Reflected ligth microscopy as a non-invasive identification tool for wooden artefacts

Species identification is a crucial step in the study of wooden artefacts, but sampling is frequently impossible. The objective of this study is to evaluate the efficacy of reflected light microscopy, including the use of polarising and narrow-band blue filters, as a non-invasive identification tool. Different surfacing and finishing techniques copying historical manufacturing methods were applied to selected species. The visibility of anatomical features was evaluated on the basis of a four level scale. Two indexes were created: an Identifiable Anatomical Features index (IAF) to evaluate the effect of treatments on the complex of microstructural characters, and a Feature Recognition Index (FRI) to estimate the susceptibility of each anatomical feature towards different treatments. Surfacing affected the visibility of anatomical features to different degrees of severity depending both on the technique used and on the species. The visibility could be partially improved or decreased by the presence of finishes, depending on their transparency. Each anatomical feature showed different susceptibilities towards treatments. Both polarising and narrow-band blue filters considerably increased visibility of several anatomical features. Possibilities to recognise individual character states were encouraging, except when obscured by low transparency finishes. Much diagnostic anatomical information can be obtained by the use of non-invasive, reflected light microscopy, although the step from feature recognition to species identification may still require further analysis.