Table 1 Summary of the results obtained from different analytical techniques employed to study the samples
Sample | Colour | Optical observation | ESEM–EDAX | μ-Raman | FTIR–ATR |
|---|---|---|---|---|---|
Painted fragment | Dark blue | - Thickness =150-250 μm. | Si, Ca, Cu, S, Fe, Al, Mg | * | Cuprorivaite |
- Under reflected light: coarse heterogonous crystals (30 μm in length) with dark blue colour are observed. | Quartz | ||||
Gypsum | |||||
Calcite | |||||
Pigment | Light blue | - Thickness = 100-200 μm. | Si, Ca, Cu, S, Fe, Al, Mg | * | Cuprorivaite |
- It appears as pale blue probably due to the white binding medium (gypsum). | Quartz | ||||
Gypsum | |||||
Pigment | Green | - Thickness = 150-200 μm | Si, Ca, Cu, S, Fe, Al, Mg | * | Cuprorivaite |
- Dark blue and yellow grains are observed, black grains can be seen in some areas. | Quartz | ||||
Goethite | |||||
Kaolinite | |||||
Painted fragment | Dark red | - Thickness = 50-70 μm | Si, Ca, S, Fe, C, Al, K, Mg | Haematite | Haematite |
- Several voids are spread on the surface and black grains are found. | Anatase | Quartz | |||
Carbon | |||||
Kaolinite | |||||
Gypsum | |||||
Paint flake | Yellow | - Thickness = 30 μm. | Si, Ca, S, Fe, Al, K, Mg | Goethite | Goethite |
- The surface is slightly compact with red and black grains within the paint layer. | Carbon black | Gypsum | |||
Quartz | |||||
Kaolinite | |||||
Painted fragment | Black | - Thickness = 30-70 μm. | C, Si, Fe, Ca, S, Cl, Na, Al, Mg, K, Ti | Carbon black | Carbon |
Quartz | Quartz | ||||
Gypsum | |||||
Preparation layer | White | - Thickness = 100-200 μm. | S, Ca, Si, Al, Mg | Gypsum | Gypsum |
Quartz | |||||
Plaster layer | Creamy | - Thickness = 2–4 mm. | S, Ca, Si, Al | Gypsum | Gypsum |
- The sample filled with angular particles. | Quartz | Anhydrite | |||
Calcite | Quartz | ||||
Calcite |