Influence of material optical characteristics on vision and fruition of Cultural Heritage

For Cultural Heritage materials is important to guarantee a correct conservation and vision of the artefacts, enhancing the observer experience assuring the best visual and conceptual appearance of artefacts. Several factors affect the visual appearance of artistic materials. However, available measurement methodologies for the material characterisation are not able to accurately predict the visual appearance of materials usually used in cultural heritage. Goals of the thesis research was to identify the visual attributes that mainly affect the appearance of artworks, investigate the correlation between measured data and visual human response and individuate if there are measured conditions that allow a better correlation. Finally, provide useful suggestion to aid in planning and selecting adequate conservative intervention, such as restoration work. In order to reach these purposes, different samples representative of materials used in artistic artefacts were selected and realised and two different visual testes were set up and carried out investigating the influence of lighting and viewing conditions on the human visual response of selected visual attributes: glossiness, colour (saturation), brightness and sparkling. The first visual test takes into account how the human visual responses on glossiness and saturation are affected by the lighting and viewing conditions using coloured samples with different levels of gloss obtained brushed on them different mixture of natural varnishes. While, in the second visual test were identified the elements that mainly affect the human perception of sparkling and brightness in monochromatic samples with mica particles, a mineral easily found in ornamental stones. At the end of each visual test, all responses were statistical analysed and, then, the results were compared with the corresponding objective measured data. In this way, it was possible to define what measurement conditions allow to have a better correlation with the subjective assessment.