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Figure 11. Comparison of representative Raman spectra from colourless versus naturally coloured Group Ill glasses (left) and colour- less versus coloured Group Ill glasses (right) (Ill-colourless: sample 222-6; Ill-colourless/yellow: sample 215-4; Ill-colourless/grey: sample 215-5; Ill-colourless/pink: sample 215-6; Ill-dark blue: sample 221). The high-lead glass (219-4) has an overall different Raman spectrum, since in this case lead may also act as a network former. Both the v(Q*) and the v(Si-O- Si) bands are broader, as in binary lead-silicate glasses (Feller, et al., 2010) and appear in significantly lower energies than in a typical silica spectrum (at 1072 and 480 cm’', respectively). The spectra of low-lead of the v(Si-O-Si) and v(Q") Raman bands change with chemical composition and certain parameters of glass production technology like firing and/or glass quench- ing conditions (Moncke, 2006), thus allowing the dis- crimination between different glass types. This approach has many significant advantages: the analysis

Figure 11 Comparison of representative Raman spectra from colourless versus naturally coloured Group Ill glasses (left) and colour- less versus coloured Group Ill glasses (right) (Ill-colourless: sample 222-6; Ill-colourless/yellow: sample 215-4; Ill-colourless/grey: sample 215-5; Ill-colourless/pink: sample 215-6; Ill-dark blue: sample 221). The high-lead glass (219-4) has an overall different Raman spectrum, since in this case lead may also act as a network former. Both the v(Q*) and the v(Si-O- Si) bands are broader, as in binary lead-silicate glasses (Feller, et al., 2010) and appear in significantly lower energies than in a typical silica spectrum (at 1072 and 480 cm’', respectively). The spectra of low-lead of the v(Si-O-Si) and v(Q") Raman bands change with chemical composition and certain parameters of glass production technology like firing and/or glass quench- ing conditions (Moncke, 2006), thus allowing the dis- crimination between different glass types. This approach has many significant advantages: the analysis

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Table 1. Basic characteristics of the assemblage of Ottoman glass from Kyparissia. aiming at an initial documentation of their preser- vation state. Overall, the microscopic examination showed limited visual alterations; iridescence was the prevailing corrosion pattern visible in all samples. Non-destructive X-Ray Fluorescence (p-XRF) analysis was applied on all samples using a portable Bruker Tra- cer III SD set up, with a beam diameter of 3 mm; data quantification was made using S1PXRF software and a custom-built calibration curve, created in collaboration with the scientific personnel of Bruker. A detailed description of the calibration curve and the accuracy and precision achieved for the analysis of glass is pro- vided elsewhere (Palamara, et al., 2016). In order to optimise the analytical range, two settings were used: (1) an unfiltered low-energy excitation mode (high vol- tage set at 15 kV and current of 24 A, analyses carried out under vacuum) was used for the analysis of major and minor elements with an atomic number, Z, between 11 and 29; and (2) an AI/Ti filtered (0.012 inches Al plus 0.001 inches Ti) high-energy excitation mode (high voltage set at 40 kV and current of 12 uA) was used for the analysis of minor and trace elements with an atomic number Z > 29. The collection time of each measurement was 300 sec. The samples
Table 1. Basic characteristics of the assemblage of Ottoman glass from Kyparissia. aiming at an initial documentation of their preser- vation state. Overall, the microscopic examination showed limited visual alterations; iridescence was the prevailing corrosion pattern visible in all samples. Non-destructive X-Ray Fluorescence (p-XRF) analysis was applied on all samples using a portable Bruker Tra- cer III SD set up, with a beam diameter of 3 mm; data quantification was made using S1PXRF software and a custom-built calibration curve, created in collaboration with the scientific personnel of Bruker. A detailed description of the calibration curve and the accuracy and precision achieved for the analysis of glass is pro- vided elsewhere (Palamara, et al., 2016). In order to optimise the analytical range, two settings were used: (1) an unfiltered low-energy excitation mode (high vol- tage set at 15 kV and current of 24 A, analyses carried out under vacuum) was used for the analysis of major and minor elements with an atomic number, Z, between 11 and 29; and (2) an AI/Ti filtered (0.012 inches Al plus 0.001 inches Ti) high-energy excitation mode (high voltage set at 40 kV and current of 12 uA) was used for the analysis of minor and trace elements with an atomic number Z > 29. The collection time of each measurement was 300 sec. The samples
Figure 1. Concentration of Na,O versus K,O (left) and CaO versus Al,O3 (right). According to Dungworth et al. (2006) medieval and post-medieval glass can be categorised in four types based on its alkali concentration: (a) Na-rich glass, with Na,O>12 wt% and K,0<5 wt%; (b) K-rich glass, with K,O between 10 and 15 wt% and Na,O < 5 wt%; (c) mixed alkali glass, with intermediate rela- tively high values for both sodium and potassium; and (d) HLLA glass, which is easily differentiated by the overall concentration in alkalis (Na,O + K,0 < 10 wt%). Therefore, the majority of the samples of the pre- sent assemblage are Na-rich, three samples are K-rich Raman was additionally employed in order to exam- ine the connectivity of the silicate glass matrix in detail, and therefore the production technology. Attempts to measure Raman spectra with laser excitation in the vis- ible led to strong fluorescence backgrounds. This
Figure 1. Concentration of Na,O versus K,O (left) and CaO versus Al,O3 (right). According to Dungworth et al. (2006) medieval and post-medieval glass can be categorised in four types based on its alkali concentration: (a) Na-rich glass, with Na,O>12 wt% and K,0<5 wt%; (b) K-rich glass, with K,O between 10 and 15 wt% and Na,O < 5 wt%; (c) mixed alkali glass, with intermediate rela- tively high values for both sodium and potassium; and (d) HLLA glass, which is easily differentiated by the overall concentration in alkalis (Na,O + K,0 < 10 wt%). Therefore, the majority of the samples of the pre- sent assemblage are Na-rich, three samples are K-rich Raman was additionally employed in order to exam- ine the connectivity of the silicate glass matrix in detail, and therefore the production technology. Attempts to measure Raman spectra with laser excitation in the vis- ible led to strong fluorescence backgrounds. This
Figure 2. PCA plot for the samples of Group Ill (Inset: PCA vectors plot). described as lead glass. The primary alkali is potassium, although sodium is also present in relatively high con- centration. As expected for lead glasses, the concen- tration of all other oxides is very low (<0.4 wt%). discussed below. The sample is colourless and clear,
Figure 2. PCA plot for the samples of Group Ill (Inset: PCA vectors plot). described as lead glass. The primary alkali is potassium, although sodium is also present in relatively high con- centration. As expected for lead glasses, the concen- tration of all other oxides is very low (<0.4 wt%). discussed below. The sample is colourless and clear,
Figure 3. Representative XRF spectra for samples of green (left), light blue (centre) and blue colour (right) (samples 218-4, 217-1 and 216-1, respectively).
