4 CONCLUSION

Infrared linear mapping microspectroscopy has been found to be a useful technique in the identification of individual layers in multilayered varnish samples. Thin section slices of multilayered cross-section resin samples suitable for infrared microscopic analysis were obtained by the use of embedding and microtoming techniques. Of the many embedding media tested in this study, the polyester type was shown to be the best for furniture varnish layers. Infrared spectra were obtained from analysis of 20 � 400 μm regions of the thin cross-section samples by systematic stepwise movement of sample stage under the apertured analysis window. This process yielded an infrared spectral linear map of each multilayer resin sample that provided information about composition, position, and size of finish layers. The resulting information can be used to elucidate the sequence of layer deposition. In our samples we found that the infrared changes correlated with visually apparent changes in the samples, but it is also possible to use the linear mapping experiment to identify changes in composition that are not visible under the optical microscope.

Future work will be done to examine the effects of aging and refinishing on resin boundaries and surface oxidation. The lateral resolution of infrared microspectroscopy shows potential for the study of surface oxidation and its kinetics during the natural or artificial aging processes. Studies focused on examination of resin-resin interface might produce new data on the stability of the interface during refinishing.

ACKNOWLEDGEMENTS

We would like to thank Frank Preusser for his support of this research. We are grateful to Brian Considine, J.Paul Getty Museum; Robert Mussey, Robert Mussey, Inc.; and Joseph Godla, Society for the Preservation of New England Antiquities, for providing us with samples for analysis.