Removing water from wood is a critical requirement for applications in building and construction and for chemical modifications. Normally, green radiata pine (Pinus radiata D. Don) timber, with a moisture content (MC) range at harvest between 150% and 200%, is kiln dried to below fiber saturation point (FSP) to 10–14% MC. In the present work, a physical-chemical-mechanical dewatering process is presented, which involves pressure cycling with supercritical CO2 to remove water to near the FSP. When the CO2 was cycled from ∼4 MPa into the supercritical state, at pressures up to 20 MPa, specimens of cross-sectional dimensions of up to 52 mm were successfully dewatered from a MC of 174%, typical of the green state, to approximately 39% in seven cycles. The specimens with the smallest cross-sectional dimensions dewatered more slowly than the larger specimens. Preheating the green wood before loading it into the dewatering vessel increased the rate of dewatering. The final MCs were similar in all experiments and were independent of specimen dimension (15–52 mm) or preheating temperature between 40°C and 60°C. Pressure-temperature phase diagrams show that it is necessary to compress the CO2 to the supercritical state for efficient dewatering. Diffusion rates and solubility of CO2 in sap were important, but channel opening within specimens was proposed to be a critical factor in the dewatering process. The reason why pressure-based experiments remove water from wood to an MC greater than the established FSP of 30% is not yet clear.

The degree with which wood shrinks and swells with changing moisture content is an important property which determines its suitability for different applications. This property, known as dimensional stability, is often a target property for improvement in wood modification research. Its importance makes it a commonly quantified wood property. Despite this, methods for measuring dimensional stability are not standardised, and there is little consensus on appropriate test methods. Dimensional stability tests can be classified according to the method used to change the moisture content of the wood (liquid water or water vapour) and the duration of the test (until equilibrium is reached, or a shorter duration). Each class of test represents a situation that wood products may encounter in service, and different types of wood (modified or otherwise) may respond differently to each situation. This means that comparative performance between different wood types may be dependent on the test used (and may not be valid for some situations encountered in service). In this paper, standard test methods and methods described in the literature are compared, and recommendations are given for selecting an appropriate dimensional stability test and for minimising sources of bias and measurement uncertainty in the test. It is expected that this will also encourage the adoption of more standardised test methods, enabling comparisons to be made between different studies and different wood types. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Sorption behaviour of radiata pine has been investigated by weighing small specimens continuously during isothermal step changes in relative humidity. The use of wood specimens shorter in the longitudinal direction than the average tracheid length of radiata pine ensures that all tracheids in a specimen are exposed, reducing the effect of wood structure on bound water transport. The small size also allows the specimens to be prepared from a single band of earlywood or latewood.Using the dynamic sorption platform developed at Scion, a number of sorption experiments were undertaken comparing dynamic sorption behaviour of individual bands of earlywood and latewood, which had been heat treated to mimic the chemical changes that occur during high temperature drying.Diffusion coefficients and surface emission coefficients have been calculated from the sorption data, and are presented here. Earlywood and latewood had different sorption behaviour, but no measurable changes in sorption behaviour were seen with the different heat treatments. Diffusion coefficients were strongly dependent on moisture content.