TY - JOUR

T1 - Artifacts in electrical measurements on wood caused by non-uniform moisture distributions

AU - Fredriksson, Maria

AU - Thybring, Emil Engelund

AU - Zelinka, Samuel L.

PY - 2021

Y1 - 2021

N2 - This paper examines how the moisture conditioning method affects the electrical conductance of wood. A widely used dataset was acquired by Stamm in 1929 who used a method of conditioning where water-saturated wood specimens were partially dried, sealed and left for a period of time for moisture to be redistributed before the electrical conductance was measured. However, more recent measurements combined conditioning above saturated salt solutions and pressure plate/pressure membrane techniques to obtain equilibrium moisture contents at constant relative humidity levels in the full moisture range. In this paper, the electrical conductance as a function of moisture content was compared for these two conditioning methods. When the specimens were conditioned to constant relative humidity levels, the data obeyed a percolation model better than when the conditioning procedure by Stamm was used. This was attributed to that Stamm's method gives moisture gradients through the specimen because of sorption hysteresis effects, even though the wood is conditioned to a steady-state moisture content. Equilibration to constant relative humidity levels thus provided more well-defined moisture states and that the data followed a percolation model indicates that the mechanism of electrical conduction in wood does not change, even at high moisture contents.

AB - This paper examines how the moisture conditioning method affects the electrical conductance of wood. A widely used dataset was acquired by Stamm in 1929 who used a method of conditioning where water-saturated wood specimens were partially dried, sealed and left for a period of time for moisture to be redistributed before the electrical conductance was measured. However, more recent measurements combined conditioning above saturated salt solutions and pressure plate/pressure membrane techniques to obtain equilibrium moisture contents at constant relative humidity levels in the full moisture range. In this paper, the electrical conductance as a function of moisture content was compared for these two conditioning methods. When the specimens were conditioned to constant relative humidity levels, the data obeyed a percolation model better than when the conditioning procedure by Stamm was used. This was attributed to that Stamm's method gives moisture gradients through the specimen because of sorption hysteresis effects, even though the wood is conditioned to a steady-state moisture content. Equilibration to constant relative humidity levels thus provided more well-defined moisture states and that the data followed a percolation model indicates that the mechanism of electrical conduction in wood does not change, even at high moisture contents.

KW - electrical conduction

KW - ionic conduction

KW - moisture content

KW - percolation theory

KW - wood

U2 - 10.1515/hf-2020-0138

DO - 10.1515/hf-2020-0138

M3 - Journal article

AN - SCOPUS:85095953278

VL - 75

SP - 517

EP - 525

JO - Holzforschung

JF - Holzforschung

SN - 0018-3830

IS - 6

ER -