**4. Discussion**

Through the analytical investigation of the St Theodoros icon, authors were able to identify the employed painting materials (except of the organics) and techniques, and now, a crucial question arises: how can these data contribute towards the assessment of painter's identity? To this end, the analytical data were compared to the findings of previous studies of Angelos' known (signed) works [10–12,14,15], and evaluated in the light of analytical investigations of other high-quality Cretan icons [31,37–39]. It is thus shown that the icon in consideration can indeed be assigned to Angelos.

According to the pertinent studies, Angelos' works show a series of specific technical characteristics, that when seen as a whole constitute a rather idiomorphic painting manner. In detail, the gypsum grounds contain always a bit of charcoal and ochres [11,32] (probably added for the purpose of modifying the gesso color) and this is also the case for the St Theodoros icon (Figure 3a), though the incorporation of pigments in grounds is an uncommon practice for post-Byzantine painting [39,40]. As for the gilded backgrounds, Angelos always used a yellow bole substrate to apply the gold leaves on [10,11,15], and yellow is the bole of the St Theodoros icon as well (Figure 5a). Yet, it seems that the red-colored boles were extensively used during 15th century [38], and, hence, the employment of a yellow bole is a very important component of Angelos' 'fingerprint'.

Angelos' palette comprised of 11 pigments, including common ones such as charcoal, ochres and green earth, as well as some valuable and less frequently used ones, such as lazurite and azurite [10,11,13,15]. At first sight, it appears that there is no relevance between this palette and the idiomorphic character of Angelos' paintings. However, the use of natural ultramarine deserves special attention. It is well known that this very pigment was circulating in various grades, the best of which possessed an extremely high cost [24,41]. As is evident by the photomicrographs in Daniilia et al. [11], Angelos' paintings bear first-grade lazurite with grains that usually measure above 10 microns, and this is also the case for the St Theodoros lazurite (Figure 3b). On the other hand, previous analytical studies have shown that lazurite was rather rarely employed in icon painting [29,31] and this indeed adds much value to the identification of ultramarine in the St Theodoros icon. hence, the employment of a yellow bole is a very important component of Angelos' 'fingerprint'. Angelos' palette comprised of 11 pigments, including common ones such as charcoal, ochres and green earth, as well as some valuable and less frequently used ones, such as lazurite and azurite [10,11,13,15]. At first sight, it appears that there is no relevance between this palette and the idiomorphic character of Angelos' paintings. However, the use of natural ultramarine deserves special attention. It is well known that this very pigment was circulating in various grades, the best of which possessed an extremely high cost [24,41]. As is evident by the photomicrographs in Daniilia et al. [11], Angelos' paintings bear first-grade lazurite with grains that usually measure above 10 microns, and this is also the case for the St Theodoros lazurite (Figure 3b). On the other hand, previous analytical studies have shown that lazurite was rather rarely employed in icon painting

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the gypsum grounds contain always a bit of charcoal and ochres [11,32] (probably added for the purpose of modifying the gesso color) and this is also the case for the St Theodoros icon (Figure 3a), though the incorporation of pigments in grounds is an uncommon practice for post-Byzantine

5a). Yet, it seems that the red-colored boles were extensively used during 15th century [38], and,

On the other hand, Angelos' paintings show some idiomorphic technical characteristics that resulted in the typical extremely skillful manner detected by archaeologists. In detail, Angelos always rendered the preliminary drawing/sketch by combining thin brushstrokes and very shallow incisions [10,12]. Sometimes the incised drawing could be rather extensive [15]; however, the facial features and the details of flesh and hair parts were always rendered by thin and extremely skillful brushstrokes, they were never incised [10,12,15], and this is regarded a typical characteristic of Angelos' work [14]. Therefore, the fact that the same technique has been applied in the St Theodoros icon is regarded as a notable clue towards assigning the icon to Angelos (Figures 2 and 6b). For comparison purposes, we present an example of preliminary drawing on another high-quality Cretan icon. The artifact in consideration (which is of a slightly later date, i.e., the early 16th century) is the left wing of a Royal Doors pair depicting the Annunciation of Virgin Mary that is currently on display at the Byzantine Museum of Ioannina (BMI), Greece (Figure 7a). In this case, the preliminary drawing incisions are considerably deeper than those of St Theodoros icon (~90 µm/Figure 7b versus ~20 µm/Figure 2d, respectively), while the facial characteristics and hair details are pronouncedly incised (Figure 7c). [29,31] and this indeed adds much value to the identification of ultramarine in the St Theodoros icon. On the other hand, Angelos' paintings show some idiomorphic technical characteristics that resulted in the typical extremely skillful manner detected by archaeologists. In detail, Angelos always rendered the preliminary drawing/sketch by combining thin brushstrokes and very shallow incisions [10,12]. Sometimes the incised drawing could be rather extensive [15]; however, the facial features and the details of flesh and hair parts were always rendered by thin and extremely skillful brushstrokes, they were never incised [10,12,15], and this is regarded a typical characteristic of Angelos' work [14]. Therefore, the fact that the same technique has been applied in the St Theodoros icon is regarded as a notable clue towards assigning the icon to Angelos (Figure 2 and Figure 6b). For comparison purposes, we present an example of preliminary drawing on another high-quality Cretan icon. The artifact in consideration (which is of a slightly later date, i.e., the early 16th century) is the left wing of a Royal Doors pair depicting the Annunciation of Virgin Mary that is currently on display at the Byzantine Museum of Ioannina (BMI), Greece (Figure 7a). In this case, the preliminary drawing incisions are considerably deeper than those of St Theodoros icon (~90 μm/Figure 7b versus ~20 μm/Figure 2d, respectively), while the facial characteristics and hair details are pronouncedly incised (Figure 7c).

