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Preservative treatment of Pinus elliottii
1987 - IRG/WP 3435
The treatment of Pinus elliottii with copper-chrome-arsenic preservative by four alternative seasoning and treatment methods is investigated. Steam conditioning followed by either alternating pressure method (APM) or 'Q' treatment resulted in inadequate preservative penetration. Air drying or high temperature drying followed by the Bethell process resulted in a high standard of treatment.
P Vinden, L Carter


Resin bleed after light organic solvent preservative treatment - the effect of drying method and process type
1986 - IRG/WP 3378
The effects of drying method and treatment process type on resin bleed were investigated. High-temperature drying of resinous radiata pine (Pinus radiata D. Don) heartwood resulted in improved wood permeability, higher preservative uptake, and greater resin bleed when treated by the Rueping process. Resin bleed was reduced substantially when timber was treated by the Lowry process, and totally eliminated when Bethell-treated. The incorporation of 2% wax into the preservative formulation may control resin bleed after Rueping treatment.
P Vinden


Observations on the uptake and penetration of various liquids in clear heartwood and sapwood of Pinus radiata D.Don
1983 - IRG/WP 3224
Volumetric uptake of water (aqueous copper-chrome-arsenic (CCA)) or methanol, applied by bulk hydrostatic pressure to air dried clear heartwood specimens of Pinus radiata D. Don, far exceeds that of a wide variety of polar and non-polar solvents. In air dried sapwood, the volumetric uptake of CCA tends to be less than that achieved for most solvents including methanol. No comprehensive explanation of the penetration mechanism in these two substrates can yet be offered. High temperature drying effects a significant increase of volumetric uptake of all liquids by heartwood, but not by sapwood, possibly because air dried material is nearly saturated after pressure treatment.
J E Barnacle


Quality of timber impregnated with preservatives of class AB after three years in service
2002 - IRG/WP 02-20241
Quality of impregnated timber is most often expressed by penetration and retention of the preservative used. Relatively less information is available about the performance of the final product, e.g. decks, panels etc. regarding product’s surface checks, deformations and overall appearance. Together with the timber durability, the above mention features are of esthetical importance in the above ground performance of timber. A comprehensive Nordic project dealing with pre-treatment, impregnation, durability and performance of Scots pine timber impregnated with copper-based preservatives for above ground use (class AB) was recently finished. The results from an above ground trail concerning the quality of timber are presented. The timber was dried in a conventional progressive, batch and high temperature kiln prior to impregnation. A significantly better quality regarding checks, deformations and deviation of the final moisture content, was achieved after conventional batch and high temperature dryings. Three preservatives (Kemwood ACQ 1900, Tanalith E and Wolmanit CX-8) were impregnated. The high temperature drying ensured the best penetration of all preservatives, but the retention was lower compared to conventional progressive and batch kiln dried timber. A part of the planks were conventionally kiln dried after the impregnation, the second part was air dried. Two decks with planks covering the variations in primary drying and preservative used were exposed; the former deck was in the open, the later one was under a shelter. After three years in service the planks were assessed regarding checks, deformations and moisture content. All three preservatives showed satisfactory appearance and no indication of decay was found. The deformations were comparable to those measured directly after final drying; the type of exposure had effect on the checks and moisture content of timber.
N Terziev


Effects of drying processes on termite feeding behaviour against Japanese larch wood
2001 - IRG/WP 01-10390
We investigated the effects of current drying schedules for larch lumbers on the termite feedings. Thermal analyses were also conducted to investigate degradation of wood components. Choice feeding tests showed specimens dried under high-temperature schedules were evidently susceptible against termite attacks. These schedules produced the feeding-attractants, which were suggested by the TGA results compared to the control samples. The results of this study indicated that the acceleration of termite feeding is taken place even under comparatively lower temperature than that of our previous researches.
S Doi, Y Kurimoto, H Takiuchi, M Aoyama


Wood kiln drying. Simple process of material treament or soft method of preservation? (Le séchage arificiel du bois. Simple opération de traitement du metériau ou méthode douce de préservation?)
1993 - IRG/WP 93-50001-14
Among the processes enabling to extend wood durability, kiln drying can be considered as a treatment and soft preservation method. Dry woods are naturally durable provided they are not subject to important retaking of the moisture. Drying thanks to the application of temperatures from 50 to120°C enable to execute a thermic treatment which kills grubs and mushrooms to ensure a sterilization that can be durable if wood doesn't retake water. Noumerous connections and analogies between drying process and the preservation one enable to conclude that kiln drying is a real operation of wood treatment either curative or to a smaller extent preventive.
F More-Chevalier


