The answer came via a Stone business Owner,retired. If you have a smooth surface on Gravestone,clean it with a brush and soap,evtl. SEPIA -Schale (Tintenfisch-Schuppe) (cattle-fish =sepia,Schale means dish) If the surface is rough,then buy a acid free Cleaner for it. Tintenfish -cattle-fish Schuppe -means scale,sqama,dandruff.. Good Luck,Doris with the help of others.