Wall tiles with semi-sheen to gloss surfaces can be washed with a soft rag or sponge and mild detergent. A green 3-M scrub pad can be used gently to remove scuffmarks on most glazes. The blue glaze can scratch so test a small area to learn its limits. Tiles with matte and porous surfaces should be treated much as one would treat suede; use a clean, non-lint tool such as a toothbrush or lint free cloth to gently lift the dirt out of the glaze pores. Mild soap and water can be used.