Termite durability of sugi (Cryptomeria japonica) heartwood kiln-dried under high-temperature process in relation to wood extractives
2005 - IRG/WP 05-10547
Termite durability of sugi heartwood samples kiln-dried under a high-temperature process were evaluated by using Reticulitermes speratus (Kolbe) as a test termite sp. The n-hexane extractives of these samples were analysed by a GC technique. The less termite durability was shown on the wood samples dried under the high-temperature process, in comparison with that of the air-dried samples. No GC-peak assigning to cubebol and epicubebol was shown in n-hexane extractives of kiln-dried samples.
S Shibutani, E Obataya, K Hanata, S Doi


Gaseous preservative treatment of wood
1990 - IRG/WP 3631
A recent development in processing wood with a gaseous preservative means that dry, treated wood can be produced in under 30 hours with the benefits of product diversification, faster stock turnover and the ability to respond to short term demand. About 400,000 m³ of wood are treated each year in New Zealand with boron salts to protect from borer infestation. Traditionally this treatment is effected by dipping the freshly sawn wood into a solution of boron salts and then stacking the wood while the salts diffuse through it. For 50 mm thick timber the diffusion process takes from 5 to 8 weeks. The Forest Research Institute has developed a new technique whereby the treatment is carried out in the gas phase effecting full impregnation within seconds. This process is carried out in a pressure vessel, which acts as both a kiln, preservation vessel and steam conditioning chamber. The wood is first high temperature dried to a low moisture content, exposed to a vapourised organoborate and then steamed. Total time in the vessel is about 30 hours. Preservative treatment in the gas phase is a novel development for the wood processing industry. An outline of the development of the process is presented and the implications for this industry are discussed.
R Burton, A J Bergervoet, K Nasheri, P Vinden, D R Page


Low temperature drying conditions of Pinus radiata wood for avoiding internal stain
1989 - IRG/WP 3507
It has been observed that, if in little sawmills, timber is dried with a low temperature schedule, it arrives at destination with internal sapstain besides of superficial mould. In this study, the lowest drying temperature at which wood should be exposed for sterilization, which results to be 52°C, is searched. It is not possible to avoid entrainment of pentachlorophenol, even though a waiting period of 72 hours after dipping the wood in a pentachlorophenate/borax solution before drying is considered. The residual content of pentachlorophenol in wood should be at least 400 µg/cm² or the moisture content less than 23% for avoiding the development of mould.
M C Rose


Comparative investigations on the influence of wood seasoning, wood properties and temperature on the toxic values of wood preservatives against Hylotrupes egg larvae
1970 - IRG/WP 28
Comparative tests carried out at three institutes indicated the influence of kiln temperature, position of wood specimens in the cross sectional area and test temperature on the toxic values determined in accordance with DIN 52165 with egg larvae of the house longhorn beetle (Hylotrupes bajulus L.). The preservatives applied were boric acid in distilled water and g-benzene-hexachloride dissolved in chloroform; the timber species used was pine sapwood, (Pinus sylvestris L.). The method of seasoning had no influence on the toxic values of boric acid. With the g-BHC, however, the toxic values gradually increased with rising kiln temperatures (20°C, 70°C, 105°C). With boric acid the position of the sapwood samples in the log had no influence on the toxic efficacy; with g-BHC the efficacy was slightly greater in the outer sapwood, compared with the inner sapwood. The test temperatures (20°C, 24°C, 28°C) yielded different toxicity results for boric acid. At 24°C and 28°C the threshold values were somewhat below those of 20°C; they agreed with the values obtained at 20°C after a longer test period. With g-BHC different temperatures did not affect the results. An explanation is suggested for the causes of the influence exerted by the kiln temperature and wood properties on the toxic values of g-BHC. There was good agreement between the toxic values obtained in the different institutes.
G Becker, T Hof, O Wälchli


