3.1.9. Orange Gouaches

Overall analysis revealed the use of six different orange (O1 to O6) gouaches that contained one or more organic and/or inorganic pigments: PY5, PY10, Permanent Red R (PR4), iron oxides, and lead chromate. O1 is a bright orange that contained PY5 and PR4 both confirmed by FTIR [17] and Raman [51] analysis. The light Orange 2 and Orange 3 have similar tonalities, and both contained PY5 and PY10 as confirmed by FTIR and Raman analysis. O2, however, also contained a small amount of lead chromate and a significant amount of gypsum. The composition of O3 was the same as Y2, but the ratio of the PY10 (reddish yellow) to PY5 (greenish-yellow) was reversed based on the intensity of their respective bands in the Raman spectra. Orange 4 and Orange 5 contained ochre, a natural iron oxide pigment rich in kaolinite [52], as confirmed by p-XRF (Al, Si, K, Fe) (Figure S22), r- and μ-FTIR [34], and confocal Raman [31] (Figure S23a). Orange 6 had a more complex composition and contained PY5, PR4 detected by FTIR and Raman analysis of the samples (Figures S24–S26), possibly a small amount of lead chromate based on the p-XRF analysis, Mars Red [31] (Figure S23b) and a second iron oxide pigment (214, 252, 304, 402, 463, and 560 cm<sup>−</sup>1), the latter two detected by confocal Raman.
