Clean Galena was developed for the cleaning of culturally important buildings with natural stone facades. It can be used to remove the dust and dirt that builds up over the years, as well as other impurities, from mineral surfaces such as limestone. This single-component product is based on clay minerals and dries to form an easily removable skin which binds heavy metals, dust and dirt deposits, and gently detaches them from the stone. As well as removing deposits, Clean Galena can also eliminate stains on the surface that are caused by iron or copper compounds. The product is emission-free and no water is used in its application. The cleaning action comes from a range of readily biodegradable complexing agents. Clean Galena prevents the harmful heavy metals present on the facade from being released into the environment. This means that the time-consuming step of covering up the surfaces can be completely dispensed with.