Study on the Feasibility of the TG Method for Maximum Water Content Measurement of Waterlogged Archaeological Wood

ABSTRACTThermogravimetry (TG) is used to measure the change of sample mass versus temperature or time under a program controlling temperature. It is a common thermal analysis tool with a precise built-in balance, and accurate data can be obtained through a small amount of sample at the level of milligrams. The feasibility of the TG method for determining maximum water content (MWC) measurement of waterlogged archaeological wood was studied. Simulated waterlogged wood and waterlogged archaeological wood were used to determine the test condition for the TG method. MWC data obtained through the oven-dry and TG methods with different mass gradients from 0–10 mg to >50 mg were analyzed statistically. Deviation, error bar, and coefficient of variation were evaluated. According to the results, when sample mass is no less than 30 mg, and holding time at 105°C is no less than 40 min, data deviation between these two methods is less than 5%. Effect of sampling depth and presence of inorganic deposits were also investigated. Specimens were taken from an archaeological wood with a sampling depth from 2 to 6 mm, then MWC was measured through the TG method. The results indicate MWC of the samples taken from a depth of 2–4 mm is higher than that taken from a depth of 0–2 mm and is lower than that taken from a depth of 4–6 mm, which is related to inorganic deposits. The presence of deposits was verified through SEM-EDX. MWC of three archaeological wood samples from China and five archaeological wood samples from Italy were measured to verify the effectiveness of the TG method when wood species and degradation degree are different.KEYWORDS: ThermogravimetryTGTGAwaterlogged woodarchaeological woodmaximum water contentMWCoven-dry method AcknowledgementsWood samples from the Shell Mount Site, Guye, Gaoming, Guangdong Province were supplied by Professor Yong Cui, Guangdong Provincial Archaeology Institute. Wood samples from Nanhai I Shipwreck were supplied by the Archaeology and Conservation Project of Nanhai I Shipwreck. Wood samples from Italy were supplied by CNR-IBE. The authors thank all of them mentioned above. This work was supported by China National Cultural Heritage Administration under Excellent Young Scientist Fund (2014269); Chinese Academy of Cultural Heritage under Central Public-interest Scientific Institution Basal Research Foundation (2019-JBKY-06), and China’s National Key R&D Program (2020YFC1521800).Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported by China's National Key R&D Program [grant number 2020YFC1521800]; China National Cultural Heritage Administration under Excellent Young Scientist Fund [grant number 2014269]; Chinese Academy of Cultural Heritage under Central Public-interest Scientific Institution Basal Research Foundation [grant number 2019-JBKY-06].