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Lecture Hall ICM - Internationales Congress Center München SPIE Optical Metrology > Optics for Arts, Architecture, and Archaeology VII > Light-Matter Interaction and Nonlinear Optics
12:30-12:50 h | ICM - Internationales Congress Center München ICM Room 12a
Subjects: Optical Measurement Systems / Optical Metrology
Parchments are made from an untanned animal skin, which is preserved by liming, scraping and drying under tension. Parchments are very sensitive to water, which causes in extreme case the denaturation of collagen, its main constituent, to gelatin. We implement polarization-resolved Second Harmonic Generation microscopy (P-SHG) and demonstrate that this quantitative method allows probing the early stages of collagen degradation within parchments in a non-invasive way. Nonlinear optical (NLO) microscopy advantageously provides non-invasive three-dimensional (3D) multimodal imaging of scattering samples with micrometer-scale resolution. Among the collected signals, SHG signals are specific for dense non-centrosymmetric materials and therefore provide a unique structural probe of fibrillar collagen at the micrometer scale. P-SHG allows quantitative determination of the fibrillar collagen organization: main orientation of the collagen fibrils within the focal volume and local disorder. This modality is used for the characterization of modern parchments artificially altered with dry heat. The degradation states of these samples are also determined by using the gold-standard technique: the measurement of the shrinkage temperature by differential scanning calorimetry (DSC). P-SHG appears as a quantitative tool for the determination of the collagen degradation state in a noninvasive way. Based on these results, this approach is used for the investigation of historical parchments from the Chartres’ library, that were exposed to fire and then water as a result of a bombing at the end of the 2nd World War. The visual states of the manuscripts are heterogeneous and P-SHG shows its interest for the local characterization of their conservation states. Moreover, these analyses were also performed to compare restored and unrestored parchments in this collection and the measurements revealed that the restoration performed did not alter the conservation state of the fibrillar collagen within the parchment.