Investigations on chemical changes of surface contact-charred Norway spruce (Picea abies L.) using ATR-FTIR spectroscopy and pH value measurements

To obtain more information on possible reasons for the increased durability of surface charred wood, the chemical changes of surface contact-charred Norway spruce (Picea abies L.) were investigated by ATR-FTIR spectroscopy and pH value measurements. Temperatures of 300 °C, 350 °C and 400 °C were used to carbonize the surfaces of specimens for a duration of ≈ 3 min per surface. Measurements were conducted not only on the surface of the specimens but also on areas underneath the surface by removing material in steps. By that a “depth profile” of chemical changes could be created. Overall, the results of the applied methods seem to confirm the literature regarding the occurrence of different temperature zones in areas below the surface where different chemical changes occur. Concerning possible reasons for the increase in durability of charred wood, the formation of phenolic compounds during pyrolysis could be determined.