Protection of contemporary mural artwork: Evaluation of a fixing primer and colour protectors

Application of a fixing layer prior to the paint or/and posterior application of a colour protector are conservation strategies used in contemporary murals to reduce the deterioration of the artwork when exposed outdoors agents, mainly solar radiation and humidity. In this study, the physical, chemical and mineralogical changes in 4 alkyd (yellow, pink, orange and green) and 2 acrylic (fluorescent orange and fluorescent green) paints applied to concrete mock-ups were evaluated under different conditions. Concrete test slabs were coated with a fixing layer prior to application of the paint and/or posterior application of a protector (2 different acrylic colour protectors). Samples were exposed to the QUV accelerated weathering test for 1512 h. Colour monitoring was carried out during the test. A multi-analytical evaluation protocol based on stereomicroscopy, contact angle measurement, peeling test, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy was used to assess the physical, chemical and mineralogical changes in the samples after the exposure period. The findings revealed that the green alkyd paint was most resistant to colour changes, while the orange alkyd and the fluorescent acrylic paints (orange and green) underwent the most noteworthy colorimetric changes. Unexpectedly, the fixing layer did not slow down the colorimetric changes in the paints. Although there were some differences in the performance of the products evaluated, applying a colour protector can help to conserve murals but can also affect the original colour of the paint. • Acrylic and alkyd paints with/without protectors exposed to accelerated ageing test • Fixing primer does not slow down colorimetric variations. • Coating failures are influenced by the paint and protector composition. • Acrylic-based paints undergo the most noticeable colour difference. • Colour change could be related to organic phase loss.