Your search resulted in 101 documents. Displaying 25 entries per page.
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
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
Strength loss associated with steam conditioning and boron treatment of radiata pine framing
1987 - IRG/WP 3438
The combined effect of included defects and wood moisture content on the strength loss of second rotation radiata pine framing following conventional steam conditioning is investigated. The green Modulus of Elasticity (MOE) is reduced by approximately 13% after steaming. When dried after steaming, however, neither the MOE nor MOR is significantly different from unsteamed dried controls.
M J Collins, P Vinden
The use of pressure cycling to improve heartwood penetration in Pinus radiata (D. Don)
1995 - IRG/WP 95-40050
This study investigates the effect of cycling pressure on the treatability of radiata pine heartwood. The results indicate that liquid penetration into the heartwood is affected by the preconditioning method used and pressure treatment time. There is no significant improvement in the penetration of Pinus radiata (D. Don) heartwood when a cycling or pulsation process is used.
P R S Cobham, P Vinden
Spruce lumber treatments with ammoniacal solutions of inorganic preservatives
1977 - IRG/WP 391
As a part of our work in the Wood Preservation group at the Eastern Forest Products Laboratory in Ottawa to facilitate exploitation of spruce, which is a large timber resource in Canada, we have been studying the treatability of spruce roundwood. A report on this subject was presented to this group last year. More recently, another commodity - spruce timber - has been rapidly gaining the interest of wood treaters, mainly because of its potential use in permanent wooden foundations. We identified this trend and extended our research work to the treatability of spruce lumber.
Borate thermal treatments
1992 - IRG/WP 92-3715
Green, partially seasoned (air-dried, steam conditioned), or kiln-dried southern pine timbers were treated thermally using 15% disodiumoctaborate tetrahydrate solution. After treatment, sections were stored under non-drying conditions to allow for diffusion. Results showed that effective treatment meeting the AWPA minimum retention (0.17 B203 pcf [2.72 kg/m³] in the outer inch) and penetration (2.5-in [64-mm] or 85% of the sapwood) could be obtained only with certain combinations of seasoning, treatment, and diffusion storage. The best results in terms of both retention and penetration were obtained with material steamed and stored prior to treatment using a 10-min hot bath time. Kiln-dried timbers could not be treated effectively. The results suggest that non-conforming treatment of green or partially seasoned timbers will require higher solution concentrations, higher hot bath temperatures, and/or longer diffusion periods to meet required standards. Results also indicated that treatment of smaller stock in dimension sizes (up to 2-in [50-mm]) should be feasible.
H M Barnes, R W Landers, L H Williams
An investigation of the effects of pre-steaming on the treatment of sawn spruce timber with Celcure A, a copper-chrome-arsenic preservative
1981 - IRG/WP 3150
Difficulties in the treatment of spruce using standard vacuum/pressure techniques with both water-borne and organic solvent preservatives are well known. We have evaluated the influence of steaming on treatability with a waterborne CCA preservative.
C R Coggins
Accelerated fixation of CCA in borak bamboo (Bambusa balcooa Roxb.) of Bangladesh
2001 - IRG/WP 01-40193
CCA-C fixation study on impregnated (6% CCA solution), then boiled, oven-dried, normal, air-dried and steamed bamboo slices of air-dried borak bamboo (Bambusa balocca Roxb) of Bangladesh, revealed almost complete fixation in steamed (accelerated fixation) and air-dried (3 weeks, slow fixation) bamboo slices compared to moderate to slow fixation in boiled, oven-dried, normal and 24h air-dried slices.
A K Lahiry
Radical changes in the requirements for more safe pressure impregnation in the Nordic countries in 1988
1990 - IRG/WP 3581
After introduction of quality control schemes and standards in the Nordic countries during the seventies, the first radical change of the standards and practice of work took place after pressure from the labor unions and authorities in 1988 and 1989 in Denmark and in Sweden. A new class of preservation with less retention for out of ground contact use was introduced, fixation times were prolonged to 6 and 14 days, and branding became a requirement. At the same time, treating companies replaced CCA with arsenic-free preservatives, and started using processes for accelerated fixation. Drying of treated wood was started to be used widely.
