Abstract
The application of anti-graffiti products to stones belonging to architectural heritage is a common procedure that is currently complementary to traditional graffiti removal treatments, such as chemical and mechanical cleaning. In this study, two anti-graffiti coatings (a sacrificial product and a permanent one) were tested on four stones (with a different texture, mineralogy, and surface finish) commonly found in the historical city center of Turin (Italy). In order to evaluate the effectiveness of the anti-graffiti products, the removal of two graffiti paints with different compositions was tested. The results of the cleaning procedures performed on the surfaces coated with anti-graffiti products were evaluated, considering both the graffiti remains and the alterations induced on the surface. Chemical cleaning based on the use of a low-toxic ternary solvent mixture was applied on the unprotected stones for a comparison with the results obtained on the surfaces coated with anti-graffiti products. The samples were observed under stereomicroscopy and ultraviolet fluorescence photography and all of the treated surfaces were evaluated by roughness measurements, the contact sponge method, static contact angle measurements, and scanning electron microscopy. The composition of the anti-graffiti product, the graffiti paint to be cleaned, and the remover recommended by the manufacturer proved to be key factors for the cleaning effectiveness achieved on coated surfaces. Moreover, to a lesser extent, the mineralogy, texture, and surface finish of the stone also influenced the results of the cleaning procedures. The sacrificial anti-graffiti product enhanced the cleaning effectiveness on all stones if compared to uncoated surfaces; however, the permanence of coating remains on the surface after cleaning proved to be critical. Regarding the use of the permanent anti-graffiti products, intense disparate results were achieved, depending on the graffiti paint composition.
Highlights
As Cultural Heritage is considered a driver and enabler of sustainability for the future by UNESCO [1], ICOMOS promotes scientific studies to enhance the conservation of tangible cultural heritage in the framework of sustainable cities and tourism [2].In the last few years, scientific research on the cleaning of different types of deposits, patinas, and crusts from stones belonging to cultural heritage has been quite rich [1,2,3,4,5]
In the case of travertine, as for the sacrificial product, the accumulation of permanent anti-graffiti product was detected in the voids
Regarding the surfaces coated with the permanent anti-graffiti product, the cleaning treatment texture, mineralogy, and surface finish: polished Baveno granite and Vico diorite, an orthogneiss did not allow the removal of the violet graffiti paint from any of the lithotypes, as already reported (Luserna Stone) with a flamed surface, and a travertine with a disc-cutting smooth surface
Summary
As Cultural Heritage is considered a driver and enabler of sustainability for the future by UNESCO [1], ICOMOS promotes scientific studies to enhance the conservation of tangible cultural heritage in the framework of sustainable cities and tourism [2].In the last few years, scientific research on the cleaning of different types of deposits, patinas, and crusts from stones belonging to cultural heritage has been quite rich [1,2,3,4,5]. Chemical cleaning products are among the cheapest solutions, they may penetrate the substrate and cause irreversible damage, such as chemical contamination, as well as ghosting, due to paint dissolution and its subsequent penetration into the substrate [4,12,13]. They represent a risk for the environment and the conservator-restorer’s health. Considering the cited drawbacks of other cleaning methods, the development of anti-graffiti coatings to protect stone surfaces and facilitate the removal of graffiti paints is justified. There about 21 scientific papers on this topic, mainly focused on carbonate stones [5,11,23], while silicate stones have been less frequently studied
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