Material composition evaluation of historical Cu alloy aquamanilia by complementary XRF and LIBS measurements

Abstract

Abstract.The material composition of seven historical aquamanilia from museum collections in Kraków and Gdańsk were examined using X-ray fluorescence (XRF) spectrometry and micro-ablation sampling by means of laser-induced breakdown spectroscopy (LIBS) to better understand the materials found in these objects as well as for providing information that can be used towards authentication and dating studies. An additional set of Cu-alloy objects and also a late medieval XV century bronze aquamanile served for reference and comparison. It was found that four of the figures were casted using quaternary and ternary Cu alloys characterized by a Zn content in the range 17.5-23%, admixtures of Sn and Pb below 7%, and presence of impurities like Fe, Ni, Ag, Si, Ba, and Ca. The observed composition similarities were confirmed by statistically processed data. This indicated that the animal figures (lions) are most probably brass replicas of the medieval ones and were produced during the XVIII-XX centuries. In situ measurements were adequate despite inaccuracies associated with signal intensity fluctuations due to surface geometry effects, the presence of patinas, corrosion or contamination, and systematic errors originating from calibration. The proposed complementary approach that uses portable XRF and LIBS instruments ensures consistent data for compositional studies on historical alloys.