This paper discusses the aesthetical aspects of ageing and focusses on the use of the terms ‘patina’ and ‘damage’ to decide on the cleaning of historical facades and the application of artificial ageing. Conservation campaigns can be characterized by the wish to preserve an object, building or building complex as a coherent piece of Cultural Heritage. This paper discusses the professional debate on balancing between preserving values, i.e. represented by patina and the need to intervene from a technical point of view. Cases on cleaning of limestone and sandstone together with replacement of natural stone and the application of artificial ageing are used to illustrate the debate. The perception of professionals is compared with the perception of laymen.