11th Hardwood Conference Proceedings

Abstract

Clove (Eugenia carryophyllata) and thyme (Satureja hortensis) essential oils (C-EO, T-EO) have demonstrated their antifungal properties and might be useful in the field of wood conservation for remedial or preventive treatments. The present research aimed at studying the effect of pre-treatments of maple (Acer pseudoplatanus) wood surfaces with alcoholic solutions (10%) of C-EO and T-EO on their colour, subsequent coating with shellac or beeswax and the colour stability of the finished surfaces when exposed to artificial light simulating natural light filtered by window glass. Pre-treatments with essential oils of maple wood caused only small colour changes (E <3) under the experimental conditions. Coating with shellac changed totally the colour of all wood samples (E >30), slightly lower values for those pre-treated with T-EO and higher values for those pre-treated with CEO. The corresponding values for beeswax finishing were much lower, varying in the range 4.00-7.5, with the same trend. The light induced colour changes after 96 h exposure were almost similar for the uncoated wood samples, regardless the pre-treatment with essential oils. The colour changes of the samples pre-treated with T-EO and coated with shellac or beeswax were almost similar or slightly lower compared to those measured for the controls without pre-treatment. Contrarily, pre-treatments with CEO resulted in increased light induced colour changes of the coated surfaces, with about 3 units for shellac and 14 units for beeswax. This might be explained by the photo-induced oxidation of eugenol, the main component of C-EO, resulting in formation of new chromophores with quinoid structures, as supported by FTIR. These changes are more visible through the thinned, nearly colourless beeswax film.