Archaeological wood is a kind of ‘new material’ that has deteriorated due to long-term degradation. The existing wood science theory and evaluation methods are not fully applicable to archaeological wood. Moreover, current physical-mechanical evaluation methods are inadequate for fragile archaeological wood due to their insufficient accuracy and the large sample amount required, causing difficulties in many necessary physical-mechanical repeatability tests. In light of these limitations, the representative samples on Nanhai No. 1, a merchant shipwreck in the Song Dynasty, were selected as the research objects in this paper. The shipwreck is a typical waterlogged wooden artifact. A quasi-nondestructive physical-mechanical evaluation technique for archaeological wood was developed with the thermomechanical analyzer (TMA). This study used TMA to evaluate the bending strength of representative waterlogged archaeological samples of Nanhai No. 1 shipwreck and sound wood with the same species. Besides, the thermal linear expansion coefficients in the ambient temperature range were obtained. The sizes of the samples used in the tests were only 2 mm × 8 mm × 0.3 mm and 1 cm × 1 cm × 1 cm, respectively. Bending strength results of archaeological wood by the TMA method conformed to the tendency that the bending strength decreases with the increase of decay degree. In addition, the longitudinal linear expansion coefficients of archaeological wood reached 80%–115% of those in the transverse grain direction, which were about 10 times higher than those of the sound wood. The linear expansion coefficients of archaeological wood in three directions were similar. Based on the results of Fourier transform infrared analysis (FT-IR), the significant differences in the physical-mechanical properties of the archaeological wood and the sound wood were induced to be mainly ascribed to the decomposition and the loss of hemicellulose in the archaeological wood. The cell wall substrate could not stabilize the cellulose skeleton, which led to the instability of the tracheid structure of the archaeological wood. This study provided a proven quasi-nondestructive method for the preservation state evaluation of waterlogged archaeological wood (WAW) from the Nanhai I shipwreck and other similar waterlogged wooden relics.

A greater understanding of moisture sorption behaviour of aged wooden structural components, which has a close relationship with dimensional stability, is required to effectively evaluate and preserve historical artefacts. This study focused on the effects of aging on Baotou beam samples from a Chinese historical wooden building. An analysis of the sorption isotherms and hysteresis loops of a naturally aged, decayed sample (AOS), an aged sound sample (AIS), and a reference sample (RS), using classical sorption isotherm models revealed that the moisture sorption behaviour of samples from the same growth ring in a Baotou beam can differ significantly. AOS showed higher hygroscopicity than AIS, and both these samples were more hygroscopic than RS. Furthermore, the mono/multilayer moisture contents of AOS were always higher than those of AIS and RS. In addition, Fourier transform infrared, second-derivative infrared, and two-dimensional correlation infrared spectroscopy were used to investigate chemical changes in the samples. The relative hemicellulose and lignin contents of the samples changed significantly with wood aging. Furthermore, AOS exhibited the highest calcium oxalate content, which may be associated with fungal infections. Overall, these results provide valuable insights into the effects of aging on wood samples and the dimensional stability of timber structures, which could inform future research on methods for the preservation or restoration of aging timber structures.

Studying waterlogged archaeological wood moisture characteristics can provide strong support for the safe dehydration and preservation of waterlogged wooden artifacts. Herein, six waterlogged archaeological wood samples with moisture contents of 154%–968% chosen from two ancient Chinese shipwrecks, Nanhai No. 1 and Changjiangkou No. 2, and six non-degraded modern wood samples of the relevant corresponding species were selected to study the moisture characteristics by low-temperature nuclear magnetic resonance (NMR) and the dynamic sorption of water vapor (DVS). It was found that the six waterlogged archaeological wood samples exhibited three deterioration states: slightly, moderately, and seriously deteriorated. Wood deterioration caused significantly increased fiber saturation point (FSP) values for waterlogged archaeological wood. This is mainly owing to changes in the pore size distribution of cell walls. Moreover, NMR is more accurate than DVS in obtaining FSP for severely degraded samples. Additionally, moisture content was positively associated with wood deterioration. Maximum water content (MWC), free water content, and bound water content exhibited an exponential relationship with the basic density (BD). The contribution of bound water in waterlogged archaeological wood was less than that of modern wood and decreased with deterioration.

