Efficacy of shellac-based varnishes for protection of wood against termite, borer and fungal attack

Abstract

The termites, wood decay fungi and insect/marine borers cause immense damage to wood and wood products. Shellac, produced by lac insects, is used in various applications including formulation of varnishes. Shellac based varnishes were tested for their efficacy in protecting wood in terrestrial and marine conditions. Tests were carried out as per BIS Standards using specimens of rubber wood (Hevea brasiliensis). After pre-processing, they were treated with four different types of shellac-based varnishes (V1–V4) adopting three types of treatments. Out of three treatment methods, pressure impregnation was found to be most effective. Out of the four varnishes, stakes treated with V4 was 100 % termite-resistant up to 6 months. With respect to the effectiveness in protection against insect borers, all the four shellac based varnishes were better than control. As regards to marine borer attack in 9 months, while control panels suffered an average internal destruction of 48 ± 39 %, destruction was 37 ± 21 % in V2 panels, 18 ± 11 % in V4 panels, 5 ± 5 % in V3 panels and 2 ± 1 % in V1 panels. Regarding anti-fungal efficacy, V1 showed moderate resistance to wood decay fungi. The results of the study indicate the prospects of utilization of shellac based varnishes for wood protection in terrestrial and marine conditions.