Erasers work in relatively the same way that soap does. Let’s look at the tree elements; the paper, the graphite, and the eraser. The molecules that comprise the paper have lots of ridges and bumps, microscopically. When you write graphite is worn off the pencil tip, the graphite molecules interlock with the paper molecules. Then comes the eraser. The eraser’s molecular surface is something that the graphite likes to stick to more than paper. As the eraser is rubbed and worn on the page, most every graphite molecule it touches has a better bond with it than the paper. The eraser “dust” that is left over is worn off eraser with graphite stuck to it. If an eraser is wet, the water molecules are locking into the eraser molecules, preventing the graphite from bonding as it would otherwise, and smears your text around.