This work used a multi-analytical approach to characterize two 19th century ambrotypes and was motivated by the lack of insight on these historical objects. Photographic imaging and optical microscopy (OM) were used to identify abrasions, cracks related to reticulation, tarnishing, and other aspects associated to production and degradation processes. With variable pressure scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS) these processes were seen with great detail and further characterized. Elemental point analysis and elemental mapping showed that the photosensitive material used was silver iodide. Degradation compounds were found as silver and chlorine-containing compounds. In one of the items, the tarnishing area also contained redeposited silver in a ring-shape surrounding a nucleus rich in silver, copper, and sulfur, in addition to copper-based salts. EDS analyses also identified that the supports were common soda–lime–silica glasses, refined with arsenic; and showed that a pigment rich in iron was used in both items to hand color the cheeks, extended with aluminum silicates alone or mixed with barium sulfate. The μ-Raman study pointed out that a synthetic Mars pigment was employed. μ-Fourier-transform infrared spectroscopy analyses identified collodion as the binder. Shellac was used as a protective varnish in one of the items and a gum was possibly employed on the other. Bitumen was used for the background in one ambrotype.

This work explores the combination of µ-Raman spectroscopy and scanning electron microscopy with X-ray energy dispersive spectrometry (SEM-EDS) for the study of the glazes in 15th–16th century Hispano-Moresque architectural tiles. These are high lead glazes that can be tin-opacified or transparent, and present five colors: tin-white, cobalt-blue, copper-green, iron-amber, and manganese-brown. They are generally homogenous and mineral inclusions are mostly concentrated in the glaze-ceramic interface. Through SEM-EDS, these inclusions were observed and chemically analyzed, whereas µ-Raman allowed their identification on a molecular level. K-feldspars, wollastonite and diopside were the most common compounds, as well as cassiterite agglomerates that render the glaze opaque. Malayaite was identified in green glazes, and andradite and magnesioferrite in amber glazes. Co–Ni–ferrites were identified in blue glazes, as well as Ni–Fe–olivines. Manganese-brown is the color where most compounds were identified: bustamite, jacobsite, hausmannite, braunite, and kentrolite. Through the µ-Raman analysis of different areas in large inclusions previously observed by SEM, it was possible to identify intermediate phases that illustrate the reaction process that occurs between the color-conferring compounds and the surrounding lead glaze. Furthermore, the obtained results allowed inference of the raw materials and firing temperatures used on the manufacture of these tiles.