The Building Conservation Directory 2022

PROTECT ION & REMEDIAL TREATMENT 4.1 131 C AT H E D R A L C O MM U N I C AT I O N S 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 2 2 RESPONDING TO A GRAFFITI INCIDENT AND THE RISKS OF HASTY CLEANING ATTEMPTS Due to the tendency for graffiti to proliferate, there is often a push to remove freshly applied graffiti as rapidly as possible, to discourage further incidents and demonstrate that repeated attacks will not be tolerated. This is understandable but a balance needs to be struck between rapid removal and taking the time to procure effective cleaning services from an informed and suitably skilled contractor. Unfortunately, hasty removal attempts carried out without assessment and understanding of the graffiti type (medium), the surface (substrate) type and condition often result in further surface disfiguration. Readily available cleaning methods, such as mechanical cleaning (using pressurised water or abrasive) and scrubbing with metal bristle brushes, are designed for robust modern materials such as concrete, and are too aggressive for historic building surfaces. The damage caused by routine removal of graffiti using such methods is readily visible in places where repeated removal has been carried out on historic facades. The scratches, scouring and other marks left by such removal attempts are permanent. Incomplete removal often mobilises coloured components of the graffiti medium, fine pigment and other particles, causing these to ‘bleed’ and spread, penetrating into small surface pores and often becoming more difficult or impossible to remove completely. Soft, porous, and open textured surfaces/ materials, for example Bath stone and hand- made bricks are particularly vulnerable to damage. Assessment and understanding of the surface type and condition is essential to prevent unnecessary damage and ensure effective graffiti removal. In some cases, it may be advisable to conceal graffiti with temporary barriers or covers, rather than attempt removal without the necessary resources and skills in place. This may be the preferred solution for graffiti that features offensive text or symbols, or that constitutes a hate crime, motivated by hostility or prejudice based on race, religion, sexual orientation, or disability. Offensive graffiti may be covered in several ways, subject to site and logistical constraints. Free standing monuments can be concealed using wraps (opaque sheeting) secured in place with adjustable ties or straps. Opaque sheeting may be draped over vertical surfaces and secured with timber battens, provided fixings for these are sensitively located, typically in mortar joints to minimise the impact on historic fabric. On free standing walls it may be possible to drape protective sheeting over the face, with weights integrated, as in the hem of a curtain, to secure the cover in position. In exceptional cases, the option of applying a temporary coating over graffiti, using a material such as limewash or sheltercoat, may be appropriate, subject to consideration of the need to subsequently remove this coating as well as the underlying graffiti. An important first step in response to any graffiti incident is to obtain photographs that capture the graffiti both in the site context and in detail. The photographic record should include general views, to illustrate the scale of the graffiti and details of the graffiti medium (or media if more than one type of material has been applied). A photographic record is essential for every subsequent step – procuring cleaning advice and removal services, making an insurance claim for the damage, and taking legal action. It is important to check the legal status of the building and confirm the need for consent prior to carrying out any cleaning or other remedial work. Again, photographs are helpful in this context, to illustrate proposals for cleaning and any other work, for submission to statutory authorities. GRAFFITI MEDIA AND VULNERABLE HISTORIC SURFACES Safe and effective removal starts with an understanding of the building surface (substrate) and the medium used for the graffiti. Spray paint is by far the most common medium, but marker pens and ink pens are also used, as well as other portable materials such as nail varnish and lipstick. The binders, solvents, dyes, pigments commonly employed in these and other media vary significantly, and a cleaning method suitable for one medium may be unsuitable for another. Understanding the composition of the graffiti medium is key to assessing how the graffiti marks respond to proposed cleaning methods. Graffiti inscribed or scratched into a surface cannot be removed without further damaging the surface. However, depending on the surface material, it may be possible (if a suitably skilled contractor is engaged) to fill the incisions or scratches, to make the graffiti illegible or at least reduce its legibility. The surface type and its physical characteristics determine how it will respond to cleaning (graffiti removal). Soft, porous limestones, hand-made bricks, and lime-based plasters and coatings can all be classed as vulnerable to damage using aggressive cleaning methods. In general, it is not possible to remove graffiti effectively from such surfaces using non- specialist (generic) cleaning methods, Graffiti inscribed on the jamb of a medieval arch in a tunnel at Dover Castle, including the double V (Marian mark) thought to invoke the protection of the Virgin Mary. Such marks are easily overlooked, especially in underground locations, in tunnels, caves, and mines, where lighting and visibility is poor. Use of raking light (as in these images) can significantly improve legibility. 3D scanning can also be helpful in recording, deciphering and interpreting such marks. Theeffectsofrepeatedattemptsatgraffitiremoval fromBathstoneinclude ‘ghosting’, thefaintgraffitioutlineremainingvisibleduetofineparticlesofmediumpenetrating into the surface, and a jarring contrast between the bleached appearance of some cleaned areas in comparison to the darker, soiled areas. This contrast could have been reduced by extending the cleaning to the architectural lines (the vertical and horizontal projections). Scratching and other marks left by an attempt to remove graffiti from Bath stone, a relatively soft and porous material