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Inhibition of wood decay and termite damage by calcium precipitation
1996 - IRG/WP 96-30111
Fungal decay of wood in service, especially brown rot, results in billions of dollars (US) of losses annually. Recent environmental restrictions, both U.S. and international, are limiting or eliminating the use of broad spectrum biocides for wood preservation, primarily due to problems with disposal. In order to design new, environmentally benign methods for control of wood decay fungi, it is essential to understand the precise sequence of biochemical events as wood is colonized. The production of polygalacturonase (PG) and hydrolysis of bordered pit membranes during incipient brown-rot decay has recently been described by our laboratory. One key to pectin hydrolysis by plant pathogens has been shown to be fungal production of oxalic acid which lowers the pH of the substrate and chelates calcium ions. Production of oxalic acid may serve a similar role during incipient wood decay as calcium oxalate has been visualized by scanning electron microscopy during both brown-rot and white-rot decay. Therefore, it was hypothesized that in situ precipitation of existing calcium ions in wood may prevent the cascade of biochemical events involved in colonization of wood by brown-rot fungi, expecially hydrolysis of bordered pit membranes. Preliminary experiments in our laboratory have shown that brown-rot fungi, white-rot fungi, and termites are inhibited from effecting weight loss of wood following pretreatment of wood blocks with the selective water soluble calcium precipitating agent N,N-naphthaloylhydroxylamine (NHA).
F Green III, T A Kuster, L Ferge, T L Highley


Inhibition of termite damage by N'N-napthaloylhydroxyamine (NHA): Reticulotermes flavipes (Kollar) vs. Coptotermes formosanus Shiraki
2000 - IRG/WP 00-10354
The calcium precipitating agent NHA has been shown to protect southern yellow pine (SYP) from wood decay and termite damage comparable to CCA in field tests (Gulfport, MS) for two years (Crawford and Green, 1999). In a collaborative study, SYP wood blocks were vacuum treated with three concentrations of aqueous NHA and exposed in a no-choice test to Eastern subterranean termites (FPL, USA) and Formosan subterranean termites (WRI, Japan) to determine protection against termite damage. Individual blocks (leached and unleached) were exposed to R. flavipes (AWPA) or C. formosanus (JWPA) for 3-4 weeks. Mean weight loss of wood blocks after termite exposure ranged from 0.0 to 18.0% for R. flavipes and 6.0 to 20% for C. formosanus. Wood blocks exposed to R. flavipes were completely protected by 0.5 and 1.0% NHA, but weight loss in similar blocks challenged by C. formosanus were 6.0% and 6.2% respectively at the same concentrations. NHA acted as an effective termiticide for R. flavipes with 100% mortality after 3 weeks, but only soldiers were preferentially killed in C. formosanus. Formosan subterranean termite workers showed enhanced resistance to NHA treatment when compared to Eastern subterranean termites.
F Green III, S T Lebow, T Yoshimura


Mineralization of European oak with various ionic salt solutions to achieve an in situ precipitation of calcium oxalate
2019 - IRG/WP 19-40861
Thin specimens of European oak (Quercus spp.) with the dimensions of 4 × 20 × 50 mm3 were treated with various aqueous ionic salt solutions of calcium chloride, potassium oxalate and calcium acetate. Additionally, the oak was treated with combinations of calcium chloride and potassium oxalate, as well as calcium acetate and potassium oxalate with the aim to precipitate in situ the water insoluble salt calcium oxalate. The specimens were impregnated in an autoclave under pressure with the single compounds, as well in combinations in a two-step process, successively. The treatability of the oak was determined by means of the bulking coefficient and due to segment electron microscopy investigations. Possible precipitation to calcium oxalate in situ in oak was determined by ATR-FTIR measurements and a changing moisture uptake after the two-step impregnation serves as a further indicator for a calcium oxalate precipitation. The study shows, that thin oak lamellas can be impregnated with the investigated solutions and additionally, the data obtained in this study indicating that there is an in situ precipitation to the wanted water insoluble salt calcium oxalate and the corresponding by-product.
T Franke, T S Volkmer


