Effect of conservation on radiocarbon ages of wood
Dr Irka Hajdas1, Ms Monika Isler2, PD Dr. Urs Leuzinger3, Ms Roswitha Schweichel3, Dr. Rouven Turck2, Ms Karin Wyss1
1Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland, 2Institute for Archaeology, University of Zurich, Zurich, Switzerland, 3Amt für Archäologie Thurgau, Frauenfeld, Switzerland
Numerous objects of cultural heritage are preserved to prevent their degradation. Conservation treatments are not always well documented and pose a potential obstacle to accurate dating of the material. The resulting offsets in radiocarbon ages cannot always be detected, especially when no information on expected ages and /or alternative dating is available. Most of the conservation materials produced in the 20th and 21st centuries are based on fossil carbon, therefore, they include 14C free components. The problem of an unknown treatment history is the following: the spectrum of conservation materials is wide at the same time the treatment of radiocarbon samples is standardized. Here we present results of various standard treatments applied to well-dated wood, which was preserved with various conservation materials such as polymer Arigal C, Polyethylene glycol (PEG), Ethanol-Ether, and sugar. An offset is observed between the archeological age and the radiocarbon age for most standard cleaning procedures, which highlights the necessity for the identification of the components present in the samples prior to treatment. We present results of infrared spectroscopy obtained on some of the remaining material, which clearly shows the contaminants present in the ‘cleaned’ sample or cellulose. Our results highlight the importance of monitoring the purity of the samples, with the FTIR instrument being an essential part of 14C laboratory equipment.
Irka Hajdas is a geochronologist using radiocarbon dating as a chronometer applied in climate research, environmental studies, archaeology, cultural heritage, and forensics. After completing master studies in nuclear physics at the Jagiellonian University, Cracow, Poland she gained her doctorate from ETH Zurich in 1993 and continued her research at the AMS radiocarbon laboratory at ETH Zurich. Irka is a lecturer at the Geology Department, ETH Zurich. She has authored and co-authored peer-reviewed publications that reflect the interdisciplinary character of the radiocarbon dating method.
Irka Hajdas is a member of the European Geosciences Union and the Anthropocene Working Group.