Change of Wood Moisture Content During Artificial Light Irradiation and its Influence on Colour Measurement

Baar, Jan; Ondroušková, Jitka; Rademacher, Peter

doi:10.5552/drind.2015.1430

Cited by 1 publication

(1 citation statement)

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“…The presence of bonded water in porous cell walls, particularly with capillary condensed water, may alter the optical appearance of wood. During artificial weathering, the MC may vary distinctively, especially during long-term exposure (Baar et al 2015). This means that wood samples need to be properly conditioned prior and during exposure in case individual color measurements are carried out to obtain comparable measurement conditions.…”

Section: Introductionmentioning

confidence: 99%

Color Changes of Various Wood Species in Response to Moisture

Baar¹,

Paschová²,

Čermák³

et al. 2019

WFS

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Color including texture and gloss is one of the most important esthetical attributes of wood. For any porous materials in contact with water, the phenomenon of surface darkening arises from a change in the refractive index, as water enters air-filled pores. For the first time, this research investigated to what extent MC differences affect the surface color, below fiber saturation and after the pores are filled with water, with respect to extractive contents. Samples from 13 wood species were exposed to various climates, and as soon as EMC was reached, the color was determined. Color changes were also recorded after water submersion and also after vacuum impregnation in water. Chromaticity parameters a* and b* widely increased, along with higher moisture contents. Lightness changes were mostly stable at lower moisture contents. An exception was demonstrated by the heartwood species black locust, plum, walnut, and oak, which showed a brightening effect at lower moisture contents, followed by the darkening phase. The overall darkening of wood at high RH is connected to capillary condensation. Liquid water present in the cell lumen most caused darkening and an intensification of hue (increase in a* and b*). Darkening was even more expressed after vacuum impregnation with water. In conclusion, with only limited fluctuations in moisture contents below fiber saturation, the expected color changes are minor to neglectable.

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Section: Introductionmentioning

confidence: 99%