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On the changes of natural durability of wood sterilised by gamma radiation
2006 - IRG/WP 06-10571
The preliminary study data of natural durability of wood in lab conditions against rot fungi dependency on different sterilisation method have been presented. In the research, white rot fungus Schizophyllum commune Fr.: Fr. and brown rot fungus Poria placenta (Fries) Coke sensu J. Erikson. on the Scots pine were tested. Cobalt 60Co was used as a gamma radiation source at the dosage of 30 kGy. Control non-irradiated samples were sterilised by autoclaving (123 °C, 1,8 bar for 30 min). After 4 weeks of exposure to fungus S. commune statistically significant difference in mass loss between gamma irradiated and autoclaved samples have been established. Irradiated samples had greater mass loss. During exposure, the difference decreased and became less significant. At the end of exposure, after 16 weeks, no significant difference was determined. On the other hand, after 4 weeks of exposure to fungus P. placenta there was no significant difference in mass loss between irradiated and autoclaved samples. During exposure difference in mass loss between autoclaved and irradiated wood became more and more significant.
R Despot, M Hasan, M Glavaš, G Rep


The effect of gamma radiation on selected wood properties
2008 - IRG/WP 08-40394
As an easy, fast, and effective sterilisation method, gamma irradiation changes molecular structures not only in pest’s living cells, but also in wooden cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness. The influence of gamma radiation concerning total amount of water-soluble carbohydrates (TSC), maximum swelling (aMAX) and resistance to impact milling (RIM) were investigated. Cobalt (60Co) was used as gamma source and Scots pine sapwood (Pinus sylvestris L.) was irradiated with dosages of 30, 90 and 150 kGy. A strong linear correlation between TSC and the radiation dosage was found. Leached irradiated specimens had significantly greater TSC than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters was improved. Gamma radiation had no significant effect on aMAX and the elapsed time after irradiation did not influence aMAX, RIM, and TSC.
R Despot, M Hasan, A O Rapp, C Brischke, C R Welzbacher


The evaluation of permethrin for wood preservation
1977 - IRG/WP 3107
The toxicity of the synthetic pyrethroid permethrin (NRDC 143) to a range of wood destroying insects has been investigated. In tests using Hylotrupes bajulus, Anobium punctatum, Lyctus brunneus and Reticulitermes santonensis permethrin showed a similar order of toxicity to that of gamma-BHC. Although the toxicity of permethrin to adult Anobium punctatum was of the same order as that of gamma-BHC, the toxicity to larvae was rather lower. The implications of these results are discussed and it is concluded that, subject to further field evaluation, permethrin could provide an alternative to gamma-BHC and dieldrin in wood preservatives.
R W Berry


Microscopic characteristics of Pinus radiata wood veneers weathered outdoors for one yea
1993 - IRG/WP 93-10018
Radiata pine (Pinus radiata) wood veneers glued to solid wood hacking strips were exposed outdoors at 45° north-facing for one year and then examined by light microscopy (LM) and transmission electron microscopy (TEM). As expected, the exposed wood surfaces were colonised by a variety of microorganisms; however, wood decay was not observed. Ultlaviolet (UV light) radiation and water were the main factors responsible for changes such as discolouration and the altered microstructure of wood cell walls which led to their disintegration. Cell wall discolouration observed under LM is due to UV light-induced breakdown in lignin, which may eventually disappear completely from some areas of the wood cell wall. The resulting increase in cell wall porosity was observable in the TEM. TEM was also used to identify the cause of failure of an oil-baised stain which was applied to one set of veneers before exposing them outdoors. The observations underscore the potential udefulness of a combined light and electron microscopy approach to study wood weathering.
A P Singh, R A B Sweeney, E A Dunningham, D V Plackett


Influence of storage on mould susceptibility of wood at relative humidity values lower than 100%
1989 - IRG/WP 1413
It is well known that wood material changes with time because of different environmental influences. The effects of such changes on the subsequent mould susceptibility are less known. In this paper we report on increased mould susceptibility of pine wood after storage. Mould growth was detected by indirect methods.
J Bjurman


The permanence of permethrin in wood preservation
1984 - IRG/WP 3288
The permanence of the synthetic pyrethroid permethrin in treated wood has been assessed for double vacuum and immersion treated Scots pine sapwood and whitewood using a 0.5% m/m solution of the insecticide in a hydrocarbon solvent. It is concluded that for all but the outermost 0.5 mm of the treated battens the distribution of the permethrin is relatively permanent. The outermost 0.5 mm appears vulnerable to degradation rather than volatile loss, and this varies with timber species and the loading in that zone. Linking this information with published bioassay work allows speculation as to the strength of treating solutions needed for adequate long-term protection
R J Orsler, M W S Stone