Wood in concrete. Summary of discussion at IRG 14, Surfers Paradise, Australia
1984 - IRG/WP 3264
The performance of untreated and preservative treated wood when placed in direct contact with concrete was considered in a discussion session at IRG 14. While published reports in this area are scarce, research is in progress internationally and a variety of practices are currently available to minimize any additional hazard posed by contact with concrete. This report summarizes the points raised at the IRG discussion.
R J Murphy


Collaborative soft rot tests: Results of analyses of soil samples
1976 - IRG/WP 263
C R Levy


Leachability of borate-modified oriented strandboard: A comparison of zinc and calcium borate
2002 - IRG/WP 02-40232
The leachability of boron in zinc and calcium borate-modified oriented strandboard (OSB) was investigated in this study. The leaching experiments were conducted by exposing edge-sealed OSB samples under running water for 8, 24, 72, and 216 hours. The results were compared with those from the unleached controls. Boron leaching of the modified OSB occurred upon the initial water exposure, and the leaching rate decreased as the leaching time increased. Borate type, initial BAE level, wood species, and sample thickness swelling significantly influenced the leachability. There was no consistent effect of polyethylene glycol (PEG) on zinc borate leaching. Calcium borate with a smaller particle size helped reduce its leachability. The glueline washing due to thickness swelling of the test samples under water and decomposition of the borate to form less water-soluble boric acid are thought to be two possible causes for the observed leaching. The relationship between assayed BAE and leaching time followed a decaying exponential function for zinc borate OSB and a Harris decaying power function for calcium borate OSB. The material constants of the regression models allow comparing leachability of the modified OSB for various wood species. A unified leaching method for treated wood composite materials is needed.
S Lee, Q Wu


CCA Chemistry
1983 - IRG/WP 3268
A Pizzi


The course of fixation of Cu-Cr-As wood preservatives
1972 - IRG/WP 307
Copper-chrome-arsenic (CCA) preservatives in contact with wood result in an instant extensive increase of pH, because of ion-exchange and adsorption reactions with the wood. During precipitation of the active elements the pH continuously increases but reaches a maximum, when all chrome is consumed. Some of the early reaction products are unstable and slowly convert via dissolution into stable compounds. The conversion proceeds by proton liberating as well as proton consuming reactions. The pH therefore alternatively decreases and increases until the reactions cease after several months. The final equilibrium fixation products are: ion-exchange fixation of Cu to the wood CrAsO4, Cu(OH)CuAsO4 and Cr(OH)3. The chrome fixation is 2nd order with respect to hexavalent chrome in the liquid phase, four regions with distinct chrome fixation rate constants were found. A hypothesis is given for the mechanism of fixation.
S-E Dahlgren


Oxalate production and calcium oxalate accumulation by Gloeophyllum trabeum in buffered cultures
1994 - IRG/WP 94-10075
Most basidiomycetous fungi produce oxalic acid as a result of their metabolic activities and nutrient procurement. There is currently a renewed interest in the role that oxalic acid may play in the decomposition of wood by basidiomycete fungi. It has been observed that although most wood degrading fungi have the capacity to produce oxalic acid, not all of these organisms express this capacity equally in the wood environment. In addition, not all of the fungi which produce oxalic acid will accumulate this metabolite. Very often the production of oxalic acid is coincident with the precipitation of oxalate salts such as calcium oxalate. At this time it is unclear as to what controls the differential production and accumulation of oxalate by wood degrading fungi. An investigative series of experiments was established using the brown rot fungus Gloeophyllum trabeum to examine the conditions which favor oxalate production and accumulation as manifested through the production of metastable calcium oxalate dihydrate crystals. Batch cultures which were buffered by base cation exchange sites of mineral amendments stimulated the production of calcium oxalate crystals. The results of these buffering experiments indicate that at pH values below approximately 6.0 there is a diminution of oxalate accumulation, and that a pH environment of approximately 3.0 is consistently attained in weakly buffered cultures inoculated with this fungus. These pH values correspond to the pH optima for oxaloacetase (EC 3.7.1.1) and oxalate decarboxylase (EC 4.1.1.2) respectively, and thereby suggest a mechanism for both pH control and oxalate production and accumulation.
J H Connolly, J Jellison


