ON YELLOW DISCOLORATIONS WHEN DRYING OAK, QUERCUS ROBUR

• Growing trees many times contain more water than wood. When wood is to be utilized in the form of furniture it must therefore be dried in a kiln-dryer. In such a dryer the climate is very humid and warm which is ideal for many microorganisms such as bacteria and fungi. During their metabolism they change the chemical environment which sometimes lead to undisireable effects such as discolorations. In this paper we have examined specimen from oak, Quercus robur, collected from some parquet floor factories in Sweden. During drying some of these wood battens were affected with yellow streaks and spots which made the wood impossible to use for flooring. By examining small samples of the battens in light, as well as in scanning electron microscopes, we found that fungi grew inside the wooden tissue. By cultivation on agar plates we found several species where one has been identified as Penicillium roqueforti and another one as Paecilomyces variotii. We have also found that these fungi are extremely sensitive to high pH-values, so by spraying the wood with solutions of high pH already in the sawmill will probably make this problem much smaller.

Nyckelord

discolouration

oak

fungi

identification

staining properties

TECHNOLOGY

TEKNIKVETENSKAP

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