Mold Growth on Sapwood Boards Exposed Outdoors: The Impact of Wood Drying

Abstract

Mold growth on dried Norway spruce and Scots pine sapwood boards was investigated in an accelerated outdoor field test for 96 days. The boards were dried using three different methods of stacking: single stacking, double stacking with the sapwood sides in each pair facing toward each other, and double stacking with sapwood sides facing outward. Drying was performed at three temperatures: 25°C, corresponding to air drying, and kiln drying at 70°C and 110°C. The degree of mold growth was visually assessed on both sides of each board. On average, pine boards showed a higher level of mold growth than the spruce boards. The highest average level of mold growth was found on the boards kiln dried at 70°C, whereas the air-dried boards and the boards kiln dried at 110°C showed considerably less mold growth. Stacking the boards during drying had a large impact on mold susceptibility of the sapwood. This study confirmed that, during the drying process, it is possible to direct the migration of nutrients in sapwood toward one chosen side of each board by double stacking; the opposite side leaches out, which has a great impact on surface mold growth. Chemical analyses of monosaccharide sugar gradients beneath the boards' surfaces confirmed the results.

Anatomical, Physical, Chemical, and Biological Durability Properties of Two Rattan Species of Different Diameter Classes

“…Both flat surfaces of the samples were evaluated visually and graded on a scale of 0 (no infestation) to 6 (extremely heavy infestation). More about the grading and method can be found in Sehlstedt-Persson et al [25].…”

Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally modified European aspen and downy birch wood

“…After a 21-day incubation period, the experiment was stopped due to abundant mold growth on some of the sample surfaces. Both flat surfaces of each sample were evaluated and graded (on a 0-6 scale) by a method described in a previous study [21]. Two people performed the visual inspection excluding the edges and heartwood areas.…”

Heat Treatments of High Temperature Dried Norway Spruce Boards: Saccharides and Furfurals in Sapwood Surfaces

“…Increasing temperatures during the industrial drying of wood has been a trend during several decades, resulting in a more efficient production and controlled properties of wooden boards. However, modern drying schedules also accelerate the migration of soluble sugars to the wood surface (Terziev et al 1993;McCurdy 2005) where they could increase the ability for growth of mould (Theander et al 1993;Sehlstedt-Persson 2011). This issue has become more important with a warmer climate and use of more energy efficient houses.…”