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
Observations on the failure of anti-sapstain treated timber under non-drying conditions
1990 - IRG/WP 1437
A range of bacteria and yeasts were isolated from antisapstain treated timber and fresh sawdust. Solution samples containing 100 ppm of TCMTB in a nutrient medium were inoculated with these organisms and incubated at 25°C for 5 days. The levels of TCMTB remaining in solution were determined by HPLC analysis after this time. Results indicated high losses of active ingredient for a range of organisms. These results suggest that active biodetoxification of organic biocides could occur in a short period of time during storage of antisapstain treated timber under favourable conditions. The implications of these results are discussed.
G R Williams
Analysing the characteristic role of moisture content for drying and fluid flow in Sitka spruce. - Part 1: The drying process of sapwood and heartwood of two different thickness of Sitka spruce using a kiln. - Part 2: Effects of moisture content on longitudinal permeability of Sitka spruce in vertical variation of the tree
2000 - IRG/WP 00-40173
The characteristic role of the moisture content in Sitka spruce (Picea sitchensis (Bong.) Carr.) that grown in the United Kingdom was examined by this study on the basis of (1) the reduction of moisture content in two different thickness of sapwood and heartwood by kiln drying process, and (2) the effects of moisture content to the longitudinal void volume filled of tanalith-C by the full-cell process from base (1 m) to apex (3 m) of the tree in sapwood zone. Accordingly, conclusions on indication of the drying process of sapwood and heartwood, and vertical variation of longitudinal flow with effects of moisture were listed separately: (1) Comparison of Drying Characteristic of Sapwood and Heartwood: The two different thickness (300x30x30 mm3 and 300x20x20 mm3) of sapwood and heartwood of Sitka spruce was dried using the suggested drying schedule in kiln. The reduction of moisture was schematically diagrammed according to sapwood and heartwood stakes. The reduction of moisture followed the same downward trend that sapwood (S) loses more moisture than heartwood (H) although the small stakes of S and H lost moisture rapidly compared with the large ones. (2) Vertical Variation of Moisture Content and Longitudinal Permeability: The 90 kiln dried defect free sapwood stakes (150x25x25 mm3) of Sitka spruce was taken from base to apex of the trees at 1, 2 and 3 m above ground level. After having the determination of moisture content in each experimental stake, the treatment was carried out by the full-cell process with CCA preservative (Tanalith-C) using a model pressure treatment plant. Significant differences observed among the tree heights from 1 to 3 m showing that slightly increases of moisture content from base to apex and conversely decreases of longitudinal void volume filled by preservative fluid.
Steam conditioning of partially dried radiata and Corsican pine roundwood
1988 - IRG/WP 3499
The effect of partial air drying prior to steam conditioning and its effect on subsequent preservative treatment by the Bethell treatment process was investigated. A high standard of preservative treatment was obtained in both radiata and Corsican pine, irrespective of whether a period of partial drying was imposed before or after steam conditioning.
P Vinden, D R Page, K Nasheri
Water-repellent additive for CCA
1991 - IRG/WP 3655
Hickson have developed a water repellent additive for incorporation into copper-chromium-arsenate timber treatment solutions. The water repellent emulsion shows good stability in the treatment solution, is easily incorporated and applied in a single stage treatment. No modifications to the additive is safe to treatment schedule are usually needed and use. Weathering of the treated wood is substantially inhibited by the presence of the additive. Adhesion of paints is not affected.
