Influence of the Distribution of a Spray Paint on the Efficacy of Anti-Graffiti Coatings on a Highly Porous Natural Stone Material

Abstract

Graffiti on facades often has a heavy impact in social and economic terms, particularly when historical and artistic artefacts are affected. To limit the damages to the surfaces, preventive plans are implemented and anti-graffiti coatings are used as a protective measure. In this study, the distribution of a spray paint inside a highly porous stone, with and without anti-graffiti protection, was investigated. Two commercial sacrificial anti-graffiti systems were used and an acrylic-based paint was applied as staining agent. Environmental scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) microanalysis were performed to characterise, from the morphological and chemical point of view, the anti-graffiti coatings and the paint. Maps of the main elements were acquired to locate the different products inside the stone. Chemical removers were used to clean the stained surfaces, then the effectiveness of the cleaning was assessed by visual observations and colour measurements, as well as on the basis of percentage of residual stain. The obtained results highlighted that the anti-graffiti efficacy strongly depended on the characteristics of the applied coating. This latter usually acted as a barrier, but good results were obtained only where the stain did not remain as a separate layer, but penetrated the protective coating. Microcracks in the anti-graffiti coating were able to nullify the protective action.

Novel Nano-Filled Coatings for the Protection of Built Heritage Stone Surfaces

“…In the literature, several methods are reported to quantify the efficacy of stain removal based on the residual stain [ 32 ] or examining the ΔE* ab after the cleaning [ 44 ]. Similarly, cleaning efficacy (CE) above 90% means effective stain removal while CE below 80% cannot be accepted; CE between 90% and 80% are tolerable values, although not optimal.…”

“…Where the protective coatings were applied, the cleaning with acetone allowed removing the paint to a certain extent but this procedure did not give acceptable results. The cleaning was more effective in the compact stone; on the other hand, the paint on a highly porous stone can be barely removed because it easily penetrates beneath the surface and is retained into the pores [ 32 ]. In addition, the results confirmed the stronger action of the felt-tip marker in comparison to other staining agents.…”

“…The cleaning efficacy (CE), referred to the removal of spray paint or marker, was evaluated as a percentage by Equation (5): CE = {1 − [(ΔE* ab ) cleaned /(ΔE* ab ) stained ]} × 100, where: (ΔE* ab ) cleaned is the color variation of the cleaned surfaces; (ΔE* ab ) stained is the color variation of the stained surfaces and the ratio (ΔE* ab ) cleaned /(ΔE* ab ) stained is the residual stain [ 32 ].…”

Characterization of spray paints used in street art graffiti by a non‐destructive multi‐analytical approach

“…4,8,9 On the other hand, when graffiti spray paints are associated with acts of vandalism, knowledge of their chemical composition is also essential in deciding for the appropriate and most effective cleaning method. [10][11][12] Similar to modern paint materials, graffiti spray paint formulations are complex mixtures of various major and minor components: pigments/dyes, used to provide color; solvents, allowing the mixture to flow; additives, such as emulsifiers, light stabilizers, antioxidants, plasticizers, etc., used to improve specific properties; and binders, used for holding the mixture together and creating adherence to the surface. 4,13 Such complex mixtures are difficult to characterize due to the high heterogeneity of the system.…”

“…Characterization of spray paints and understanding of their chemical composition is essential in providing key information for the documentation and long‐term conservation strategies of both street art graffiti and mixed‐media murals 4,8,9 . On the other hand, when graffiti spray paints are associated with acts of vandalism, knowledge of their chemical composition is also essential in deciding for the appropriate and most effective cleaning method 10‐12 . Similar to modern paint materials, graffiti spray paint formulations are complex mixtures of various major and minor components: pigments/dyes, used to provide color; solvents, allowing the mixture to flow; additives, such as emulsifiers, light stabilizers, antioxidants, plasticizers, etc., used to improve specific properties; and binders, used for holding the mixture together and creating adherence to the surface 4,13 .…”