The brass censer was covered in mercury gilding, the most common gilding technique in medieval goldsmithing. An amalgam of gold and mercury is applied over the entire surface of the object. It is then heated so that the mercury evaporates and the gold adheres to the metal surface. This is followed by a finishing process of burnishing or polishing: unlike polishing, which produces a smooth, shiny appearance, burnishing, through rubbing and hammering, produces an irregular effect.