Incompatibility risk assessment procedure for the cleaning of built heritage

A procedure is proposed to assess the compatibility of cleaning actions to be carried out upon built heritage. This procedure was designed as a semi-quantitative (in)compatibility risk assessment, where the vulnerability of the substrate to cleaning, the aggressiveness of the cleaning method and the substrate/method synergies are factors considered to determine the likelihood of damage occurring, whereas the impact on the significance of the object measures the consequences of damage occurring. Rating these factors of likelihood and consequences of damage allows a cleaning risk matrix to be proposed for the evaluation of the risk levels implicated by different cleaning methods. Furthermore, planning components entirely contingent of their specific actors, and therefore inherently difficult to grade, such as operator skills or control adequacy, are included as quality components, which work as multiplying parameters of the overall risk. The procedure was conceived to assist in and frame the planning of built heritage cleaning actions. A Delphi Panel of conservation experts was convened to validate this proposal.