Changed susceptibility of the chemically and thermally degraded spruce wood to its attack by the dry rot fungus Serpula lacrymans
1999 - IRG/WP 99-10322
In buildings, some intentional or unintended situations can occur at which some wood products are exposed to aggressive chemicals and also to higher temperatures. Occasional activity of fungi on such pre-attacked wood products can be either higher or lower. This paper deals with changes in the susceptibility of spruce wood (Picea abies L. Karst.) to attack by the dry rot fungus Serpula lacrymans, in such situations, when the wood samples 8.5x8.5x120 mm3 (RxTxL) were first pre-treated with 1% water solutions of selected acids (H2SO4, CH3COOH), bases (NaOH, NH4OH) or oxidizing agent (H2O2), or they were also exposed to a higher temperature (190°C/3h). The activity of S. lacrymans was totally restricted only in one situation, if the wood was pre-treated with sulphuric acid and then exposed to 190°C. On the other hand, specimens pre-treated with ammonium hydroxide were more susceptible to bio-attack (in both situations: without or with high temperature pre-treatment effect) than sound ones.
L Reinprecht


Fixation of CCA in Pinus sylvestris after kiln-drying
1990 - IRG/WP 3594
Tanalith C Paste is 98% fixed and Tanalith Oxide C is 99% fixed irrespective of whether treated Pinus sylvestris is kiln or air dried. A schedule suitable for kiln drying of CCA treated Pinus sylvestris is described.
P Warburton, J A Cornfield, D A Lewis, D G Anderson


The effect of high temperature and long pressing time on the dimensional stability and decay resistance of OSB
2002 - IRG/WP 02-40237
The exterior use of OSB is restricted because when it is exposed to wet conditions swelling, loss of internal bond strength (IB) and decay occur. In this study an alternative process of pressing which results in the production of dimensionally stable and a more decay resistant strandboard was investigated. Boards were pressed at elevated temperatures for prolonged pressing cycles and their physical (thickness swelling and water absorption after 2 and 24 hours soak), mechanical properties (IB, MOR, MOE) and decay resistance were assessed. Analysis of variance (ANOVA, p=0.005) between pressing time/temperature and each property tested were used for the assessment of the results. The decay resistance of the boards was tested according to a draft European standard (DD ENV 12038: 1996) with a slight modification to the sample size. Boards were tested against Coniophora puteana, Postia placenta, Trametes versicolor and Pleurotus ostreatus. The results of this study showed that the increase of pressing time and temperature resulted in significant reductions in the thickness swelling and water absorption of the boards. The treatment had little effect on board mechanical properties. The resistance to fungal biodegradation was significantly improved at the higher temperature / pressing time combinations tested. The results of this study show that the production of a dimensionally stable and a more decay resistant OSB is possible without excessive use of preservative chemicals. If adopted these findings may lead to the development of new wood-based panel products (non-preserved dimensional stable and decay resistant hazard class 3-OSB) which may replace preservative treated plywood and solid wood for many exterior construction applications.
G J Goroyias, M D C Hale


Experiences from a Danish large scale test by means of a new method of treatment by attack of true dry rot fungus (Serpula lacrymans) in buildings
1994 - IRG/WP 94-10064
Experiences from a new and epoch-making method of treatment in connection with the repair of attack of the true dry rot fungus, Serpula lacrymans (Fr.) S.F. Gray, are described. The paper presents the background of a large scale test comprising repair of more than 150 Danish buildings over a period of approximate 5 years. The method being both gentle to the building and presenting savings of at least 70% compared with the traditionally known repairing methods is based on thorough recording of the extent of attack and examination of the vitality of the fungal attack combined with a changed chemical and constructive treatment including treatment by means of a newly developed heat treatment based on high frequency radio waves. Continuous controls have confirmed the applicability in practice of the method. Beyond the method, the paper discusses the consequences as regards security, possibilities of insurance and obtaining a mortgage loan.
O Munck, H Sundberg


Heat transfer and wood moisture effects in moderate temperature fixation of CCA treated wood
1994 - IRG/WP 94-40022
Practical aspects of heat transfer and fixation of wood exposed to drying conditions after CCA treatment are considered. The rates of heat transfer and CCA fixation are substantially influenced by the cooling effect of water evaporating from the wood surface when drying occurs during fixation. At least in the early stages of fixation, the wood temperature approaches the wet bulb temperature, rather than the dry bulb temperature of the fixation chamber. Some drying during fixation is acceptable, but the time to complete fixation will be extended significantly, depending on the dry bulb/wet bulb depression. At above ambient temperatures, complete hexavalent chromium reduction can occur relatively quickly in relatively dry wood. However, CCA deposited under these conditions is more easily leached from wood and fixation conditions must be controlled to prevent wood from reaching fibre saturation point moisture content before fixation is complete.
J Chen, M Kaldas, Y T Ung, P A Cooper