Acceleration of the fixation of chromated wood preservatives by UV-radiation
1989 - IRG/WP 3544
Preliminary laboratory tests demonstrated that the fixation of chromated water-borne wood preservatives may be accelerated by UV-radiation. The degree of fixation depends on the intensity of radiation and the prevailing temperature. Three hours radiation at 20°C in a device for artificial weathering diminished the leaching of chromium to 43% and of copper to 23% compared to not-radiated samples. Two hours radiation at 60°C gave almost complete fixation. Five to seven seconds radiation in a high energetic commercial plant for hardening of paints diminished the leaching of chromium to 75% and of copper to 30% and a second radiation of the same samples still increased the fixation. Further tests are necessary to obtain more details on the use of UV-radiation for fixation in practice.
H M Illner, H Willeitner, K Brandt


Volatile losses of wood preservatives
1973 - IRG/WP 236
The purpose of the work we have undertaken so far has been to try to quantify the volatile losses which occur in treated timber, and to examine some of the factors which influence these losses. The preservative compound chosen for the initial part of the programme was the contact insecticide g-BHC. This was attractive for several reasons, not the least of which was that specific and sensitive analysis was possible using gas-liquid chromatography. In addition to this, g-BHC is of major importance in insect control in both pre-treatment and remedial treatment, the latter frequently being subject to a written guarantee.
J W W Morgan, D F Purslow


Effect of angle of exposure on degradation of radiata pine during weathering trials
1988 - IRG/WP 2301
The importance of angle of exposure on the degree of weathering of materials has not been adequately resolved. In conventional tests, specimens are exposed at an angle of 45° facing the equator, but more recently experiments on polymeric materials have suggested that an angle of 0° may be preferable since this angle maximises levels of received ultra-violet radiation. In this paper the degradation of Radiata pine (Pinus radiata D. Don) during weathering was assessed at 5 angles of exposure (0°, 45°, 60°, 70°, 90°) over 50 days by measuring changes in weight and chemical composition. In order to confirm previous observations measurements of received ultra-violet radiation (< 320 nm) at these angles of exposure were also made using polysulphone polymer film dosimeters. Roth weight loss and chemical data indicate that degradation of Radiata pine during weathering was negatively correlated (p < 0.001) with increasing angle of exposure. The implications of these findings for the conduct of weathering trials are discussed.
P D Evans


Experiments in accelerated ageing
1984 - IRG/WP 2223
Experiments using a vacuum oven to accelerate the evaporative loss of g-HCH from treated wood blocks have indicated that the method described in this paper has the potential to reproduce in a relatively short time the distributions and loadings of the insecticide that are found during natural ageing. By contrast, the wind tunnel removed the volatile material in a way not found in natural ageing and characterised principally by the rapid removal of material close to or on the wood surface. Theoretical considerations reinforced these practical observations indicating that the vacuum oven could provide a much quicker means of attaining the condition that is likely to exist in aged timber.
R J Orsler, M W S Stone


The detection of organic solvent preservatives in wood by thin-layer chromatography
1975 - IRG/WP 357
A simple and rapid method for the detection of common organic solvent wood preservative materials is described. The method uses thin-layer chromatography after leaching of the preservative from sections of timber with chloroform. RF values and the sensitivity of the method are discussed and a routine procedure for identification of the organic and organometallic preservatives is proposed. Methods of achieving greater sensitivity for particular applications are also described.
B G Henshaw, J W W Morgan, N Williams


Statement on laws relating to wood preservation in Brazil
1977 - IRG/WP 399
A set of copies of the laws relating to wood preservation in Brazil (in Portuguese) have been deposited with the IRG Secretariat. Generally speaking, it can be said that all public constructions have to comply with the laws that have been laid down. All organisations (governmental and private) which produce or apply wood preservatives are registered. The private sector is not obliged to abide by these regulations. Pentachlorophenol is still the dominant preservative in the south of the country. Poles are treated with the usual water-soluble salts. Sleepers are impregnated with local creosote. To my knowledge, there are no real restrictions on the use of specific wood preservatives, apart from g-HCH (gamma-hexacyclohexane) which is forbidden to be used.
P Karstedt


