Formation of Black Patina on Bronze Mirrors Caused by Multiphenol

Hot solution of hydroquinone is oxidized by air forming quinone and quinhydrone, both of which have weak oxidizeability, enabling to oxidize metals on the surface of bronze mirror samples forming black and brilliant patina. SEM and electron micro probe analysis show that Cu content is lower than that of the original alloy due to Cu loss; Sn content is higher than the original alloy in patina. This indicates that humic acid is not the substance resulting in making black patina on the bronze mirror surface, but the black patina which produced from hydroquinone solution absence of Si, Al and Mg.