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Improvement of liquid penetration of wood by precompression under appropriate conditions and recovery process
1993 - IRG/WP 93-40014
A new system for enhancing the penetration of liquid into wood using a precompression treatment was designed, and the effects of compressive deformation and recovery on liquid uptake were evaluated. Precompression of up to 60% under appropriate moisture and heat conditions effectively increased the penetration of liquid into refractory wood samples of practical sizes without producing any strength reduction. Water-saturated wood was compressed perpendicularly to the grain at temperature of 30 to 80°C, and two types of pretreated wood were prepared; i.e., set-recovered wood in which loading was released immediately after precompression, and preset-fixed wood which was dried under the influence of a decompressive force. The amount of liquid taken up by set-recovered wood was 2-3 times that taken up by untreated wood. When preset-fixed wood was dipped in liquid and the deforming force was released, liquid penetration was more than 25 times that seen in untreated softwood heartwood. Liquid effectively penetrated even long samples when pressure impregnation was applied to precompressed and preset-fixed wood. No significant reduction of strength was observed for treated wood except for that which had been precompressed up to 60%. Fracture of pit membranes during compression with little damage to unpitted cell-walls and an elastic recovery process were believed to improve liquid penetration with negligible compression defects.
I Iida, Y Imamura


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


Raising of the grain and deformation of Scots pine (Pinus sylvestris) treated with water-borne preservatives
1987 - IRG/WP 3456
In Sweden partial impregnation to 10 mm depth of the pine sapwood (class B in the Nordic preservation standard) of joineries was introduced during the seventies. To avoid product quality problems, organic solvent-based systems have been used. However, the Swedish industry today has problems with organic solvents, mainly for environmental reasons. We have studied raising of the grain and deformation of pine impregnated with water-based systems to 10 mm depth of the sapwood. Pine treated with water and the so-called Royal-process has been compared with pine treated with a commercial white spirit-based preservative. For the water-impregnated material we have received approximately the same results as for the Royal-impregnated products. The Royal-process is used in Sweden for windows. Our conclusion is that water-based preservatives could be used for treatment of joinery without product quality problems.
G Hägglund, T Sebring


Step-wise pressure process for reducing surface roughness in Japanese cedar timber
2003 - IRG/WP 03-40256
Sixteen dried sawn-timber (10.5 x 10.5 x 360 cm) were cut into half. The half of them was treated by step-wise pressure process with 2.5 MPa maximum, and the other half was treated by conventional pressure process with 2.5 MPa maximum. Average DDAC preservative absorption was 461 kg/m3 in the former and 525 kg/m3 in the later. Surface roughness was expressed as the profile element height of collapse on the surface of treated timber. The maximum profile element height was 1.10 mm in the former and 3.10 mm in the later. The average value height ranged between 0.35 mm and 0.58 mm in the specimens by conventional process, and 0.19-0.24 mm in those by step-wise process. Step-wise pressure treatment reduced the surface roughness but also reduced preservative absorption.
K Yamamoto, M Nozoki