A comparison of inductively coupled plasma spectroscopy and neutron activity analysis for the determination of concentrations in wood
1993 - IRG/WP 93-10048
As wood decays the ionic composition changes, with increases often being seen in the concentrations of Ca, Mg, Fe, Mn and sometimes K. The concentration of eight cations in red spruce sapwood and heartwood samples was determined independently by inductively coupled plasma spectroscopy (ICP) and by neutron activation analysis (NAA) as part of an effort to standardize our analytical procedures and create a uniform wood standard for use by multiple researchers. Preliminary studies indicate a difference in the values of Ca and K as estimated by ICP and NAA, possibly due to a loss of these elements due to volatilization during ashing.
J Jellison, J Connolly, K C Smith, W T Shortle


Decay and mold resistance of borate modified oriented strandboard
2003 - IRG/WP 03-40260
Decay and mold resistance of zinc borate (ZB) and calcium borate (CB) modified oriented strandboard (OSB) from southern mixed hardwoods and yellow pine was investigated in this study. Tests were done with brown rot, Gloeophyllum trabeum, and white-rot, Trametes versicolar, fungi for 8 and 12 weeks, respectively. Wood species and fungus type had significant influence on the decay resistance. Decay caused by brown rot was evident for all untreated southern pine and mixed hardwood OSB controls. White rot, however, did not cause significant sample weight loss for both species groups. The incorporation of ZB and CB into the OSB provides suitable protection against brown- and white-rot fungi. No significant weight loss was observed from the treated OSB. Microscopic analysis shows that the hyphae were abundant in wood rays and cell walls in the southern pine OSB controls attacked by G. trabeum. Untreated samples from mixed hardwoods and commercial OSB were most susceptible to mold growth. The borate-modified OSB from mixed hardwoods and southern pine effectively prevented the mold growth. Mold resistance was achieved with increase of borate retention level in the samples. Mixed hardwoods OSB showed a higher susceptibility to mold growth than southern pine OSB with or without borate treatment.
Q Wu, S Lee, J P Jones


A comparison of the leaching resistance of diammine-copper complexes and copper carbonate precipitated in wood
1997 - IRG/WP 97-30158
Previous studies have shown that during treatment of wood with ammoniacal copper solutions, both simple copper precipitates and diammine-copper complexes are formed. The objective of the present study is to determine the relative importance of both forms of copper, on such aspects as preservative leachability and biological performance. In the current experiment, the leachability of copper carbonate precipitated in wood is compared with that of diammine-copper complexes. The results confirmed that both forms of copper resisted leaching by distilled water. However, when exposed to the more aggressive leaching conditions using the sodium citrate buffered solution, the diammine-copper complexes were significantly more ressistant to removal from the wood. Further studies are planned to examine the diammine-copper complexes present in the wood as well as the efficacy of these complexes against wood decay fungi.
Xiao Jiang, J N R Ruddick


Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 6: The length of the primary precipitation period
1975 - IRG/WP 359
The end of the primary precipitation fixation period of CCA preservatives coincides with the first peak in pH versus time. This offers a simple way of estimating the duration of the period. The duration is determined by a number of factors and their interactions, the most important of which are: wood species (anatomy, natural pH, accessibility of reducing agents), preservative type, preservative concentration and temperature. For interpretation of experimental data the effect of these factors is discussed in the light of the chemistry and the mechanism of fixation of CCA preservatives. For a proper handling of the treated timber, knowledge of the duration in actual working conditions is essential.
S-E Dahlgren


