Analysis of the boron content of preservative treated oak and pitch pine heartwood before and after leaching
S McCutcheon, G M Smith, J W Palfreyman, B King
Studies to determine the effects, if any, of a variety of boron formulations on heartwood of English oak and American Pitch pine have been previously reported (King et al (1991)). Small wood blocks were treated, at 10°C or 45°C, with borax, polybor or Boracol 20 for periods of 1 month or 4 months then analysed or continuously leached with tap water for a period of 1 month. Reported results showed minor dimensional changes coupled with some weight loss in most test blocks. The boron contents of all blocks have been analysed by the spectrophotometric method of (Williams (1968)). Although an average of 92% boron was lost many of the treated blocks still retained a protective level of boron (>0.04% B). Boron concentrations left in the leached/treated blocks relate to wood species, block orientation, overall weight loss and type of formulation. The results presented in this paper provide further evidence for the applicability of boron formulations to historic timbers and indicate that even in situations of some moisture movement protection may still be afforded by boron treatments.