Clean creosote - its development, and comparison with conventional high temperature creosote
1983 - IRG/WP 3235
Pigment emulsified creosote (PEC) is presently being tested and shows considerable stability in terms of water content, pigment level, pH, viscosity, rheological behaviour and microscopy. Timber samples from several eucalypt species have been treated with PEC and side matched samples treated with conventional high temperature creosote (HTC). The PEC treated specimens showed higher weight retentions of total preservative, (based on sapwood volume) than did the HTC treated samples. In terms of whole creosote however, retentions were not significantly different. Fuming was negligible immediately the PEC treated samples were removed from the pressure cylinder. In addition, the surface of freshly treated PEC samples was drier and much easier to handle than HTC treated samples and they remained dry even after eight months of weathering. 'Crud' formation on the surfaces of the exposed PEC samples was less than the corresponding HTC samples. There was no apparent difference in the penetration and macro-distribution of the two preservatives in the sapwood of matched samples. Full depth of sapwood penetration of both preservatives was visible.
C W Chin, J B Watkins, H Greaves


Investigation of extracellular mucilaginous material in some wood decay fungi
1996 - IRG/WP 96-10188
The external morphology of the extracellular mucilagenous material (ECM) produced by Coriolus versicolor and Coniophora puteana during colonization of Scots pine and beech was studies using SEM. Specimens were examined in the frozen hydrated, freeze-dried and critical point dried state. All technics produced artefacts but the ECM was best preserved when examined the frozen hydated state. Critical point drying damaged the ECM extensively but was useful in partly explaining its nature. ECM was found to line much of the lumen and coated aerial fungal mycelium. Some morphological patterns in which the ECM and fungal hyphae were involved are also descibed.
A R Abu, D J Dickinson, R J Murphy


Sterilization to limit pretreatment decay: Internal temperature during kiln drying of Douglas-fir poles
2001 - IRG/WP 01-40206
Sterilization to limit pretreatment decay: Internal temperature during kiln drying of Douglas-fir poles. Fungal colonization of poles following peeling has been the subject of considerable concern among electric utilities. While the presence of fungi does not, in itself constitute a risk, the survival of these fungi through the conventional treating processes could allow them to continue to degrade the pole once it is placed in service. Previous research has shown that pressure treatments in heated, oil-based solutions expose the poles to sufficient heat to eliminate established decay fungi. Many treaters in North America are shifting towards kiln drying to reduce treatment times, but there is little data on the internal temperatures in poles during conventional kiln treatments. In this report, we describe field tests to monitor internal temperatures in Douglas-fir poles during treatment. In general, temperatures did not reach the generally accepted lethal target temperature for eliminating fungi from wood (67°C for 75 minutes), but the times when temperatures were between 60 and 65°C approached 40 hours in some charges. Prolonged exposure to these elevated temperatures should also eliminate established decay fungi. The results suggest that internal temperatures during kiln drying reach levels that should eliminate the risk of pre-treatment decay fungi surviving the treatment process.
J J Morrell, P G Forsyth, K L Levien


Comparison of the in-ground performance of pigment emulsified creosote (PEC) and high temperature creosote (HTC)
2000 - IRG/WP 00-30217
A long-term field trial was conducted in Australia to compare the in-ground performance of two oil-borne preservative formulations, conventional high temperature creosote (HTC) and a modified creosote formulation, pigment emulsified creosote (PEC). Three retentions (50, 100 and 200 kg/m³) were targeted for each formulation. An additional retention of PEC formulation (308 kg/m³), which contained 200 kg/m³ of creosote, was also included in the trial. Treated and untreated Eucalyptus regnans sapwood specimens were exposed horizontally below-ground to a range of economically important species of subterranean termites and wood decay fungi at two tropical and one semi-arid test sites. After 11 years of exposure, specimens treated with 200 kg/m3 of HTC and specimens treated with PEC containing 200 kg/m3 of creosote continue to perform well. Results of the field trial demonstrate that PEC will perform comparably to HTC on an equivalent creosote retention basis.
J W Creffield, H Greaves, N Chew, N K Nguyen


