BCD 2019

130 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 9 C AT H E D R A L C O MM U N I C AT I O N S CAN MASONRY CLEANING EVER BE CONSIDERED TRULY SAFE? JAMIE FAIRCHILD W HEN CONSIDERING the safety of road travel, the risks involved might appear straightforward to quantify; we could examine the statistics for serious injuries sustained per kilometre of a particular road and compare this with other routes. However, perhaps we should include minor injuries in our calculations or compare the risk of travelling our chosen route with that of staying at home? Likewise, where the safety of masonry cleaning is concerned, will cleaning inflict more damage than leaving the soiling or coating in situ and how do we define successful cleaning? The reality is that the outcome is difficult to quantify and safety is most often relative rather than absolute. Instead we concentrate on minimising risk, managing expectations and paying close attention to the factors within our control – the cleaning equivalent of passing a driving test, maintaining a safe vehicle, adopting a recommended route and keeping within the speed limit. Firstly however, is the journey, the process of cleaning, actually necessary? REASONS FOR CLEANING In general, the primary motives for cleaning are aesthetic and hygienic. For buildings, particularly historic structures, we might have additional or alternative objectives. The following are the principal technical reasons for cleaning: • remove soiling or coatings harmful to the masonry • reveal defects and facilitate a condition survey • enable repair, repointing or redecoration • preparation for additional treatments • remove toxic residue or coatings • improve legibility and facilitate recording • enhance the historical significance • increase light reflection for visibility and safety. The following are broadly aesthetic or commercial aims: • harmonise existing and repaired masonry • engender social wellbeing, pride or respect • remove disfigurements caused by a traumatic event • fulfil the requirements of a lease • demonstrate project expenditure • increase commercial value. The presence of significant dirt is normally regarded as a sign of neglect. Even so, the cleaning of a listed building for aesthetic appearance is generally given a low priority by those providing consent. Quite rightly we will be asked to justify the need, the method used and the degree of cleaning. The reasons for this include the perceived risk of physical damage and potential loss of historical patina. It is likely that any cleaning, however gentle, will result in some surface loss even if not readily visible to the eye. Nonetheless, thoughtful A cleaned limestone capital demonstrates an agreed cleaning method (wet air abrasive) method and level of clean. (Photo: Restorative Techniques Ltd)