Water vapor sorption and diffusivity in bark

The interaction of water with archaeological and ethnographic birch bark and its effects on swelling, shrinkage and deformations

“…Different authors [24][25][26][27][28][29] investigated the sorption behaviour of freshly harvested birch bark, mostly in studies on the in uence of the addition of bark material to the properties of wooden particleboards. Samples where the phloem is still attached to the outer bark are characterized by a high hygroscopicity, similar to wood [27], while samples where only the phellem is retained are characterized by a four times smaller moisture content that has little dependency on the speci c birch species.…”

The interaction of water with archeological birch bark and its effects on swelling, shrinking and deformations

“…Different authors [18][19][20][21][22][23] investigated the sorption behavior of freshly harvested birch bark, mostly in studies on the in uence of the addition of bark material to the properties of wooden particleboards.…”

“…Samples where the phloem is still attached to the outer bark are characterized by a high hygroscopicity, similar to wood [21] while samples where only the phellem is retained are characterized by a four times smaller moisture content that has little dependency on the speci c birch specie ( Figure 2). We report here only the adsorption isotherm as the authors reporting desorption results [19] did not let the samples saturate at 100% RH, measuring therefore scanning isotherms whose hysteresis cannot be univocally interpreted [24]. The difference in sorption behavior between samples with or without phloem can be explained by the fact that the secondary phloem is formed structurally by open cells, the sieves tubes, and chemically mostly by polysaccharides that are hygroscopic due to the large number of hydroxyl and carboxyl polar groups that can form hydrogen bonds with water molecules.…”

“…Kajita [23] measured the sorption isotherm at two temperatures, 20°C and 30 °C, and con rmed the wellknown slight decrease of the equilibrium moisture content by increasing temperature observed in hygroscopic materials. Holmberg et al [19] measured scanning isotherms in absorption and desorption for Betula Papyrifera samples. The time needed to reach equilibrium at each step of the sorption isotherm depends on the sample thickness, preparation method and presence of ventilation in the surrounding environment.…”

“…The time needed to reach equilibrium at each step of the sorption isotherm depends on the sample thickness, preparation method and presence of ventilation in the surrounding environment. Holmberg et al [19] showed that for cuboid samples of 3 mm side in a ventilated environment it is of the order of 8 hours where half of the weight loss is attained in the rst 30 minutes.…”