Alkaline building materials and controlled moisture conditions as causes for dry rot Serpula lacrymans growing only in houses
1985 - IRG/WP 1272
Dry rot Serpula lacrymans ( Fr.) S.F. Gray is commonly found in houses, though never with certainly in nature, like other wood destroying fungi which grow both indoors and outdoors. In investigating series of dry rot instances it was shown that this fungus is always found in covered places, close to a moisture source, the distance being from 0 a maximum of 600 cm. Owing to the dry rot has been able to humidfy woodwork to the optimum condition of 20-30% wood humidity, while a lethal water content of 55% would be reached outdoors. At the same time the close presence of alkaline building materials, such as mortar, a clay layer, plaster or concrete has been observed in all instances, the average distance being from 0-100 cm. By neutralizing the dry rot fungus large production of oxalic acid the alkaline materials are able to adjust the pH to optimum levels. These two conditions are the reason why the dry rot fungus only occurs in houses.
J Bech-Andersen


Old and new facts on the dry rot fungus Serpula lacrymans
1991 - IRG/WP 1470
The article collates some of the recent literature on the biology of the dry rot fungus Serpula lacrymans. The fungus can grow at 28°C, and maximum wood moisture is above 55%. Serpula Iacrymans degrades crystalline cellulose. The intensive production of extracellular oxalic acid is neutralized by calcium and iron. There is considerable variation among the strains with regard to factors such as growth rate, wood decay and response to preservatives. Possible alternative methods of eradication involve interference with the metabolism of nitrogen and sugars. Gel electrophoresis of mycelial proteins and immunological procedures provide valuable supplementary means of identification. Fruit-bodies can be obtained regularly in artificial culture. Inter-stock breeding of monokaryons to dikaryons up to the third generation shows differences among cultures with regard to growth, reaction to temperature, rate of wood decay and resistance to chemicals
O Schmidt, U Moreth-Kebernik


Investigations into the biology of Meruliporia incrassata
2004 - IRG/WP 04-10508
The dry rot fungus Meruliporia incrassata (Berk. and Curt.) Murr. is a highly destructive brown rot wood decay fungus and is a significant pest of wooden structures. The fungus, know commonly as ‘Poria’, is characterized in culture by strand mycelium and skin-like surface mycelium. In structural environments it is found to produce prominent water conducting rhizomorphs, is a copious spore producer, and is an aggressive brown rot fungus in wood. This research focuses on the growth of M. incrassata in modified ASTM soil block jars and on the organism's ability to sequester calcium, iron, and other cations from the environment. Four field isolates of M. incrassata, as well as M. incrassata ATCC 11236, and the related dry rot fungus Serpula lacrymans ATCC 36335 were grown on spruce wood in modified ASTM soil block jars for 12 weeks (ASTM 1994). Blocks were dried, weighed, ground and analyzed by ICP (inductively coupled plasma spectroscopy). Weight loss and levels of Ca, K, and Fe were greater in spruce wood decayed by the four field isolates than in wood incubated with the other fungi or with no fungi. The variability in ability to decay wood has implications for standardized decay testing. Understanding the sequestration and role of cations by this highly aggressive dry rot may aid in the development of appropriate control measures.
J Jellison, C Howell, B Goodell, S L Quarles


Production, function and neutralization of oxalic acid produced by the dry rot fungus and other brown rot fungi
1987 - IRG/WP 1330
The formation of oxalic acid by the wood-destroying fungi causing brown rot, is found to be the key which by hydrolysing the hemicellulose brings the cellulose in the tracheid wall in contact with the cellulase enzymes and yeld watersoluble sugars leaving only a lignin skeleton. To control the pH in the substrate the excess oxalic acid is precipitated to water insoluble calcium oxalate by the dry rot fungus in contact with a calcium source. As source glass can be used, however, mortar, concrete or clay soil is better. Heavy metals that form complex compounds with oxalic acid can substitute calcium certain to a degree. The wet rot fungus Coniophora putenea is not dependent on calcium like the dry rot fungus. By producing acetic as well as oxalic acid it might form a buffer solution which controls the pH in the substrate.
J Bech-Andersen


