# Spectroscopic and Microscopic Characterization of Flashed Glasses from Stained Glass Windows
## 4 Conclusions  
Flashed glasses, constituted by two layers, one of a colorless glass with a thin colored layer applied on top, have been structurally and compositionally analyzed by optical microscopy, field emission scanning electron microscopy, and linear energy dispersive spectroscopy to determine the thicknesses of the colored layers. The elemental composition of the base glasses and their corresponding-colored layers was determined by laser-induced breakdown spectroscopy and field emission scanning electron microscopy-energy dispersive spectroscopy. Laser-induced fluorescence and UV-Vis-IR spectroscopy provided further information about the chemical nature of the base glasses and colored layers, signposting the presence of the main chromophores responsible for their colors. Laser-induced breakdown spectroscopy results allowed, in a micro-invasive way, the detection of light, major, minor, and trace elements, both in the base glasses and colored layers, with higher sensitivity for major and minor components as compared with the destructive cross-sectional technique of field emission scanning electron microscopy-energy dispersive spectroscopy, which in turn can yield valuable information on chronology, provenance, and manufacturing processes and adds extra value to studies in these type of glasses. Laser-induced breakdown spectroscopy has been revealed as a powerful technique to determine the elemental composition and to look for chemical differences or similarities in the composition of non-destructible samples with historical and heritage value. The speed of analysis achieved with this technique, added to the development and production of portable devices, facilitates the examination of a large number of samples in the field, at excavation sites, in museums, cathedrals, and other civil buildings. Finally, the combination of laser-induced fluorescence and UV-Vis-IR spectroscopy has been revealed to be very effective for the determining of the nature of chromophores responsible for glass coloration.  
Conceptualization, T.P. and M.O.; Methodology, M.O. and T.P.; Formal Analysis, T.P., M.M.-W., M.A., L.M.-G., M.C. and M.O.; Samples' preparation, T.P.; Writing--Original Draft Preparation, T.P. and M.O.; Writing--Review and Editing, T.P., M.M.-W., M.A., L.M.-G., M.C. and M.O.; Project Administration, M.C.; Funding Acquisition, M.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research has been funded by the Spanish State Research Agency (AEI) through project PID2019-104124 RB-100/AEI/10.13039/501100011033, the Fundacion General CSIC (ComFuturo Programme), by project TOP Heritage-CM (S2018/NMT-4372) from Community of Madrid, and by the H2020 European project IPERION HS (Integrated Platform for the European Research Infrastructure ON Heritage Science, GA 871034).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** This study did not report any supplementary data.  
**Acknowledgments:** All authors acknowledge support from CSIC Interdisciplinary Platform \"Open Heritage: Research and Society\" (PTI-PAIS) and [PERSON] for supplying the glass samples.  
**Conflicts of Interest:** The authors declare no conflict of interest.