Clarocit

The surface roughness was analyzed using interferometry (White light interferometer, Smart WLI‐extended optical 3D surface Measuring system; GBS) on three specimens from each group before ceramic veneering. Three measurements were made on each specimen. The arithmetic mean height (S_a), developed interfacial area ratio (S_dr), and density of summits (S_ds) parameters were chosen for analysis (Wennerberg & Albrektsson, 2000 (link)).
Another four specimens from each group were analyzed for presence of an α‐case layer. The specimens were sectioned (Secotom‐60; Struers) and mounted by using resin (ClaroCit; Struers) in a purpose‐built brass holder. Grinding and polishing was performed using a semi‐automatic machine (Planpol; Struers). All specimens were etched for 2 min with a solution containing 100 ml distilled H₂O, 3 ml concentrated HCl, and 6 ml concentrated HNO₃. The sample surfaces were rinsed in ethanol and air blown dry before coating with a AU85Pt15 alloy, approximately 5 nm in thickness. Scanning electron microscopy (SEM) was performed at 10 keV (TM4000plus; Hitachi). The specimens were imaged at 500x, 1000x, and 2000x magnification.

Micro-samples of polychromy could only be taken from Christ the Saviour from Death. The first micro-samples were fixed in methyl methacrylate resin (Clarocit, Struers GmbH, Willich, Germany). When hardened, the cross-section was ground and polished and subsequently analysed in a non-destructive manner. The last sample of the surface glaze was taken for the GC-MS analysis. In the case of this sample, the investigation focused solely on the surface glaze layer.

For the light microscopy, electron microscopy, Raman spectroscopy, and indentation studies, the samples were embedded in an acrylic cold mounting resin (ClaroCit, Struers), sectioned using a diamond saw IsoMet 4000 (Buehler), ground with P4000-grade SiC paper, and finally polished with 1 and 0.25 μm colloidal solution. For the surface treatments used for electron microscopy purpose (Fig. 4c), the polished sections of the samples were etched with a solution of 8 M Urea and 5% acetic acid for ~8 min.