P Warburton, R F Fox, J A Cornfield
Survey of conditioning treatment practices in India
1978 - IRG/WP 3127
India has 75.3 million hectares (ie about 24% of total land area) under forests out of which the area of productive forests, from which industrial wood is available, is about 60 million ha. The Task Force on Forest Resources Survey has tentatively estimated that the total growing stock in Indian Forests is 24,000 million cubic metres (m³). The total recorded production of wood in the country is roughly estimated as 25 million m³ annually of which approximately 10 million m³ is demanded by various industries and the remaining is used as fuel. India, with developing economy needs very large resources of timbers for diverse purposes. There is already shortage of timber in the country for various wood based industries and it is expected this will progressively increase with the rapid pace of industrialisation. However, suitable measures are being taken to bridge the gap between demand and supply. The entire 10 m³ of industrial wood requires some sort of protection against wood-destroying agencies. Timber awaiting conversion during storage needs prophylactic treatment while for use as poles, fence posts, sleepers, building material, in cooling towers, boats, ships, in mines, in sea-water, etc., timber should be adequately treated with suitable wood preservatives to obtain satisfactory service life. Both heart and sapwood of non-durable species and only sapwood of durable species need protection against wood-destroying agencies. Wood Preservation on scientific and modern lines was introduced in India by Sir Ralph Pearson of the Indian Forest Service in the year 1908. In India, the first wood preservation plant was established at Bally in Howrah in 1854. Of the total timber extracted in India, only a very small proportion, estimated at about 5% is treated. This amounts to 0.45-0.50 million m³ of wood per annum. The total annual capacity of 140 preservation units, existing in the country at present, is estimated at 0.43 million m³ on single shift basis. IS: 401-1967 (Indian Standard - Code of Practice for Preservation of Timber) covers types of preservatives, their brief descriptions, methods of treatment, and the type and choice of treatment for different species of timber for a number of uses. This standard includes only such preservatives and methods of treatment which have given satisfactory results under Indian condition of service. According to this standard, whatever process of treatment is adopted, timber for treatment should be sound and should be dried to an appropriate moisture content (generally not more than 15% for open tank and 25% for pressure processes). All the wood working etc should be done prior to treatment. In case of timbers, specially some conifers having non-durable heartwood which is refractory to treatment, when treating thick members like railway sleepers, beams, piles, etc, incision of all the surfaces, other than the ends, to a depth of 12-20 mm is necessary.
M C Tewari
Collaborative tests on the influence of solvent and drying method on the toxic limit of wood preservatives against Basidiomycetes
1974 - IRG/WP 248
Seven institutes from five countries, Austria, England, France, Germany and the Netherlands have collaborated in a study on the influences of solvent and drying method on the toxic limits of wood preservatives against Basidiomycetes tested according to the agar-block method. Two preservatives, a 25% pentachlorophenol-concentrate and tributyltinoxide were applied to pine sapwood and beech and tested against Coniophora puteana. The preservatives were diluted with either acetone. benzene, chloroform or xylene. Slow drying in vapour of the solvent was used for all solvents. In addition quick drying was used for benzene and chloroform and freeze drying for benzene. The results were not conclusive regarding any influence of the solvent and drying method on the toxic limit. There was a trend that the toxic limit of the pentachlorophenol concentrate is decreased by the use of acetone as solvent. An influence of acetone on the toxic limit of tributyltinoxide could not be stated. The results regarding an influence of the drying method on the toxic limit of the preservatives were variable. There is some evidence that the toxic limits are lowered by freeze drying. As this effect is not present in all cases, the differences in the established toxic limits are probably due to normal variation in results and not associated with the drying method.
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
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
A new model for wetting and drying of wood end-grain – with implications for durability and service-life
2011 - IRG/WP 11-20477
New experimental data for wetting and drying of wood end-grain, Sandberg (2009), imply that traditional models for moisture transport are not at all applicable. A new model is developed to consider the phenomenological behaviour of water transport in and out of end-grain, using the pore water pressure and sorption scanning properties. Modelling results are compared to experimental results and the consequences for durability are discussed.
