## 3 Results
### \"Il Casanova\"
Lame and metal threads were also analyzed to inquire why their state of conservation is very different in terms of color change and delamination processes (Figure 4 and Figures S3-S5, Supplementary Materials). The metal foils used as lame or wrapped around fibers or even as solid metal strips were made of Al, or Cu/Zn or Cu/Ag alloys, as reported in detail in Table 5. Both copper-containing foils present signals due to chlorine, whose presence may be ascribed to the atmospheric environment or to the cleaning methods, as already observed for historical metal threads [6; 50] (see Figures S4 and S5, Supplementary Materials). FTIR and/or Py-GC/MS were also applied, as detailed in the following paragraphs, to verify the nature of possible synthetic polymers applied as support of metal foils, or as varnishes/lacquers. The presence of synthetic polymers was suggested both by visual inspection under the OM and SEM morphological analyses. For all samples, the presence of a synthetic layer was verified by FTIR. This finding is consistent with literature data [51], describing 20 th century metal threads made of Al, or Ag or Au blends, lacquered with a synthetic material or even trapped (as a sandwich) between two polyester or Cellophane polymer layers. Samples C8, C9, C10, C12, and C13 all featured a sandwich-like structure (OM and SEM images are provided for sample C10 as an example in Figure 4a-c). The infrared spectrum acquired for sample C8 (Figure 2), from the corset lame fabric, was characterized by a broad band around 1000 cm\({}^{-1}\), less intense and wider than that acquired for sample C2, but still referable to carbohydrates. The spectrum also featured the absorption band typical of carbonyl groups at 1730 cm\({}^{-1}\), while the asymmetric and symmetric stretching of methylene groups (2956-2923 cm\({}^{-1}\) and 28 cm\({}^{-1}\)) show relatively higher intensities with respect to the pure viscose, suggesting the presence of a polyester [9; 52; 53]. Even if the spectra showed the presence of bands compatible with cellulose nitrate, the absence in the pyrolysis products of all the characteristic additives of this materials, such as triphenyl phosphate or diisononyl phthalate, allowed us to exclude the presence of such a material. These bands are, thus, associated to external contamination. The hypothesized co-presence of viscose and polyester was confirmed by the interpretation of the pyrolytic profile. The presence in the Py-GC/MS chromatogram of furural ad furan derivatives (labeled as #3, #6, #11-13 and #15 in Figure 3d) allowed us to identify the polysaccharide material specifically as viscose, while the presence of benzene (#1), toluene (#4), 1,2-dimethylbenzene (#7), styrene (#9), phthalic anhydride (#16), and several plasticizers, with diethyl and bis(2-ethylhexyl) phthalate (#18 and #22) as the most abundant, and the absence of any pyrolysis product associated to other binders, as an alkyld resin, could be related to the pyrolysis of a polyester [49]. The absence of glycerin ruled out the possible presence of Cellophane, a material made of regenerated cellulose in which glycerin is added for softening [54]. The co-presence of polyester and viscose can be interpreted by hypothesizing the use of polyester as embedding material for the metallic foil and the presence of viscose as contamination from the textile background underneath the lame (see the photograph of the corset detail in Figure S3a, Supplementary Materials). The same composition was assessed by FTIR for sample C9 (golden foil in the lace applied on the right side of the neckline) and sample C12 (used in the trimming on the left side of the neckline), both showing a sandwich-like structure where polyester is the embedding material. While for sample C9, the presence of viscose is due to the core of the metal thread, for sample C12, it is most probably due to the sewing thread. Samples C10 and C13, from the volant and the lace applied on the left sleeve, respectively, only contained polyester accordingly to FTIR data, besides the aluminum foil.