AIC's 47th Annual Meeting

In the late 19th century and early 20th century, dilute potassium cyanide solution was used as an effective electrolyte for the electrolytic reduction method to treat severely corroded bronze antiquities in Europe. Potassium cyanide reacts quickly with copper element to form copper cyanide and due to its low concentration, this compound is generally not visible to the human eye.  A condition survey at the Buffalo Museum of Science in Buffalo, NY revealed that over one -fifth of the collection exhibited spotty, bright green fluorescence when examined under shortwave ultraviolet radiation (UVC). Notably, this fluorescent material did not glow under longwave ultraviolet radiation (UVA). Solubility tests confirmed that although this material is insoluble in common organic solvents, it can be dissolved with a weak ammonium hydroxide solution (NH4OH). Based on previous research1, these observations indicate the possible presence of copper (I) cyanide. Analysis with Fourier-transform infrared spectroscopy (FTIR) has shown promising, but mixed results; some samples show an obvious cyanide absorption peak around 2250 cm, while some do not. If the presence of copper cyanide can be confirmed, there are several significant implications. Copper cyanide is a toxic compound and therefore any handling of contaminated bronze should be done with extreme caution. In addition, this material can become loose and contaminate nearby storage areas and collections. The discovery that this residue can potentially be detected also offers insight into past preservation practices, how these objects have aged, and the types of potential health hazards they might create. This ongoing research aims to develop an easy detection method for copper cyanide using the combination of short (UVC) and long (UVA) wave ultraviolet radiation.

1. A. Shugar, K. Lough, and J. J. Chen, “Characterization of a Surface Tarnish Found on Daguerreotypes Revealed under Shortwave Ultraviolet Radiation,” Materials Research Society Symposium Proceedings, vol. 1656, 2014.