The Resistograph as a tool for assessing density profiles of waterlogged archaeological wood

Understanding the degradation profiles of waterlogged archaeological wood (WAW) is essential for effective excavation, conservation, and preservation strategies. This study employed the Resistograph R650-SC (Rinntech, Heidelberg, Germany) to analyse the correlation between drilling resistance and basic density in water saturated wood across various species. Samples from eleven different recent and sound wood species with variable basic density served as samples for calibration between basic density and drilling resistance. Determination of both basic density and drilling resistance in sub-samples of five WAW samples of hard- and softwood with increasing density from surface to core served as test material to verify if resistance profiles can be used to obtain density profiles of waterlogged archaeological wood. The results indicated that while predicted densities based on resistance measurements aligned well with measured densities, individual differences varied significantly. This shows that the Resistograph provides valuable insights into degradation gradients in waterlogged wood, but using single resistance measurements to accurately determine basic densities is not feasible.