Publication details
Laser-induced breakdown spectroscopy in the study of degraded glass mosaics
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| Year of publication | 2017 |
| Type | Conference abstract |
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| Description | Laser-Induced Breakdown Spectroscopy (LIBS) is a technique providing information on elemental composition of the sample using layer-by-layer ablation and subsequent analysis. Samples of degraded blue glass tesserae, which probably represented the original (Gothic) pieces covering the surface of the mediaeval statue of Madonna from Malbork Castle, Poland, before its destruction at the end of World War II., were analyzed using two different LIBS devices. Thirty laser shots were applied to one point and individual spectra were obtained for each shot. Significant elemental lines from spectra acquired by both instruments were chosen and processed to create the depth profiles of the samples. Calibration of the depth profile was performed applying 5, 10, 15, 20, 25 and 30 shots and measuring the depth of the craters using a profilometer. Determining the behaviour of significant elements in the depth profile together with the calibration allowed examination of the thickness of the corrosion layer. Based on the depth profile of potassium it was confirmed that the corrosion layer reaches a maximum of 100 um, which exactly corresponds to the thickness of the visible corrosion layer on the sample cross-section observed in the scanning electron microscope (SEM). From a methodological point of view, it is important that the LIBS method can be applied directly to the surface of the mosaic with no need of sampling and cutting the sample for microscopic studies. Further, LIBS proved to be a suitable method for a ditermining of very low contents of cobalt (not captured by SEM-EDS), which is an intense ionic dye, commonly found in early Gothic glasses. Its concentrations are usually only slightly elevated above the background level and could only be determined by suitable analytical methods, as, e. g. ICP-MS (in the case of the mediaeval mosaic of the Last Judgement in Prague) or XRF and/or LIBS (in the case of the Malbork's Madonna). Materials research of mediaeval mosaics in northern Poland helped to answer the question of their origin. The composition of the glass batch and other additives is closer to German/Prussian productions than to Bohemian ones. |
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