a different brand. It will work like magic, and lots of elbow grease is not required to remove tough stains.