Removing Graffiti from Historic Masonry (Part C)
Testing
Before selecting a removal method, all cleaning materials and techniquesfor removing graffiti from a historic masonry building should be testedon mock-ups or areas of the resource that are not highly visible, but whichare representative of typical conditions. Visual observation should besupplemented by the use of a magnifying glass, and spot tests should becarried out with various solvents to help identify the specific graffitimedium, which will aid in its removal. More complex testing using laboratoryequipment and more scientific analytical processes may sometimes be necessaryin complex situations. Sample areas that represent the desired degree of"cleanliness" should be approved in writing by client, architect,conservator or other appropriate authority. The materials and all the otherdata necessary to reproduce the desired cleaning results should be meticulouslyrecorded and the accepted sample area preserved for reference until theend of the job. The existence of a "clean" sample for comparisonand a signed agreement can avoid unpleasant surprises, misunderstandings,and perhaps legal actions.
When a type of graffiti appears for the first time that was executedwith a material not immediately recognizable and for which no countermeasureshave been developed, tests may need to be carried out by an architecturalconservator to identify the material and to determine effective removaltreatments. Agencies with large inventories of graffiti-prone buildingsand structures should watch for graffiti made with new materials and experimentwith different cleaning methods in order to be prepared when it appears.Such early action can save large sums of money in the long term. (See "Developmentof a Treatment Plan.")
