Evaluation of Accelerated Ageing Tests for Metallic and Non-Metallic Graffiti Paints Applied to Stone

Abstract

Abstract:Graffiti are increasingly observed on urban and peri-urban buildings and their removal requires a huge financial outlay by local governments and agencies. Graffiti are not usually removed immediately, but rather over the passage of time, viz. months or even years. In this study, which forms part of a wider research project on graffiti removal, different methods (gravimetric analysis, examination of digital images, colour and infrared measurements) were used to evaluate the performance of accelerated ageing tests (involving exposure to humidity, freeze-thawing cycles and NaCl and Na 2 SO 4 salts) for graffiti painted on stone. Silver (metallic) and black (non-metallic) graffiti spray paints were applied to two types of igneous rock (granite and rhyolitic ignimbrite) and one sedimentary rock (fossiliferous limestone, i.e., biocalcarenite). The metallic and non-metallic graffiti spray paints acted differently on the stone surfaces, both chemically and physically. Older graffiti were found to be more vulnerable to weathering agents. The ageing test with NaCl and particularly Na 2 SO 4 , both applied to granite, proved the most severe on the paints, yielding more detrimental and faster artificial ageing of the type of material under study.

A Study on the Suitability of Mechanical Soft-Abrasive Blasting Methods to Extract Graffiti Paints on Ornamental Stones

“…The identification of blue graffiti paint remains was performed through the detection of low contrast C-rich deposits with Ti, Si, and Al (Figure 4a), and silver graffiti was identified through high contrast particles of Al embedded in C-deposits ( Figure 4b). This composition was already identified in previous works [20,31,32]. Under SEM and with stereomicroscopy observations, a higher amount of graffiti remains were found on surfaces cleaned with DIB, mainly in the case of blue graffiti (Figure 4-granite and Figure 5-limestone).…”

Accelerated Ageing Procedures to Assess the Stability of an Unconventional Acrylic-Wax Polymeric Emulsion for Contemporary Art

“…The measuring head (3 mm diameter) was placed, with the aid of a positioning mask, on the same area of glass slide film samples before and after the accelerated ageing. In the field of Heritage Science, generally, ΔE values higher than 5 are not acceptable since the total colour variation is clearly detectable [ 34 , 35 , 36 ].…”

Biocleaning to Remove Graffiti: A Real Possibility? Advances towards a Complete Protocol of Action

“…Specimens of granite and concrete (4 × 4 × 1.5 cm 3 ) with bush hammered finish were coated with layers of each selected colour of graffiti spray paint following the method described by Sanmartín and Cappitelli [2] (Figure 3). Once painted and dried, the specimens were sterilized following the protocol described by Sanmartín et al [10].…”

“…Colour measurements were made with a portable chroma meter (CR-300, Konica Minolta, C Minolta, Osaka, Japan) with a 8 mm-diameter viewing area in the measuring head. Previously described methods, from which we know the minimum number of measurements required, were used for the powered graffiti [24] and the painted stone specimens [2]. The measuring conditions were as follows: (1) Diffuse illumination geometry with the specular component included in 0 • (d/0 • ) relative to normal, (2) illuminant D65, and (3) observer 2 • .…”

“…Many affected sites are considered deteriorated and thus lose some of their economic value. In the preservation of public spaces and historic buildings, graffiti removal (i.e., removal of aerosol spray paint, the most commonly used staining agent) requires a huge financial outlay by local governments and agencies; e.g., in 2008, the cost of removing graffiti from buildings in the city of Santiago de Compostela (Spain) amounted to more than €150,000 [2].…”