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CHANGES OF MECHANICAL AND CHEMICAL PROPERTIES OF WOOD
AFTER BROWN-ROT DECAY AND BLUE STAINING
Miha Humar, Bojan Bučar, Viljem Vek,, Franc Pohleven
Department of Wood Science and Technology, Biotechnical faculty, University of Ljubljana, Slovenia
Abstract
Wood inhabiting organisms can cause significant damage on novel and old constructions. Brown rot fungi were
chosen as they are known as the most important decay organisms in historical objects. Blue stain fungi are
frequently present on wood as well, but there is a general opinion that they do not influence mechanical
properties. However, some opposite results have been published as well. Therefore decay patterns of brown rot
and blue stain fungi were investigated using nondestructive mechanical tests, FTIR spectroscopy and colour
measurements. The results showed that blue stain fungi do not cause significant losses in MoE. However,
considerable changes in colour, FTIR spectra and mechanical properties were determined in initial stages of
brown rot decay.
Key words: wood inhabiting fungi, brown rot, blue stain, mechanical properties, FTIR, mass loss
1. Introduction
Norway spruce wood (Picea abies) and Scots pine (Pinus sylvestris) were and still are the most
important wood species for construction applications in Slovenia and most of Central Europe.
Particularly sapwood of those two species is extremely susceptible to colonization by wood inhabiting
fungi [1].
Damage caused by brown rot fungi is the most frequent reason for failure of historical and novel
wooden constructions. Besides wood decay, wooden artifacts are very frequently damaged by blue
stain fungi as well. Among them Aureobasidium pullulans and Sclerophoma pithyophila are reported
as the most important staining organisms [2]. In the previous studies there was a general opinion that
blue-stain fungi do not influence mechanical properties. However, some opposite results have been
published as well [3]. Understanding of decay patterns is of significant importance, to prevent decay
and to develop effective and environmentally acceptable solutions for wood conservation.
There are several methods available for elucidation of decay processes in wood. Among them mass
loss is one of the easiest and frequently used techniques for determination of changes in wood
structure. However, this technique is relatively insensible, as it gives us only rough information on the
processes going on in wood. It is well known, that particularly during initial stages of decay, mass loss
measurements are not the most reliable option. Chemical analysis or mechanical tests are much more
indicative. Some information can be gained from colour as well. In this study, changes in chemical
and mechanical properties of wood exposed to brown rot fungi and blue stain species were
determined.
2. Material and methods
2.1. Sample preparation
Samples (0.5 × 1.0 × 20.0 cm 3 ) were made of Scots pine sapwood (Pinus sylvestris) or Norway spruce
wood (Picea abies). Orientation and quality of the wood met requirements of the standard EN 113 [4].
The samples were exposed to wood inhabiting fungi for the periods between 2 and 8 weeks. Adopted
standard procedure EN 152-1 [5] was used for blue stain exposure and EN 113 [4] for brown rot. In
this experiment, two blue stain (Aureobasidium pullulans and Sclerophoma pithyophila) and two
brown rot fungi (Antrodia vaillantii and Gloeophyllum trabeum) were used.
Joseph Gril (edited by), Wood Science for Conservation of Cultural Heritage –Braga 2008: Proceedings of the International
Conference held by COST Action IE0601 (Braga - Portugal, 5-7 November 2008, ISBN 978-88-6453-157-1 (print)
ISBN 978-88-6453-165-6 (online) © 2010 Firenze University Press