Experts both in Hungary and abroad often have different - even opposing - views on how to clean and conserve the crumbled and contaminated surfaces of limestone or marble. In order to apply the appropriate stone-cleaning methods, one has to be aware not only of the physical and chemical properties of the crumbled stone surface but also of the stone cleaning and conserving agents and how they affect the stone. Without this information, both the cleaning and the subsequent conservation treatment might have a damaging effect on the stone objects in museums and monuments. See also AATA 21-490.