L-O Nilsson, K Sandberg
Adequate preservative treatment of tropical and subtropical hardwoods for electric anchor logs
1997 - IRG/WP 97-40101
Most available 27 different hardwood species grown in Bangladesh was investigated regarding suitability as CCA-C (chromated copper arsenate type-C) impregnated anchor logs for rural electrification programme. The kiln-drying properties, sapwood thicknesses, CCA treatability grades of sapwood and heartwood, natural durability of heartwood and CCA retainability at specific assay zone separated 27 hardwoods into two different treatment groups A and B. The logs of both the groups were full cell pressure treated at initial vacuum of 600-700 mm Hg and at impregnation pressure of 14-18 kg/cm2. The logs are equivalent regarding service life. The treatment group A includes 7 species, characterized by pretreatment moisture content of 15%, thin sapwood thickness of at least 25 mm, high natural durability and refractory to treatment of heartwood, penetration requirement of at least 25 mm plus 100% sapwood with treatment grades of 75% (+++) and retention requirement of 20 kg/m3 dry oxides in an assay zone of 5-25 mm. The treatment group B includes 20 species, characterized by pretreatment moisture content of 20% thicknesses of sapwood and treatable wood equivalent to at least 44% of radius of logs, low natural durability of heartwood, penetration requirement of at least equivalent to 44% of radius of logs plus 100% sapwood with treatment grades of 75% to 100% (+++ to ++++) and retention requirement of 20 kg/m3 dry oxides in an assay zone of 12-50 mm.
A K Lahiry
The use of zirconium as an inert fixative for borates in preservation
2001 - IRG/WP 01-30256
Stand-alone borates have been used in internal protected situations as wood preservatives for about 60 years. They have not been deemed acceptable for external situations because of their leaching characteristics. Work carried out to reduce the leachability of borates has been reviewed briefly here, and a specific fixation agent based on zirconium has been tested in standard leaching and decay tests. It was found that the performance of zirconium could be optimized for fixation at specific drying temperatures and at higher formulation pH. Using sufficient quantities of ammoniacal zirconium carbonate and potassium zirconium carbonate such formulations are then able to pass both Standard European and American Wood-Preservers' Association methods designed for testing exterior wood preservatives. Formulations based on borate with a zirconium additive are probably suitable for use in exterior above ground and possibly ground contact situations. As only initial indicative tests have been carried out so far, further testing with a range of wood destroying organisms and field tests should be carried out to evaluate this system further.
J D Lloyd, J L Fogel, A Vizel
Washboard effect: A surface deformation of spruce resulting from vacuum-pressure impregnation with water-borne preservatives
1987 - IRG/WP 3450
The washboard effect has been observed in sawn spruce after both commercial and laboratory based preservative treatments and is of increasing economic importance. The effect is defined as a specific phenomenon at the wood surface. It is distinct from internal collapse in the wood, but it may occur in association with internal collapse damage. Experimental investigations on the causes of washboarding and preliminary results indicate that a combination of several factors induce the effect. At treating pressures below about 10 bar washboarding appears to develop with post treatment drying of the wood whereas with higher pressures it will occur during the impregnation cycle. Further research has been started to develop measures to minimise the problem.
H Willeitner, R J Murphy
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.
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
Artificial drying of impregnated wood
1987 - IRG/WP 3448
Sawn timber (Pinus Sylvestris) of dimension 50x150 mm was impregnated with CCA by a full-cell process. The timber was then dried in a conventional kiln or a special vacuum kiln where the timber was dried by circulating superheated steam. Drying time was 16 days and 2 days respectively. The aim of the investigation was to compare the physical appearence of the wood after drying by the two methods with particular reference to formation of checks. Moisture contents and checks were therefore recorded before and after drying. It was found that the number of checks formed was approximately the same by either drying system and no inner checks were found. The drying in superheated steam, however, caused bleeding of resin on the surface of the wood, which could be a disadvantage for some end uses.