**Figure 7.** (**a**) Royal Doors, BMI, detail of Archangel Gabriel, left wing. (**b**) Background image: deep preliminary drawing incision (~91 microns) BSE, 500×. Insert picture: same sample under OM, 100×. (**c**) Detail of Archangel Gabriel face, sketch incisions on the facial characteristics are evident. **Figure 7.** (**a**) Royal Doors, BMI, detail of Archangel Gabriel, left wing. (**b**) Background image: deep preliminary drawing incision (~91 microns) BSE, 500×. Insert picture: same sample under OM, 100×. (**c**) Detail of Archangel Gabriel face, sketch incisions on the facial characteristics are evident.

What is more, the St Theodoros icon shows notable similarities to the Angelos' works as regards the pigment mixtures and paint layer stratigraphy/application methods employed to render specific pictorial elements. In order to highlight the importance of this aspect, it should be kept in mind that the art of Eastern Orthodox iconography is based on a series of rules and dictations that more or less define the materials and techniques to be used when painting an icon. For instance, there are several What is more, the St Theodoros icon shows notable similarities to the Angelos' works as regards the pigment mixtures and paint layer stratigraphy/application methods employed to render specific pictorial elements. In order to highlight the importance of this aspect, it should be kept in mind that the art of Eastern Orthodox iconography is based on a series of rules and dictations that more or less define the materials and techniques to be used when painting an icon. For instance, there are several post-Byzantine painting manuals that offer detailed recipes for the preparation of specific underpaint colors and the corresponding lighter tones [17,42]. Hence, the materials and techniques 'fingerprint' of a Late-Byzantine or Early Post-Byzantine icon painter cannot contain too many unusual features.

In the flesh parts, Angelos used a preparatory paint layer (underpainting/"proplasmos") consisting of yellow ochre, cinnabar, hematite, lead white and charcoal, that was freely applied onto the ground artistic periods of Angelos.

unusual features.

in the form of thin layers [10,11]. It is worth mentioning that the latter rarely exceed 25 µm in thickness [10,13], and that the freehand application of this underpainting is a characteristic that is documented on all Angelos icons [10]. In case of the St Theodoros icon, IR photography (Figure 2) revealed that the flesh underpainting was applied with an identical manner to the one seen on Angelos' paintings. In addition, the cross-section of a corresponding microsample (St Theodoros left hand) shows intriguing similarities in the stratigraphy and composition level with flesh samples from Angelos' icons [10,11,13]. The underpainting in St Theodoros flesh consists of yellow ochre, cinnabar, red ochre, lead white, charcoal and a bit of green earth (Figure 8a). Older studies of Angelos paintings had failed to spot green earth in flesh underpaints, thus leading some scholars to conclude that this is a notable deviation of Angelos from his contemporary painting trends [10]. Nevertheless, this pigment was recently identified in a genuine Angelos icon [13] and in the icon studied herein, implying thus that some parts of the full spectrum of Angelos materials and techniques might still be unknown; in addition, certain features might be specific to particular artistic periods of Angelos. Finally, in order to highlight the rather idiomorphic character of Angelos' flesh painting manner (which is documented in the St Theodoros icon), the icon discussed herein was compared to a relevant high-quality Cretan icon (Annunciation, royal doors, Figure 7). Cross-sections from flesh parts of the two works are shown in Figure 8. The layered structure of St Theodoros sample (Figure 8a) is practically identical to the stratigraphy seen in samples from several Angelos paintings (see for instance the figures in row "a" of Table 1, pages 102–103 in [10]). The characteristic features in both cases (St Theodoros icon and signed Angelos paintings) are the following: (a) the thinness (usually ~20 μm) and color of the underpainting (pale yellowish-brown); (b) the consistent addition of cinnabar in the latter; and (c) the application of only one—yet significantly brighter—middle tone (lead white + cinnabar + ochre) on the base color. The final touches/highlights consist of pure lead white and are applied directly on the middle tone [10,13]. In contrast, the sample from the Annunciation icon shows an underpainting of moderate thickness (~35 μm) that contains no cinnabar (Figure 8b), while the lighter flesh tones were built with at least two brighter (containing more lead white) paint layers (only the first is shown in Figure 8b).

