# Spectroscopic and Imaging Analyses on Easel Paintings by [PERSON]
## 3 Results
### Pigments and Dyes  
#### 3.3.1 Blue and Violet Hues  
Vis-RS analysis allowed the first reliable characterization of the pigments used in the blue and violet areas; depending on the hues, azurite (Cu\({}_{3}\)(CO\({}_{3}\))\({}_{2}\)(OH)\({}_{2}\)) or natural ultramarine (Na\({}_{7}\)Ca(Al\({}_{6}\)Si\({}_{6}\)O\({}_{24}\))(SO\({}_{4}\))(S\({}_{3}\)) \(\cdot\) H\({}_{2}\)O) was mixed with variable amounts of lead white ((PbCO\({}_{3}\))\({}_{2}\) \(\cdot\) Pb(OH)\({}_{2}\)) to increase the opacity of the colour [15]. The precious natural ultramarine, derived from lapis lazuli stone, can be easily detected by vis-RS because of the typical absorbance band of lazurite around 590-600 nm (Figure 2(a), solid lines) and the strong increase of reflectance in the red-NIR spectrum [16]. This blue pigment cannot be unambiguously and directly revealed by ED-XRF due to the low sensitivity of the instrument to the light elements typical of the lazurite mineral (Al, Na, Si). Figure 2: IR reflectography: (**a**) the _[PERSON]_, Clio, detail of the dress with outline underdrawing; (**b**) _[PERSON]_ altarpiece, [PERSON]’s mantle, detail with parallel hatching underdrawing. Natural ultramarine is the prevalent blue found in _Sacred Conversation_ of [PERSON] (GSMF 1, 4, 29, 34, 36) (Figure S1a,b; Table S1), _[PERSON]_ (GSST 1, 17, 18, 34), _Muses_ (MC 1, 11, 17-18, 23-24), _[PERSON] administers the Communication to [PERSON]_ (CRISP 2) and _[PERSON] and the Archaegal [PERSON]_ (GSS 29-32). Azurite was detected because of the typical vis-RS absorbance band around 630-640 nm (Figure 3a, dashed lines). This blue pigment is the one found in the _Sacred Conversation_ of Gradara (GRAD 1, 11-13) and Fano (GSMF 1, GSMF 10, GSMF 25), and _the Martydrom_  
Figure 3: (**a**) Vis-RS spectra of the blue hues of the _Annunciation_ and _Holy Martyr_: comparison between natural ultramarine (solid lines) and azurite (dashed lines). The reference spectra measured on standards (pigments bound in sicactive oil) are displayed in red. Digital micrographs (220\(\times\)): _Holy Martyr_: (**b**) blue sky, azurite, (**c**) blue cloud, natural ultramarine; _Annunciation_: (**d**) [PERSON]’s cloak, natural ultramarine, (**e**) pale blue vase, azurite. of [PERSON]_ (GSM 5, 10), (Table S1). In the _[PERSON]_ altarpiece (GSPB 12-13, 23, 27), the blue areas are painted with azurite (Figure S1c,d) except for the [PERSON]'s band (GSPB 11 bis), made of ultramarine blue (Table S1). According to vis-RS and ED-XRF analyses (Table S1), azurite was mixed with lead white to obtain the sky of the _Holy Martyr_ (GSSR 22) (Figure 3a,b). Probably, the blue shade of clouds (GSSR 20-21; Figure 3a,c) and the sea (GSSR 106) was, conversely, obtained by overlapping natural ultramarine on the azurite layer. In the [PERSON]'s mantle of the _Annunciation_ (GSA 7-8) and in the sky shading (GSA32 bis-33 bis), ultramarine was identified in the upper layer by vis-RS, while Cu was detected by ED-XRF (Figure 3a,d), indicating a double layering too [17]. The data support the hypothesis that the same technique was used in the sky shading and the mountains of _Saint Roch_ (SR 1-2, 4). Natural ultramarine was detected in the far mountains (GSA 27) and [PERSON]'s globe (GSA 34 bis), while azurite was identified in the peculiar blue hue of the vase (GSA 31; Figure 3e; Table S1). The natural ultramarine pigment was mixed or overpainted with a coccid-derived red lake (such as kermes or some European cochinel), sometimes brightened with lead white, to create violet hues (Table S2). This is the case of the shoes (MC 5) and the robe of the _[PERSON]_ (MC 34); the shadow of the mantle (GSST 2) and the book of the _Apostles_ (GSST 35); and several figures' clothes of the _Sacred Conversation_ of Montefiorentino and the angel of the _Annunciation_ (Figure S2a-c). In _[PERSON] and the Archangel [PERSON]_, the red lake was sometimes mixed with ultramarine blue (GSS 11) and sometimes with azurite (GSS 5).