Cocktail therapy for waterlogged archaeological wood: improving the effectiveness of PEG on air-drying by adding APTES and trifluoromethyl phenylboronic acid

Consolidation before dehydration is the major procedure to conserve waterlogged archaeological wood (WAW). Polyethylene glycol (PEG) has been widely used since 1960s. However, if not combined with freeze-drying technique, PEG alone sometimes fails to provide adequate dimensional stability for heavily degraded WAW. A water-solution based ternary formula PAT, standing for PEG, 3-aminopropyltriethoxysilane (APTES) and 4-trifluoromethyl phenylboronic acid (TFMPBA) is studied using WAW of Sapium sp. and Pinus massoniana from the Nanhai No. 1 shipwreck. Compared to 20% PEG treatment, the optimized 20% PAT treatment reduces shrinkage from 71.8% to 51.0% for sapium WAW and from 14.1% to 5.6% for pine WAW after air-drying. Scanning electron microscope and low field nuclear magnetic resonance shows the PAT consolidant preferentially fills the micro cavities in cell walls and changes the drying behavior of PEG treated WAW. Finally, PAT treated samples exhibit lower hygroscopicity than PEG treated one, presumably improving their long-term stability.