Mats Rundgren

Polyethylene glycol (PEG) is commonly used in the conservation of wooden artifacts, but its presence adversely affects the accuracy of radiocarbon dating. It is therefore critical to have robust methods for the removal of PEG from heritage materials. This paper presents the results of an experiment designed to test a protocol for the removal of low molecular-weight PEG-400 from conserved wood. We conducted a known-age test using PEG-400 impregnated materials from the excavation of the medieval royal shipwreck, Gribshunden, built in 1484 CE and sunk in 1495 CE. We test our results by using matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) to show that no PEG is detectable in our samples after a three-step pretreatment protocol. Furthermore, radiocarbon dates of our pretreated samples returned dates that match the known age of the wood. Our results indicate that our pretreatment protocol can be used to successfully remove PEG-400 from conserved wood, allowing for accurate 14C dating.