Monitoring Dynamic Moisture Gradients in Wood using Inserted Relative Humidity and Temperature Sensors

To be able to combine the preservation of wooden objects of culturalsignificance with energy efficiency measures it is important to developour knowledge of the relation between the rate of change of relativehumidity and temperature, moisture content gradients and the resultingdimensional change of wood. The work presented here introduces andevaluates a method for monitoring dynamic moisture content gradients,mainly for research applications. Relative humidity and temperaturewere measured by miniature sensors, placed in drilled holes at differentdepths in wood samples to monitor the moisture transport. The data wasused to calculate moisture content and the results could hence be comparedwith the results from a commercial resistance moisture meter,monitored at the same depths. The results of the two methods did notcoincide. A Fickian model for moisture diffusion was chosen to verify themonitored results. It showed poor fit with the commercial resistancemethod and a reasonably good fit with the new method using relativehumidity and temperature sensors. We concluded that the new methodprovides reliable and consistent data suitable for monitoring moisturecontent at different depths under unsteady state conditions, while thedata generated by the resistance method in our set-up was inconsistentwith the model and with our understanding of the moisture transportprocess