# Spectral Raman Database of Modern Acrylic Paints at 532 nm and 633 nm Laser Excitation Wavelengths
## 3 Results and Discussion
The main Raman features fall at 483 cm\({}^{-1}\), 546 cm\({}^{-1}\), 591 cm\({}^{-1}\), 640 cm\({}^{-1}\), 678 cm\({}^{-1}\), 746 cm\({}^{-1}\), 804 cm\({}^{-1}\), 830 cm\({}^{-1}\), 845 cm\({}^{-1}\), 953 cm\({}^{-1}\), 1008 cm\({}^{-1}\), 1038 cm\({}^{-1}\), 1096 cm\({}^{-1}\), 1144 cm\({}^{-1}\), 1196 cm\({}^{-1}\), 1215 cm\({}^{-1}\), 1308 cm\({}^{-1}\), 1343 cm\({}^{-1}\), 1373 cm\({}^{-1}\), 1413 cm\({}^{-1}\), 1431 cm\({}^{-1}\), 1454 cm\({}^{-1}\), 1472 cm\({}^{-1}\), 1485 cm\({}^{-1}\), 1531 cm\({}^{-1}\), 1593 cm\({}^{-1}\), 1610 cm\({}^{-1}\), 1641 cm\({}^{-1}\), 2188 cm\({}^{-1}\), 2211 cm\({}^{-1}\), 2279 cm\({}^{-1}\), 2677 cm\({}^{-1}\), 2797 cm\({}^{-1}\), 2873 cm\({}^{-1}\), 2984 cm\({}^{-1}\) and 3061 cm\({}^{-1}\). Among all such Raman features, there are vibrational modes attributed to beta phthalocyanine (observed in the Raman spectrum of PBC pigment, see Figure 5) and to sodium polysulfide-aluminosilicate (observed in the Raman spectra of UL pigment, see Figure 15) [15; 20; 39]. As stated above, the different Raman spectra collected by using two laser sources are due to a Resonance effect that improves the detectability of some bands. Figure 7.3 Photograph of Iridescent Silver (IS) pigment **(a)**; optical microscope images of IS pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with green laser of IS pigment on wood (**d**) and on glass substrates (**e**). Figure 23 shows the photograph of the pigment Permanent Blue Light (PBL) (Figure 23a), the optical microscope images of the pigment on wood (Figure 23b) and on glass (Figure 23c), and the Raman spectra collected with the 532 nm (blue line) and the 633 nm (red open circle-line) on the pigment deposited on wood (Figure 23d) and on glass (Figure 23e). The photograph (Figure 23a) shows the blue colour of the pigment PBL and the other optical micrographs (Figure 23b,c) show that the morphology of the pigment is not affected by the substrate. Figure 7.4 Photograph of Cadmium Yellow Medium (CYM) pigment (**a**); optical microscope images of CYM pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with green laser of CYM pigment on wood (**d**) and on glass substrates (**e**). The pigment Permanent Blue Light, PBL, is a mixture of chlorinated phthalocyanines, \(\beta\) phthalocyanines and titanium dioxide. Therefore, the Raman spectra show characteristic Raman features attributed to the phthalocyanines at approximately 483 cm\({}^{-1}\), 594 cm\({}^{-1}\), 681 cm\({}^{-1}\), 747 cm\({}^{-1}\), 777 cm\({}^{-1}\), 955 cm\({}^{-1}\), 1145 cm\({}^{-1}\), 1342 cm\({}^{-1}\), 1452 cm\({}^{-1}\) and 1531 cm\({}^{-1}\)[20; 39]. Of course, as state above, to the Resonance Raman effect is ascribed the reason why the spectra collected with different laser sources show different Raman spectral patterns. The bands assigned to titanium dioxide are detectable at 440 cm\({}^{-1}\) and 588 cm\({}^{-1}\). Figure 24 shows the photograph of the pigment Van Dyke Brown (VB) (Figure 24a), the optical microscope images of the pigment on wood (Figure 24b) and on glass (Figure 24c) and the Raman spectra collected on the pigment deposited on wood (Figure 24d) and on glass (Figure 24e). Figure 7.5 Photograph of Cobalt Blue (Hue) (CB(H)) pigment (**a**); optical microscope images of CB(H) pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with 532 nm laser (blue line) and 633 nm laser (red open circle-line) of CB(H) pigment on wood (**d**) and on glass substrates (**e**). The photograph (Figure 24a) shows the Dark Brown colour of the pigment VB and the other optical microscope images (Figure 24b,c) show that the morphology of the pigment is not affected by the substrate. The pigment Van Dyke Brown, VB, is a mixture of brown iron oxide, carbon black and quinacridone [45].