The physical interactions of the wood-water-formaldehyde system are reviewed.Swelling data at 20 and 40 C (68 and 104 F) are presented which show that Douglas-fir and red alder wood shrink relative to pure water in low concentration water-formaldehyde solutions, and swell in higher concentration solutions ultimately to 18% by volume for a 24% (weight) solution of formaldehyde at 40 C (104 F).The composite sorption isotherms of the wood-water-formaldehyde system are complex. There is seen, however, an initial relative increase in water concentration of the sorbed phase, followed by a general decrease of water concentration for most of the other concentrations studied. The reasons for this are not known