The influence of UV and IR radiation on leaching of copper and chromium from preservative-treated pine and spruce
1992 - IRG/WP 92-3687
The influence of artifical UV- and IR-radiation on the leaching of copper and chromium components of a CCB-preservative from freshly treated pine and spruce was evaluated. On small pinewood samples it could be shown, that the leaching of copper and chromium can considerabely be reduced by UV-radiation. A Philips HPA lamp type reduced the leaching most effective. IR-radiation lead to higher leaching. Leaching decreased with a higher intensity of radiation and a longer duration. Experiments with larger specimens showed, that a reduction in leaching of copper and chromium of ca. 70% can be reached with a 60 sec. radiation.
H Militz


The characteristics of biodegradation mechanism of gamma-irradiated wood
2007 - IRG/WP 07-20352
Gamma radiation, as an easy, fast and effective sterilisation method, changes molecular structure in pest’s living cells, but also in wooden cell walls. Radiation-induced depolymerisation causes significant changes in wood properties crucial for laboratory testing of wood-preservative effectiveness. Natural durability of wood against rot fungi in lab conditions dependency on different sterilisation method was researched and the data presented. In the research, white rot fungus Trametes versicolor (L.: Fr.) Pilat. and brown rot fungus Gloeophyllum trabeum (Pers.: Fr.) were tested on the Scots pine. Cobalt 60Co was used as a gamma radiation source at the dosage of 30 kGy. Control non-irradiated specimens were sterilised by autoclaving. Statistically significant differences in mass loss between gamma irradiated and autoclaved specimens have been established after 8 weeks of exposure to fungus G. trabeum. Irradiated specimens had greater mass loss. During further exposure, the differences decreased and became insignificant. On the other hand, during all time of exposure to fungus T. versicolor, no significant differences in mass loss between irradiated and autoclaved specimens were determined.
R Despot, M Hasan, F Pohleven, M Humar, G Rep


The Effect of Solar Radiation on the Surface Checking of Wood
2007 - IRG/WP 07-40356
The aim of this research was to investigate whether exposure to solar radiation increases the checking of wood exposed to the weather, and examine the causes and spectral dependency of such an effect. Lodgepole pine samples were exposed outdoors under filters which transmitted selected regions of the solar spectrum while allowing other weathering factors to act on samples. Surface checking in samples was quantified after 12, 24 and 36 weeks, and the structural changes occurring at weathered wood surfaces were examined. Check numbers and dimensions were greater in samples exposed to the full solar spectrum than in samples exposed under filters that blocked the transmission of UV, visible or infra-red radiation. Samples that were shielded from more energetic wavelengths developed less checking. Checks developed in the rays and propagated at the interface between adjacent tracheids, close to the middle lamella. We conclude that exposure to UV and visible light increases the tendency of wood to check during exterior exposure. Our findings suggest that water-repellent treatments designed to prevent wood exposed outdoors from checking should contain additives that restrict the surface photodegradation of wood.
P Evans, K Urban


Spruce and pine heartwood treatment by means of microwave radiation
2008 - IRG/WP 08-40411
An easier penetrability and a more even uptake of wood protection agents is aimed for the two most common wood species in Europe, namely Norway spruce (Picea abies) and Scots pine heartwood (Pinus sylvestris), particularly when there is a great difference in absorption behavior of sapwood and heartwood. Microwave conditioning can improve permeability, reduce density and heat conductivity and change dimensional stability of wood. It could also improve the permeability of refractory wood species. This study deals with the evaluation of different parameters of a microwave treatment and their influence on the penetrability of water during dipping and impregnation of Scots pine heartwood and Norway spruce. Microwave irradiation lead to an increased water uptake after a submersion test, and after vacuum and pressure impregnation of the tested samples. This effect was more pronounced for Scots pine heartwood samples than for spruce wood samples. A short process with high microwave energy is recommended in order to reduce the development of large cracks but to increase the sorption behavior due to small checks in wood.
A Treu, H Rieche, H Militz


Spruce and pine heartwood treatment by means of microwave radiation
2008 - IRG/WP 08-40411
An easier penetrability and a more even uptake of wood protection agents is aimed for the two most common wood species in Europe, namely Norway spruce (Picea abies) and Scots pine heartwood (Pinus sylvestris), particularly when there is a great difference in absorption behavior of sapwood and heartwood. Microwave conditioning can improve permeability, reduce density and heat conductivity and change dimensional stability of wood. It could also improve the permeability of refractory wood species. This study deals with the evaluation of different parameters of a microwave treatment and their influence on the penetrability of water during dipping and impregnation of Scots pine heartwood and Norway spruce. Microwave irradiation lead to an increased water uptake after a submersion test, and after vacuum and pressure impregnation of the tested samples. This effect was more pronounced for Scots pine heartwood samples than for spruce wood samples. A short process with high microwave energy is recommended in order to reduce the development of large cracks but to increase the sorption behavior due to small checks in wood.
A Treu, H Rieche, H Militz