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post-Byzantine painting manuals that offer detailed recipes for the preparation of specific underpaint colors and the corresponding lighter tones [17,42]. Hence, the materials and techniques 'fingerprint' of a Late-Byzantine or Early Post-Byzantine icon painter cannot contain too many

In the flesh parts, Angelos used a preparatory paint layer (underpainting/"proplasmos") consisting of yellow ochre, cinnabar, hematite, lead white and charcoal, that was freely applied onto the ground in the form of thin layers [10,11]. It is worth mentioning that the latter rarely exceed 25 μm in thickness [10,13], and that the freehand application of this underpainting is a characteristic that is documented on all Angelos icons [10]. In case of the St Theodoros icon, IR photography (Figure 2) revealed that the flesh underpainting was applied with an identical manner to the one seen on Angelos' paintings. In addition, the cross-section of a corresponding microsample (St Theodoros left hand) shows intriguing similarities in the stratigraphy and composition level with flesh samples from Angelos' icons [10,11,13]. The underpainting in St Theodoros flesh consists of yellow ochre, cinnabar, red ochre, lead white, charcoal and a bit of green earth (Figure 8a). Older studies of Angelos paintings had failed to spot green earth in flesh underpaints, thus leading some scholars to conclude that this is a notable deviation of Angelos from his contemporary painting trends [10]. Nevertheless, this pigment was recently identified in a genuine Angelos icon [13] and in the icon studied herein, implying thus that some parts of the full spectrum of Angelos materials and

**Figure 8.** (**a**) Sample from the flesh section of St Theodoros, cross-section. Background image: BSE, 2000×; perpendicular line marks the underpainting that contains numerous cinnabar grains (bright particles). Insert picture: same sample, OM, 200×. (**b**) Sample from the Annunciation icon, flesh part. Background image: BSE, 2000×. The perpendicular line marks the underpainting, note the absence of cinnabar. Insert picture: same sample under OM, 200×. **Figure 8.** (**a**) Sample from the flesh section of St Theodoros, cross-section. Background image: BSE, 2000×; perpendicular line marks the underpainting that contains numerous cinnabar grains (bright particles). Insert picture: same sample, OM, 200×. (**b**) Sample from the Annunciation icon, flesh part. Background image: BSE, 2000×. The perpendicular line marks the underpainting, note the absence of cinnabar. Insert picture: same sample under OM, 200×.

Finally, in order to highlight the rather idiomorphic character of Angelos' flesh painting manner (which is documented in the St Theodoros icon), the icon discussed herein was compared to a relevant high-quality Cretan icon (Annunciation, royal doors, Figure 7). Cross-sections from flesh parts of the two works are shown in Figure 8. The layered structure of St Theodoros sample (Figure 8a) is practically identical to the stratigraphy seen in samples from several Angelos paintings (see for instance the figures in row "a" of Table 1, pages 102–103 in [10]). The characteristic features in both cases (St Theodoros icon and signed Angelos paintings) are the following: (a) the thinness (usually ~20 µm) and color of the underpainting (pale yellowish-brown); (b) the consistent addition of cinnabar in the latter; and (c) the application of only one—yet significantly brighter—middle tone (lead white + cinnabar + ochre) on the base color. The final touches/highlights consist of pure lead white and are applied directly on the middle tone [10,13]. In contrast, the sample from the Annunciation icon shows an underpainting of moderate thickness (~35 µm) that contains no cinnabar (Figure 8b), while the lighter flesh tones were built with at least two brighter (containing more lead white) paint layers (only the first is shown in Figure 8b).
