Dry-cleaning sponges are made of vulcanized rubber. A miniscule percentage (less than 30 grams per 500 kilograms of sponges) of mild soap is impregnated during the manufacture of the sponges. Their unique pore size effectively removes dirt, soot, and smoke residue from a variety of substrates including walls, books, wood, paper (including wallpaper), textiles, and metal. Ideally use the sponge by applying a light even sweeping motion in one direction over the surface to be cleaned, taking extra care not to use a scrubbing motion, and always use completely dryEach sponge measures 152 x 76 x 19mm.