Reassessment of the Penglai III shipwreck and reflections on the wooden artifacts conservation

The conservation of marine archaeological wooden shipwrecks remains a global challenge. The Penglai III shipwreck provides a good case study to examine the state and condition of a wooden shipwreck after nearly 20 years of conservation treatments, especially to assess the effects of PEG hardening treatments and mineral in the wood. Analytical techniques, including ultra-deep far-field 3D microscopy, environmental scanning electron microscopy (ESEM-EDS), micro-Raman spectrometry (Raman), and Fourier transform infrared spectroscopy (FT-IR), were employed. Results indicated that PEG initially aided in drying and strengthening the wood, but prolonged air exposure caused darkening, affecting its visual appearance. This triggered the assessment of the drying and strengthening treatment of wooden shipwrecks and the selection of materials. Wood was rich in iron deposits and calcium deposits, which may lead to acidification and further degradation over time. Environmental control is recommended as a priority for future conservation efforts. This study provides valuable insights into the conservation and restoration of marine wooden shipwrecks.