Optical Coherence Tomography of 19th Century Glass: Facts and Phantoms

This paper investigates optical coherence tomography (OCT) as an advanced, non-invasive method for 2D and 3D imaging of the surface and subsurface morphology of glass cultural heritage. The OCT system used is a commercial ThorLabs Ganymede II Fourier domain system with a 930 nm center wavelength, axial resolution of 4-6 mu m, and lateral resolution of about 6 mu m. Results from model alkali silicate glass artificially aged at 90 degrees C and 90% RH allow distinction of real features from artifacts produced by the highly reflective glass, and serve as a basis for interpretation of deterioration phenomena. Analytical results from historical glass artifacts are focused on a group of musical glass flutes created in Paris by Claude Laurent between 1807 and 1848. OCT images are compared to results of destructive analysis of the same samples and objects by scanning electron microscopy with backscattered electron imaging of cross-sections, as well as non-invasive light microscopy and NIR-SWIR fiber optic reflectance spectrometry, the latter of which yields complementary molecular information in terms of water vibrations in hydrated glass.