Selenium-based black bronze treatment, as compared to other patination technologies of ancient and historic black bronzes

Abstract

Metalworkers have used black patinas on high-status diminutive bronzes in the Mediterranean and Far East beginning in Antiquity. The textual evidence for these bronzes can be ambiguous, but their compositions have been intensively studied and characterized in recent decades. In addition to the ancient technologies, elemental and molecular analysis of black bronzes across millennia and cultures reveals the frequent presence of selenium-based patinas, which we have identified as copper selenite dihydrate. Selenium patination formulations have long been viewed as the 19th century response to the black patinated alloys (such as shakudō and shibuichi) that arrived in Europe from Japan beginning in the Meiji restoration. However, the 19th century European technological literature does not support this, and so selenium-based patination technologies have remained obscure. In this paper, we examine the proliferation of selenium-based technologies in the early 20th century, along with the merits of hypotheses for their origins in patina formulations.