The effect of glycol additives on diffusion of boron through Douglas-fir
C M Freitag, R Rhatigan, J J Morrell
Boron is highly effective against a variety of fungi and insects and is able to diffuse with moisture through wood. Diffusion decreases sharply at lower moisture contents, a characteristic that limits the potential use of this material as a remedial treatment for arresting internal decay. One approach to improvi ng boron diffusion is the simultaneous addition of glycol, which is presumed to enhance boron diffusion. In this study, the potential effects of glycol addition were explored by adding glycol plus boron (Boracol 20®, Boracol 40® or BoraCare®) or Timbor® and fused boron (Impel rods®) to produce a desired boric acid equivalent in each pole. Boron movement was assessed by periodically removing increment cores for chemical analysis. All of the supplements improved the diffusion of boron through Douglas-fir wood. Timbor®, which does not contain glycol, resulted in the most even distribution of boron throughout the poles while Boracol 40® seems to have increased boron diffusion to the point of loss from the poles.