Figure 3. Representative XRF spectra for samples of green (left), light blue (centre) and blue colour (right) (samples 218-4, 217-1 and 216-1, respectively).
Figure 4. Representative XRF spectra of colourless samples demonstrating high arsenic (left), arsenic and manganese (centre) anc high manganese (right) (samples: 215-2, 215-7 and 216B, respectively).
Figure 4. Representative XRF spectra of colourless samples demonstrating high arsenic (left), arsenic and manganese (centre) anc high manganese (right) (samples: 215-2, 215-7 and 216B, respectively).
Figure 5. Concentration of Na2O and K20 for Na-rich and mixed alkali glasses of the Ottoman assemblage from Kyparissia in con parison with published data.
Figure 5. Concentration of Na2O and K20 for Na-rich and mixed alkali glasses of the Ottoman assemblage from Kyparissia in con parison with published data.
Figure 7. PCA plot for K-rich glasses of the Ottoman assemblage from Kyparissia in comparison with published data (Inset: PCA vectors plot).
Figure 7. PCA plot for K-rich glasses of the Ottoman assemblage from Kyparissia in comparison with published data (Inset: PCA vectors plot).
Figure 8. Comparison of the concentration (in wt%) of major oxides for lead glasses from Kyparissia (sample 219-4) and Britain.
Figure 8. Comparison of the concentration (in wt%) of major oxides for lead glasses from Kyparissia (sample 219-4) and Britain.
Figure 9. Comparison of the concentration (in wt%) of major oxides for glasses with low lead contents (<10 wt%) from Kyparissia and Britain. As was mentioned before, the low lead content that was identified in three samples was not necess- arily added in purpose. In order to check the hypothesis that there was a distinct chemical group with low amounts of added lead, the provenance of the low-Pb samples was examined separately in comparison with other samples of the same period which also present PbO<10 wt% (Figure 9). The majority of the low-lead glasses mentioned in litera- ture belongs to the K-rich type and has very low cal- cium concentrations. However, a single glass from A number of recent studies have focused on exploring the potential of using Raman spectroscopy for the identification of different glass types (Colomban, 2003; Baert, et al., 2011; Ricciardi, et al., 2009; Tournie, et al., 2012). The Raman spectra of silica-based glasses show main bands due to the stretching of Si-O-Si brid- ging bonds, v(Si-O-Si), and the Si-O stretching in Q” silicate units, v(Q”), where Q” indicates a silicate tetra- hedron with n bridging and 4-n non-oxygen atoms (Kamitsos and Risen, 1984). The energy and intensity
Figure 9. Comparison of the concentration (in wt%) of major oxides for glasses with low lead contents (<10 wt%) from Kyparissia and Britain. As was mentioned before, the low lead content that was identified in three samples was not necess- arily added in purpose. In order to check the hypothesis that there was a distinct chemical group with low amounts of added lead, the provenance of the low-Pb samples was examined separately in comparison with other samples of the same period which also present PbO<10 wt% (Figure 9). The majority of the low-lead glasses mentioned in litera- ture belongs to the K-rich type and has very low cal- cium concentrations. However, a single glass from A number of recent studies have focused on exploring the potential of using Raman spectroscopy for the identification of different glass types (Colomban, 2003; Baert, et al., 2011; Ricciardi, et al., 2009; Tournie, et al., 2012). The Raman spectra of silica-based glasses show main bands due to the stretching of Si-O-Si brid- ging bonds, v(Si-O-Si), and the Si-O stretching in Q” silicate units, v(Q”), where Q” indicates a silicate tetra- hedron with n bridging and 4-n non-oxygen atoms (Kamitsos and Risen, 1984). The energy and intensity
Figure 10. Representative Raman spectra from colourless glass of each major group (I: sample 217-4; Il: sample 217-5; Ill: sample 222-6; Ill+low Pb: sample222-7; IV: sample 219-5; High-Pb: sample 219-4).
Figure 10. Representative Raman spectra from colourless glass of each major group (I: sample 217-4; Il: sample 217-5; Ill: sample 222-6; Ill+low Pb: sample222-7; IV: sample 219-5; High-Pb: sample 219-4).
Related topics:
ArchaeologyGeologyOttoman StudiesHistory of Ottoman Art and ArchitectureIslamic GlassGlass archaeologyPost medieval glassOttoman Glass
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