Evaluation of a protective acrylic finish applied to surfaces painted with acrylic paints for outdoor or indoor uses

Protection of contemporary murals to reduce paint fading caused by exposure to sunlight is currently under study due to a general demand. In this study we evaluated the effectiveness of a commercial protective acrylic finish applied to concrete and brick mock-ups previously painted with different coloured (red and yellow) paints for outdoor and indoor uses. The mock-ups were exposed to an accelerated aging test, with artificial UV irradiation for 3630 h. UV radiation is the most threatening sunlight portion to the paints used in these artworks, inducing mainly fading. Colorimetric measurements were made on the surfaces every 15 days. At the end, aged samples and the respective controls (not subjected to the aging test) were evaluated by stereomicroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Application of the protective finish modified the surface of the paintwork, but generally reduced the rate at which the colour changed. In the mock-ups painted with paint for indoor use without the protective finish, the paintwork degraded faster on brick than on concrete. The findings highlight the need for appropriate selection of paints depending on where they will be applied and the suitability of using a protective finish depending on the composition of each paint.