The loss of insecticidal action from synthetic pyrethroid-treated wood samples: The effect of high temperatures and relative humidities
1992 - IRG/WP 92-1569
This paper describes the results from bioassays using Hylotrupes bajulus, and chemical analyses, of pyrethroid-treated wood samples following storage for up to 3 years. A range of four storage environments was used consisting of combinations of two temperatures (20°C and 40°C) and two relative humidities (60% and 90%). It is concluded from the chemical analyses that, although losses at room temperature were small, at the higher temperature used in this study loss of insecticide was accelerated. Exposure of treated wood to high relative humidity did not appear to result in increased loss of insecticide. The bioassay results confirmed these conclusions. The significance of the bioassay results in relation to the long term efficay in service of preventive treatments is discussed and a logic proposed for deriving a service life on the basis of which an estimate of up to 58 years protection from current commercial formulations is derived.
R W Berry, S J Read


Durability of Sugi (Cryptomeria japonica D.DoN ) wood treated in high temperature liquid paraffin
2002 - IRG/WP 02-40221
Sugi(Cryptomeria japonica D.DoN )wood was subject to a heat treatment in high-temperature liquid paraffin for the purpose of improving the resistance against fungi and termites without chemicals. The bath of paraffin liquid, which can provide a uniform heat transfer (±2?), was used at temperatures of 90?,120?and 150?.?ecay resistance according to JIS K 15711) was evaluated using a brown rot fungus(Fomitopsis palustris). Termite resistance according to JWPA standard 112) was conducted using a termite(Coptotermes formosanus Shiraki). Paraffin-treated wood had decay and termite resistance, however its effectiveness disappeared when the paraffin of wood surfaces was removed. The difference of durability didn’t depend on the treatment conditions of the temperature and time.
Y Matsuoka, W Ohmura, S Fujiwara, Y Kanagawa


Partial seasoning and preservative treatment systems for pine roundwood
1982 - IRG/WP 3187
Experimental trials at FRI, Rotorua showed that the steaming schedule normally used for steaming and venting is also suitable for steaming and vacuum seasoning. Applying vacuum of up to -84 kPa immediately after steaming did not increase the initial loss of wood moisture significantly in comparison to steam/venting. The main improvement to wood condition by using steam/vacuum appeared to be to distribution of moisture within, and possibly between, posts. Bethell treatment of Corsican pine posts one day after steam/vacuum was not of a satisfactory standard. However, the steam/vacuum/Bethell system may offer a worthwhile reduction in the holding period specified for the steam/vent/Bethell ('Q') system. A shortened and simplified Alternating Pressure Method (APM) process was used to treat Corsican pine posts one day after steam/vacuum. The standard of treatment obtained by using this system was evaluated at FRI and at a commercial treatment plant and showed potential to treat wood to low retention variability. As a result of these trials the New Zealand Timber Preservation Authority has approved a steam/vacuum/APM schedule for the treatment of radiata and Corsican pine rounds up to 250 mm large end diameter.
A J Bergervoet


High Temperature Treated Wood
2008 - IRG/WP 08-40429
High temperature can modify internal structure and physic-chemical properties of wood by a controlled pyrolysis process. Such treatment, among other changes in properties, modifies the wood color in a way that resembles exotic species, increasing its market value. The main objective of this work is to determine the changes in wood properties caused by the effect of temperature and time, in order to establish patterns of time for treatments performed at 220 °C through correlations based in heat transfer concepts. The high temperature treatment will be set at 220 °C during 20, 30 e 40 minutes in body tests of Pinus spp, using an electric wood dryer without steam, while the volume and mass of the wet wood, the dry wood (0%) and after the treatment ends will be controlled and measured. The results of alterations in color, hardness and dimensional stability of the wood and the data (with different temperature treatments) will be useful to set standards for high temperature treatments using theoretical concepts of heat transfer applied to the wood material, considering the wood properties variation, including cost effectiveness of wood products.
C C Borges, A L Barbosa, R Faber de Campos, S T Targas


Proposal for further work on accelerated ageing
1988 - IRG/WP 2314
M-L Edlund


Solvent drying and preservation of timber
1977 - IRG/WP 381
Processes which combine drying and preservation are first reviewed. Some preliminary experiments are then described in which blocks of green Sitka spruce sapwood were immersed, in a solution of tributyltin oxide (TBTO) in methanol at 60°C. Satisfactory penetration of the preservative and exchange of methanol and water occurred in a few hours. The methanol was removed rapidly from the wood by evaporation. Satisfactory penetration of TBTO into initially methanol-saturated samples occurred in a similar period. The factors influencing. such treatments are discussed. High initial moisture content of the wood and a high operating temperature are particularly desirable. Some aspects of the possible commercial operation of the process are discussed.
J A Petty


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