Water vapor sorption in a dried red oak lumber package stored in a high humidity environment

Water vapor sorption in a commercial dimensional dried lumber package has never been investigated although sorption equilibria and rate were studied for wood samples. In this research, a wireless probe system is used to monitor moisture content (MC) change for representative thirty nine positions of dried red oak lumber package. End coating was applied to both ends of each board prior to drying to 7% MC, but was removed from one end for this experiment to study the effect of end-coating. The environmental chamber which held the package was set to temperature 21.1°C and relative humidity 80%. The distribution of moisture content of the package over 19 weeks was obtained and a mathematic model was developed to predict moisture gain over time. The results show that sorption process is controlled not only by Fick\u27s law, but also by swelling stress relaxation. Stepwise function and fluctuation phenomenon from the experiment results are also explained by a new concept---gas creeping motion