BIOLOGICAL CONTROL OF KILN BROWN STAIN IN RADIATA PINE

Abstract

Kiln brown stain in radiata pine (Pinus radiata) is a chocolate-brown discolouration that forms near the surface of boards dried at high temperature. This stain is the result of a thermochemical reaction between compounds in the sap that accumulate at the surface of the boards during drying. In this study, an attempt was made to remove the compounds that cause the stain, using bacteria in water sprinkled over the boards. Boards were stored in a tank, which was inoculated with rotted woodchips, with a recirculating overhead sprinkling buffer solution. Boards were periodically removed from the tank and dried under conditions that normally produce severe kiln brown stain (120/70°C). Samples were then removed to determine the level of stain by image analysis and the ease of moisture movement by neutron radiography. The bacterial treatment modified the extent of the stain layer so that after about 8 days of treatment there was no noticeable stain. The drying characteristics of the wood were modified so that the boards dried more slowly above fibre-saturation point, although the permeability of the dried wood increased

Keywords

• kiln brown stain
• control
• wood colour
• bacteria