Effect of post-treatment processing on leachability of ACZA-treated douglas-fir lumber
1998 - IRG/WP 98-50109
The effect of post-treatment procedures that more rapidly precipitate copper, zinc, and arsenic in douglas-fir treated with ammoniacal copper zinc arsenate (ACZA) on subsequent leaching resistance were investigated at two retentions (6.4 and 40 kg/m3). Total leaching was greater from boards treated to the higher retention. At both levels, copper was lost at the highest rate. Post-treatment processing had no consistent effect on leaching losses indicating that accelerating precipitation of ACZA does not change its long term sensitivity to loss from the wood when placed in aquatic exposures.
J J Morrell, C S Love, S Kumar, C M Freitag


Serpula lacrymans the dry rot fungus. Revue on previous papers
1989 - IRG/WP 1393
It is found that the Dry rot fungus Serpula lacrymans grows in houses only because of its need for basic materials to neutralize the oxalic acid production or heavy metals which celate the oxalic acid. The average distance from the mycelium to the basic materials is found in average to be 14.2 cm with a variation from 0-100 cm. In contrast to Serpula lacrymans the Coniophora puteana and the Rigidophorus vitreus do not need calcium. The oxalic acid is found to hydrolyze the hemicelluloses and open for further break down of the celluloses. The excess oxalic acid is neutralized by calcium to the water insoluble calciurnoxalate which at last will be broken down by bacteria in the soil. The Dry rot fungus (Serpula lacrymans) (Schum ex Fr.) S.F. Gray, is found in houses and mines only in contrast to other wood destroying fungi which both grow indoors and outdoors in the nature.
J Bech-Andersen


The influence of cement and calcium compounds on the performance of CCA preservatives
1983 - IRG/WP 3221
The influence of cement and calcium compounds on the durability of untreated and CCA treated wood is considered. Calcium compounds were found to reduce the toxicity of a CCA preservative to a soft rot fungus at copper to calcium ratios of 1:1 and 1:10 using a cellulose filter paper technique. Further studies are outlined and some possible mechanisms by which cement and calcium compounds may affect the performance of CCA preservatives are discussed.
R J Murphy


Effects of bleaching process on the roughness values of wood surfaces of Lebanon cedar (Cedrus libani A. Rich.) and Black poplar (Populus nigra L.) using NaOH (sodium hydroxide), H2O2 (hydrogen peroxide) and Ca(OH)2 (calcium hydroxide)
2008 - IRG/WP 08-40403
Technical progress in the wood industry has been rapid in recent times. In this case, the quality assurance of the consumer products aligned with aesthetics value appears as one of the most important parameters. Because of the outer appearance of goods exert an effect on customers, interest in production of high quality surfaces of wooden commodities has increased essentially based on the surface smoothness (and/or the surface roughness of wood) aiming to reach the customer-oriented quality criteria. An aesthetics behaviour is being more influenced than the functional situation of the merchandise when the customers making the decision to buy wood products. It has been well estabilished that some of the properties of wood material (i.e. density, porosity, moisture content, fiber directions), and the wood machining process and its conditions (i.e. kinematics of the cutting process, wood sanding process) make the surface smoothness of wood problematic. There is a lack of information about the effects of bleaching process (i.e. one of the special technical ways to increase the aesthetics of wood products) on the smoothness of wood surfaces despite numerous reports published on the machining tools and the cellular structure of wood. In this study, therefore, effects of bleaching process on the surface roughness of wood was investigated for Lebanon cedar (Cedrus libani A. Rich.) and Black poplar (Populus nigra L.) using the bleaching chemicals NaOH (sodium hydroxide), H2O2 (hydrogen peroxide) and Ca(OH)2 (calcium hydroxide) by the two prescriptions with or without calcium hydroxide.
I Usta, E Aydinlar


