- Duc-Thanh Nguyen, Research Institute of Forest Industry, Vietnamese Academy of Forest Sciences

- Duy-Ngoc Bui (buiduyngocfsiv@gmail.com), Research Institute of Forest Industry, Vietnamese Academy of Forest Sciences

- Trung-Hieu Hoang (hieuhoangtrungbqls@gmail.com),Research Institute of Forest Industry, Vietnamese Academy of Forest Sciences

The paper shows the conservation results of ten archaeological waterlogged woods (WLW) treated with polyethylene glycol (PEG). The WLW samples were collected from the Thang Long Imperial Citadel excavation site in Hanoi, Vietnam, which is a member of the UNESCO World Heritage. The impregnation process was the first conducted with low molecular weigh PEG 2000 then with high molecular weight PEG 4000. The results showed that the dimensional stability of WLWs significantly improved after the PEG treatments. The anti-shrink efficiency (ASE) values of the WLWs treated with final PEG concentration of 40% ranged between 72.5% and 96.2% depending on the species and degree of wood degradation. These values varied from 82.4% to 96.9% for the WLWs treated with 70% PEG. Observations on the microscopic cellular structure of wood showed that PEG primarily filled the wood voids, thus treated woods maintained their original cell structures, forms, and shapes. Based on results obtained from the study, two-step treatment using PEG 2000 and PEG 4000 can be used for conservation of WLWs unearthed at Thang Long Imperial Citadel site.