Study by grazing incident diffraction and surface spectroscopy of amalgams from ancient mirrors

Abstract

Characterization of four amalgam surfaces, with different alteration degrees from Andalusia historical mirrors, has been carried out by grazing-incidence X-ray diffraction (GIXRD), and other spectroscopic techniques (SEM/EDX, XPS, and REELS). The combination of all these techniques allows determining the corrosion state of the amalgams. The results show that the amalgams are composed in all cases of a binary alloy of tin and mercury. As mercury has high vapour pressure at RT, it slowly segregates and eventually evaporates, it leaves finely divided particles of tin that easily can be oxidize, forming tin monoxide (SnO) and tin dioxide (SnO 2 ). In one of the samples, most of the amalgam remains unoxidized, since Hg 0.1 Sn 0.9 and metallic Sn phases are the major components; in two other samples, Hg 0.1 Sn 0.9 and Sn phases are not detected while SnO 2 and SnO phases appear. Finally, in the last studied sample, only SnO 2 phase is detected. The surface analyses of these samples by XPS show that, for most of them an unique chemical species (Sn 4+ ) is found.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.

Investigation on corrosion morphology and products of ancient tin amalgam mirrors by AFM, SEM–EDS and micro-Raman spectroscopies

“…SEM pictures in Fig. 4a, b showed that they are formed by the two phases of the tin amalgam, in contrast with previous studies, where the drops were characterized as rich in mercury [11] or described as formed almost entirely by mercury [4][5][6][7]. In summary, the darker and lighter zones in Figs.…”

“…5). Drops are present also on the top of some well pronounced craters, as previously detected [4][5][6][7][10][11][12]. SEM pictures in Fig.…”

“…The majority of studies on amalgam ancient mirrors were performed in the last decade and concerned the characterization of the tin-mercury amalgam layer, whose interface with glass constitutes the reflective surface of the mirror [1][2][3][4][5][6][7][8][9][10][11][12]. They indicated that this reflective layer contains about 25 wt% mercury and 75 wt% tin and that it consists of two different phases: a solid one, distributed as "islands", composed by about 20 wt% mercury and 80 wt% tin, surrounded by a liquid phase composed by about 95-100 wt% mercury and 0-5 wt% tin [1][2][3][4][5][6][7][8][9][10][11][12]. The amalgam alteration involves mercury evaporation and formation of tin monoxide (SnO, romarkite) and dioxide (SnO 2 , cassiterite).…”

“…Several studies among those cited above concern the alteration processes of the amalgam layer on the back side of ancient mirrors (interface amalgam-air) [1,[4][5][6][7][8][10][11][12], while a recent study was based for the first time on the investigation of the amalgam side in contact with the glass (reflective surface) [12]. It highlighted the formation of a superficial morphology of the amalgam alteration products in form of concentric rings, with two alternate different compositions.…”

Non-invasive analytical techniques applied to characterize the components of ancient golden medallions

“…This technique, which is usually performed on powders, is a micro-destructive technique because a small amount of the artwork is collected before performing the experiments. Non-destructive X-Ray diffraction (XRD) equipment was developed to study planar samples using techniques such as grazing incidence X-ray diffraction, which provides very precise information about the surface, atomic interface arrangement in the crystalline structure and composition of the depth profiles [16][17][18]. In addition, a recent study used Goebel crystal facilities to examine non-planar samples [19].…”