Serpula lacrymans – calcium, iron, and foundering wooden boats
2009 - IRG/WP 09-10691
Serpula lacrymans is one of the most destructive wood-degrading brown rot fungi in temperate environments. Its virulence has often been linked to its ability to grow over non-woody materials and extract calcium (Ca) or iron (Fe) to promote wood degradation in buildings. This fungus has also been a severe problem in historic wooden warships and in modern wooden vessels, sometimes leading to foundering (break up) in high seas. In recent work, we have found evidence supportive of the theory that S. lacrymans can translocate and utilize elements from non-woody sources. In the research presented here, we provide data that complement earlier work suggesting that calcium can actually inhibit wood degradation by this fungus, while iron impurities can relieve this apparent stress. Oxalate analysis from agar, as well as SEM-EDS imaging of calcium oxalate crystals and direct hyphal contact with gypsum substrates, suggest calcium may bind oxalate non-productively and may limit its role in iron sequestration. Work by other researchers showing calcium can inhibit oxalate from detoxifying copper and showing supplemental iron may help fungi overcome copper-based preservatives support our observations. These results relate directly to cultural management of this destructive fungal pest and lend mechanistic information on the role of oxalate during brown rot.
J S Schilling, S M Duncan


Protein extraction from wood decay fungus Postia placenta
2014 - IRG/WP 14-10827
Wood decay fungi (often distinguished as white rot and brown rot) belonging to the basidiomycetes, are common inhabitants of forest litter, where they play an important role in carbon cycling. Brown rot fungi are perhaps the most important organism involved in the degradation of wood products, and of considerable economic importance. Brown rotted wood loses strength very early because of the rapid depolymerisation of cellulose. Identification of specific genes and enzymes involved in conversion of lignocellulose is of growing interest not only in the field of wood preservation but also to bioenergy process development. To determine which proteins are being uniquely expressed during the decay process, proteomic profiles can be used to compare fungi growing on different carbon sources, for example untreated wood and modified wood. With a better understanding of the fungal decay mechanisms, wood protection processes and product properties could be further improved and the underlying mechanisms of inhibition or delay of biological degradation in modified wood could be revealed. The aim of this paper was to develop a straight forward method for protein extraction suitable for the filamentous fungus Postia placenta - with low health hazards. We conclude that so far, the most promising method with regard to simplicity and health issues, is a sodium chloride based extraction procedure followed by a precipitation based concentration with trichloroacetic acid (TCA). Another concentration protocol based on filtration is also looking very promising and will be further investigated.
A Pilgård, P Arnold, K Richter


Study on the Effects of Flame Retardant in Dancheong for Korea Wooden Cultural Heritage
2015 - IRG/WP 15-40692
This study identifies the effect of the agent depending on environment change and conducted basic study to prepare criteria for stable application. Dancheong sample, which is similar to wooden cultural heritage, was manufactured to study the effect of the agent on dancheong. Regular observation on the samples located in inland and shoreline area in the country detected visible phenomena. Whitening, melting, peeling were observed, especially whitening was most frequently observed. This can be interpreted that whitening occurs when calcium carbonate reacts to phosphate system, a main ingredient of flame-proofing agent.
Hwa Soo Lee, So Jung Lee, Gyu Seong Han, Yong Jae Chung


Green approach in wood mineralization for improvement of fire properties
2022 - IRG/WP 22-30769
Various treatments have been developed in order to improve fire properties of wood. Because the use of some flame retardants can release toxic compounds in the event of a fire, leading to poisoning or even death of people from smoke inhalation, the use of no-toxic and more ecologically acceptable flame retardants is preferable. Mineralization of wood with the incorporation of carbonates has proven to be a promising method for improving fire properties. The paper presents fire properties of two wood species (spruce and beech) modified using recently proposed eco-friendly mineralization process. Method is based on vacuum pressure impregnation using water solution of calcium acetoacetate which transforms to CaCO3 deep inside the wood structure. The parameters for determining the classification of reaction to fire were investigated. The increase in time ignition, decrease in the total heat release and the fire growth rate index were observed for mineralized wood. Moreover, reduced weight loss in different pyrolysis process of mineralized wood determined by thermogravimetric analysis indicates improved fire performance of such material.
A Pondelak, R Repič, L Škrlep, N Knez, F Knez, A S Škapin