Image-based goniometric appearance characterisation of bronze patinas

Patinas are a form of metal polychromy used to decorate metallic artworks. Due the nature surface, their colour and gloss is perceived differently when illumination viewing directions vary. Sparkle effect on surfaces physical phenomenom caused by micro-facets surface coating which also with changing geometry. In this paper, method designed for measurement sparkle applied goniometric characterisation bronze patinas. Using set six different patinas, in three colours two finishes, it found that these exhibit appearance illuminated viewed at angles. Moreover, roughness patinas measured as expected, increases specular reflection peak decreases. The experiment repeated institutions sets equipment test its repeatability robustness. presented function angle tilting, characterised maximum value full-width halfmaximum. It have negative exponential relationship whereas halfmaximum linear relationship.