Table 1.
List of tests and slab sizes.
Fig 1.
Climatic conditions for the outdoor exposure trial.
Light grey bars represent the time in the field and the dark grey ones the time in the lab.
Table 2.
Physical properties of the stones before and after being coated with the permanent (AG1) and sacrificial (AG2) anti-graffiti coating.
Fig 2.
Stereographic microscopy images of the surface of limestone.
Untreated (a) and coated with AG1 (b) and AG2 (c): unweathered (0), after 12 months of outdoor exposure (1) and after1500 hours (2) in a QUV chamber.
Fig 3.
Stereographic microscopy images of the surface of sandstone.
Untreated (a) and coated with AG1(b) and AG2(c): unweathered (0), after 12 months of outdoor exposure (1) and after 1500 (2) and 2000 hours (3) in a QUV chamber * Just the right half of the sample has been exposed to UVB radiation.
Fig 4.
Micro-Raman spectra of the coated surfaces of limestone (a) and sandstone (b) AG1 (1) and AG2 (2) before (0) and after being weathered for 500, 1000, 1500 and 2000 h in a QUV chamber. Spectra of the uncoated surfaces (UT) and of the treatments (AG1 and AG2) are also shown as references.
Fig 5.
From top to bottom; Changes in colour coordinates, L* and b*, total colour variation (ΔE*) and gloss of limestone and sandstone.
Untreated (UT) and anti-graffiti treated surfaces (AG1 and AG2), artificial (QUV) and natural weathering (Wytham) at different months of outdoor exposure or hours in the chamber.
Fig 6.
Contact angle of the anti-graffiti coated surfaces of limestone and sandstone after natural and artificial weathering.
Fig 7.
Pictures of graffiti removal on limestone slabs (150x75x10 mm).
Untreated (UT) and protected with AG1 and AG2 anti-graffiti coatings, unweathered (UW) and natural (W) (3,6 and 12 months) and artificial weathered (W) (500, 1000 and 2000 h). Unweathered and natural weathered samples show two different cleaning procedures: top bottom (a), detergent and brush and half bottom (b), detergent and high pressurized water spray. The former is used on the marked (irradiated) area of the artificially weathered samples. Close-up images taken with a stereoscopy microscope.
Fig 8.
Pictures of graffiti removal on sandstone slabs (150x75x10 mm).
Untreated (UT) and protected with AG1 and AG2 anti-graffiti coatings, unweathered (UW) and natural (W) (3,6 and 12 months) and artificial weathered (W) (500, 1000 and 2000 h). Unweathered and natural weathered samples show two different cleaning procedures: top bottom (a), detergent and brush and half bottom (b), detergent and high pressurized water spray. The former is used on the marked (irradiated) area of the artificially weathered samples Close-up images taken with a stereoscopy microscope.
Fig 9.
Overall colour changes on the surface of limestone and sandstone after graffiti removal.
Untreated samples (UT), treated with AG1 and AG2 anti-graffiti coatings unweathered (UW) and artificially (500, 1000 and 200 h in a QUV chamber) and natural (3, 6 and 12 months of outdoor exposure) aged
Fig 10.
Roughness (Rz, μm) of the unweathered and weathered anti-graffiti coated surfaces after all episodes of graffiti removal.
Reference values of the roughness of the samples without anti-graffiti coatings and with AG1 are displayed (not the ones for AG2 coated samples since this treatment does not modify the roughness of the stones).