Physical Properties of Nearly Thousand-Year-Old Oak Wood Compared with Oak Wood of Different Origins from Previous Centuries and Present Times

The aim of the study was to assess the hardness and compressive strength of oak wood from various historical contexts, and to compare these properties with modern oak wood. The study utilized both radiocarbon and dendrochronological dating to determine the age of the wood. A total of five oak wood fragments analyzed i.e. bog oak, oak wood from the bell tower of the Collegiate Basilica of the Holy Spirit in Przeworsk; oak wood from the scaffolding of the St. Nicholas Church in Gniew, wood from a dismantled granary in Drawsko Pomorskie and sample from a water dam in Czaniec. The dating confirmed that the oak fragments varied in age, ranging from several centuries to over 900 years. The mechanical tests using the Brinell method and compressive strength tests indicated that wood of bog oak displayed statistically significant differences in compressive strength compared to the other wood samples, which could be attributed to the long-term mineral saturation of the wood from prolonged exposure to anaerobic conditions in the bog. This mineralization likely caused a reduction in its elasticity and overall strength. In contrast, other samples, which had been exposed to varying environmental conditions like periodic water immersion or protection from moisture, did not show significant differences in mechanical tests. Despite these challenges, the findings suggest that compressive strength could serve as a useful indicator for estimating the age of oak wood in archaeological contexts, particularly for assessing the influence of long-term environmental conditions on wood properties.