The Effects of Solar Radiation on the Fungal Colonization and Color of Weathered Wood
2008 - IRG/WP 08-10676
Solar radiation rapidly depolymerizes lignin at wood surfaces exposed outdoors producing a suite of low molecular weight aromatic compounds within weathered wood. Fungi colonizing weathered wood are able to metabolize these aromatic compounds, and many of them also contain high levels of melanin to protect themselves from the harmful effects of UV radiation. Both of these adaptations suggest that solar radiation directly and indirectly influences the colonization of weathered wood by fungi. In this study we test the hypothesis that exposure to solar radiation affects the colonization of wood by fungi and the resulting color of the weathered wood. Lodgepole pine decking samples were exposed outdoors for 40 weeks under filters which blocked selected regions of the solar spectrum while allowing other weathering factors to act on samples. Fungi growing at the surface of wood exposed under the different filters were isolated at the end of the exposure period and identified using molecular techniques. The color of the isolated fungi and the weathered wood were also assessed. Wood exposed under filters that transmitted ultraviolet and/or visible light was more frequently colonized by dark colored fungi such as Aureobasidium pullulans and Hormonema dematioides than samples exposed under filters that blocked these components of the solar spectrum. A. pullulans and H. dematioides were also isolated from wood exposed under filters that blocked UV radiation and visible light, but a greater proportion of lighter fungi such as Epicoccum nigrum and Phoma sp. were found in the weathered wood. The color of weathered wood at the end of the exposure trial partly reflected the pattern of fungal colonization. Wood exposed under filters that blocked UV radiation and visible light was greener and lighter than wood exposed under filters that transmitted these wavelengths. We conclude that solar radiation influences the colonization of wood surfaces by fungi and our findings point to a link between the color of the weathered wood and the fungi that colonize the wood.
V Hernandez, C Breuil, P D Evans


Effects of UV Radiation on Melanization and Growth of Fungi Isolated from Weathered Wood Surfaces
2015 - IRG/WP 15-10842
This research tests the hypothesis that fungi isolated from weathered wood will respond to elevated levels of UV radiation by increasing their melanin production. To test this hypothesis, we measured the melanin production and mycelial color of Aureobasidium pullulans and Cladosporium cladosporioides, before and after the fungi were grown under artificial UV, visible light and complete darkness. Two albino fungi: A. pullulans and Ophiostoma piliferum, and one pigmented O. piliferum fungus were used as controls. Our results show that A. pullulans has the ability to increase its production of melanin when exposed to UV radiation. This adaptive response may protect A. pullulans from the high levels of UV radiation found at wood surfaces exposed outdoors. C. cladosporioides was highly melanized, irrespective of exposure to different light sources. Our findings suggest that the discoloration of weathered wood surfaces may be influenced by the response of fungi colonizing wood surfaces to UV radiation. Further research is needed to test this hypothesis.
V A Hernández, P D Evans


Weather degradation of thin wood samples
2016 - IRG/WP 16-20578
Untreated wooden surfaces degrade when exposed to varying doses of natural weathering. In this study, thin wood samples were studied for weathering effects with the aim of modeling the degradation utilizing Near-infrared hyperspectral imaging. Several sets of samples were exposed outdoors for time intervals from 0 to 21 days, and one set of samples was exposed to UV-radiation in a laboratory chamber. Spectra of earlywood and latewood were extracted from the hyperspectral image cubes and changes in the spectra were modeled as a function of UV solar radiation to see if the weathering deterioration was reflected in the NIR spectra. The model was obtained using Tikhonov regression, an algorithm that yields robust prediction models when predicting new test data. Lignin and holocellulose content were estimated on selected samples separately for early- and latewood using a thermogravimetric analysis (TGA). The thermogravimetric curves showed a clear trend with the progress of weathering of the samples, for both earlywood and latewood and both for the outdoor and the UV chamber exposed samples. This indicates that NIR spectroscopy can also be used to model lignin content in the wood. Further studies are planned to confirm this. The result from this work is a first step towards a weather dose model determined by temperature and moisture content on the wooden surface in addition to the solar UV radiation.
I Burud, K A Smeland, K Hovde Liland, T K Thiis, J Sandak, A Sandak, L Ross Gobakken