The objective of the present study was to investigate the interaction between Cu-containing
preservatives and birch (Betula spp.) and pine (Pinus sylvestris L.) wood, modified at a relatively mild
temperatures (150 – 180ºC). The disposition of wood to absorb water was evaluated by capillary absorption
(CA) tests through the specimens’ tangential and radial surface. Changes in wood drying characteristics due
to thermal modification (TM) were evaluated by monitoring wood moisture dynamics after impregnation. In
order to assess the capacity of wood to absorb preservatives, a vacuum/pressure process was used to
impregnate small specimens for which uniform saturation into the entire volume can easily be reached.
Quantitative determination of copper Cu content in the specimens was performed by using atomic absorption
spectroscopy (AAS). The fixation of the absorbed Cu was evaluated by subjecting the specimens to leaching
procedures according to EN 84 and assessing the ratio of retained Cu in the specimens. The CA test
showed deceleration of capillary absorption in TM birch wood through both surfaces, with similar absorption
rates regardless of treatment temperatures. A significant increase in the absorption rate through the
tangential surface was recorded for TM pine wood and the increase was greater for specimens treated at
higher temperatures. The results of moisture content monitoring showed a similar reduction in the drying rate
due to thermal modification regardless of species. Comparing wood of one species with similar densities,
less preservative was absorbed by TM wood. However, the results of AAS showed that, in comparison with
unmodified wood, 10% (birch) and 25% (pine) more Cu per one gram of wood was introduced during
impregnation. Nevertheless, TM also resulted in higher Cu leaching rates for both species