Impact of Relative Humidity on Wood Sample: A Climate Chamber Experimental Simulation Monitored by Digital...

Area of Science:

• Materials Science
• Environmental Science
• Conservation Science

Background:

• Organic materials undergo continuous equilibrium cycles due to relative humidity (RH) fluctuations.
• Deleterious effects of RH cycles may be mitigated by pre-determining material deformation thresholds.
• Understanding material response to RH is crucial for preventing structural damage to endangered objects.

Purpose of the Study:

• To characterize the behavior of softwood under abrupt RH cycles.
• To identify early signs of structural changes and irreversible damage.
• To lay the groundwork for a preventive model for art objects based on material-specific deformation thresholds.

Main Methods:

• A 1.0 cm thick softwood sample was subjected to abrupt RH cycles.
• Mass and surface displacement rates were continuously monitored.
• Digital holographic speckle-pattern interferometry (DHSPI) measured surface deformation via interference fringes.
• Long-term experiments assessed sample aging.

Main Results:

• Observed hysteresis in the dynamic sorption isotherm.
• A greater rate of surface displacement was recorded during drying phases.
• Long-term monitoring revealed an offset in mass and displacement evolution, indicating wood aging.
• DHSPI provided real-time, high-precision measurement of RH-induced deformation.

Conclusions:

• RH cycles induce measurable mass and displacement changes in softwood.
• Hysteresis and differential drying/wetting rates are key characteristics of wood's response to RH.
• Material-specific deformation thresholds are necessary for predicting and preventing structural damage.
• This research supports the development of proactive conservation strategies for organic cultural heritage.