Wishab sponges receive a great deal of praise for their ability to cleanly and conveniently remove surface soil from walls, ceilings, pictures, frescoes, mural paintings, wallpaper, paper, textiles, books, coats of paint, and more. Sponges absorb dirt and then crumble as you work to avoid damaging the surface being treated. After rubbing an area, simply vacuum or sweep away the residue. Made of vulcanized latex formed onto a stiff blue nylon backing, they have a neutral pH and are available in three degrees of firmness. The soft sponge is designed for sensitive surfaces, the hard sponge for less sensitive surfaces, and the extra-hard sponge is designed for non-sensitive surfaces, such as stone. Surfaces must be completely dry prior to use. Test gently in an inconspicuous are to be sure the surface does not stain or chalk. Akapad (Wishab) materials have been safely used for more than twenty years and support for them is growing steadily. Each sponge is approximately 3-1/2 x 2-1/2 x 1-3/4 in.