This paper seeks to enquire as to why it should be that, after nearly two centuries of cleaning controversy at major museums, we have reached a point where three different approaches to cleaning are widely employed. The fundamental problem of change in paintings - the long lost relations - forms the starting point of the discussion, with the recognition that old paintings simultaneously incorporate changes that are seen as loss, such as faded pigments, and changes that have come to be culturally valued as signifiers of the passage of time. We cannot return to the original intention and so must construct a new relationship between the artist's original intention, the present work, and the passage of time. But there can be no single - no absolute - solution to such a problem; rather, there are a number of new found relatives. Experience with the practice of cleaning has led to just three cleaning systems - complete, partial, and differential - finding favour. What they share in common, and what gives each a parallel validity, is that they establish a definably coherent relationship to aspects of the artist's intentions and the passage of time. Once cleaning is understood in these terms, it is possible both to accept the validity of all three different approaches, and to identify the critical points within any particular cleaning system at which the coherent relationship mey be jeopardised. From this basis, conservator and curator can share responsibility for what is done during cleaning.