Waterlogged archaeological wood samples may degrade during long-term immersion in microbial-activity environments, which causes its biodegradation. Simultaneous dynamic vapor sorption (SDVS) and two-dimensional correlation infrared (2D COS-IR) spectroscopy reveal the degradation inhomogeneity of waterlogged fir wood from the Shengbeiyu shipwreck. The waterlogged and reference wood exhibit type II sorption isotherms. The equilibrium moisture contents of waterlogged archaeological fir wood from a decay region (WFD) were 22.5% higher than those of waterlogged archaeological fir wood from a sound region (WFS). WFD exhibits a higher measurable sorption hysteresis than WFS, implying greater variation in the surface moisture content in the WFD region compared to the WFS region, which may compromise the dimensional stability of the shipwreck. 2D COS-IR spectra confirmed the inhomogeneous degradation of the waterlogged wood via numerous mechanisms. The efficacy of SDVS and 2D COS-IR spectroscopy in the evaluation of the degradation state of waterlogged wood was demonstrated. This study verifies the existence of hygroscopic and chemical differences between visually similar samples from the same shipwreck.

The goal of this research was to analyze the fungal community responsible for the biodeterioration of a pirogue in the National Maritime Museum of China and to make recommendations for the protection of this artifact. Molecular identification of fungal strains isolated from the surface of the pirogue and the air of the storage room that were most closely related to Cladosporium, Penicillium, Talaromyces and Trichoderma spp. DNA extracted from the samples was sequenced on the Illumina MiSeq platform. The results showed that the predominant fungal genera present were Penicillium sp., Cladosporium sp. and Exophiala sp. Thereafter, cellulose degradation experiments were carried out on the predominant fungi screened by pure culturing. Finally, we tested the sensitivity of the predominant fungal isolates to four biocides. This work suggests that we should pay more attention to Penicillium sp. and Cladosporium sp. in the protection of wooden artifacts, and environmental control is recommended as the main means of protecting the pirogue.

The significance of waterlogged archaeological wood (WAW) lies in its profound informational value, encompassing historical, cultural, artistic, and scientific aspects of human civilization, and therefore need to be properly studied and preserved. In this study, the utilization of near-infrared (NIR) spectroscopy is employed as a predictive tool for assessing the hardness value of WAW. Given the submerged burial conditions, waterlogged wooden heritage frequently undergo substantial degradation in their physical and mechanical properties. The mechanical properties of waterlogged wooden heritage are essential for evaluating their state of preservation and devising appropriate conservation and restoration strategies. However, conventional methods for testing mechanical properties are limited by factors such as the availability of adequate sample size and quantity, adherence to the “principle of minimum intervention,” and cost considerations. NIR spectroscopy is a non-destructive, rapid, sensitive, and low-cost analytical technique with great potential for application in this area. In this study, two large and significant ancient Chinese shipwrecks were investigated. One hundred ninety-seven samples were collected and analyzed using NIR spectroscopy and a portable C-type shore hardness testing method. A partial least squares (PLS) regression model was developed to predict the hardness of the WAW. The model was optimized and validated using different preprocessing methods and spectral ranges. The results indicate that the best models were obtained with first derivatives + multiple scattering corrections (MSC) and first derivatives + standard normal variate (SNV) preprocessing in the 1000–2100 nm spectral range, both with an R ² _c of 0.97, a root mean squared error of correction (RMSEC) of 2.39 and 2.40, and a standard error of correction (SEC) of 2.40 and 2.41. Furthermore, they exhibited an R ² _v of 0.89 and 0.87, a root mean squared error of cross-validation (RMSECV) of 4.43 and 4.67, a standard error of cross-validation (SECV) of 4.45 and 4.68, and RPD values of 3.02 and 2.88, respectively. A coefficient of determination of the established prediction model (R ² _p) of 0.89 with a relative standard deviation for prediction (RSD) of 6.9% < 10% was obtained using a sample from the prediction set to predict the established model inversely. These results demonstrate that NIR spectroscopy could enable a rapid, non-destructive, and accurate estimation of the hardness of WAW. Moreover, by carefully choosing appropriate preprocessing techniques and spectral ranges, the predictive capabilities and accuracy of the model can be further enhanced. This research also contributes to the development of a theoretical framework and a methodological approach for future studies in this field. Furthermore, the data obtained from this study are crucial for determining effective preservation strategies for waterlogged archaeological wood.