Kneaded Rubber—Kneaded rubber erasers absorb graphite, charcoal, carbon, and pastels to lift or blend colors and add highlights. Also known as gummy erasers and putty rubber, they are often used for architectural or engineering drawings. Mold them into any shape for use on large areas or for detail work. Unlike other erasers, these won’t leave residue behind or wear down, so they last longer. To clean them, knead until the pigment is absorbed into the rubber. Discard them when the eraser becomes hard.