Synergic analytical strategy to follow the technological evolution of Campanian medieval glazed pottery

Abstract

Three classes of medieval lead-tin-glazed ceramics (protomajolica, transition enamel pottery and white enamel pottery), from the archaeological site of Castello del Monte in Montella (Avellino, southern Italy), were investigated. Inductively coupled plasma-mass spectrometry (ICP-MS), optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy (OM and SEM-EDS) and X-ray powder diffraction (XRPD) were carried out on ceramic bodies, coatings and decorations in order to outline the technological features and define the nature of glazes and pigments. The aim of this work, in addition to delineating the features of production, is to confirm the archaeological hypothesis that transition enamel pottery produced between the fourteenth and fifteenth centuries, although having much in common with the protomajolica, is in fact a version of white enamel pottery, characterised by morphological and ornamental diversity. Our results show that both ceramic bodies and coatings feature different structural and compositional characteristics, linking the three ceramic classes and making it possible to confirm the archaeological hypothesis that transition enamel pottery can be defined as a ceramic class with transitional features between protomajolica and white enamel pottery.

Raman and SEM‐EDS insights into technological aspects of Medieval and Renaissance ceramics from Southern Italy

“…They are due to the dissolution and successive recrystallisation of SnO 2 in the melt and occur with typical dimensions ranging between less than 20 μm for white enamel group and up to 100 μm for protomajolica. [ 45 ] The ratio between the main SnO 2 band (635 cm −1 ) and Ip was calculated, and results are reported in Figure 5d, where the box plot shows how the grouping of the fragments in the already mentioned classes is confirmed. An increase in the mean and median of the (SnO 2 )/(Ip) ratio values is visible passing from protomajolica to enamelled pottery, in accordance with the higher content of cassiterite required to increase the coating opacity; “transition enamel” group exhibits intermediate values well separated from those of the “enamelled” one.…”

“…The SEM observations (Figure 4a) and EDS microanalyses (Figure 4b) revealed the presence of a thick layer at the interface rich in newly formed crystals of K and Pb feldspars, whose nucleation and growth are due to the reaction of the PbO with clay minerals from the ceramic body during firing; they are easily detected by SEM‐EDS [ 45,53–57 ] in literature. Up to now, no Raman spectrum was ever clearly and directly associated to these solid solutions; however, Kirmizi and co‐authors [ 36 ] studied late byzantine pottery and reported Raman spectra of feldpars comparable with those discussed in the present work, as well as SEM images of neo‐formed phases at the interface between the ceramic body and the glassy coating.…”

“…According to literature, the ratio between the area subtended by the cassiterite main peak and the glass Ip in the Raman spectra can efficiently be used to classify lustre potteries and faience (9th–14th centuries) samples. [ 36 ] Taking into account that one of the greatest differences highlighted in a previous work [ 45 ] between the three Montella ceramic classes can be observed in the SnO 2 /PbO ratio of the coating, the use of cassiterite Raman spectrum was considered as potential technological marker, distinguishing the three ceramic classes, especially the intermediate “transition enamel.” Raman spectra were acquired on the white portions of the 12 Montella samples (see, for example, Figure 5a–c) because fine dispersed particles of tin oxide have been observed in the studied samples. They are due to the dissolution and successive recrystallisation of SnO 2 in the melt and occur with typical dimensions ranging between less than 20 μm for white enamel group and up to 100 μm for protomajolica.…”

“…The findings from Montella belong to three classes of Medieval lead-tin-glazed ceramics: protomajolica (second half of the 13th century to the early 14th century), "transition enamel" products (14th-16th centuries) and white enamel with blue motives pottery (beginning of the 16th century) ( Table 1); the archaeological hypothesis states that these three classes resulted from the technological evolution in the field of glazed ceramic production, with "transition enamel" interpreted as an intermediate phase between the other two. [44,45] Findings from Ariano Irpino show a white enamel with blue motives and are attested starting from the beginning of the 15th century [44][45][46][47][48] (Table 1, Figure 1). Modica, [49][50][51] Scicli and Buscemi (South-Eastern Sicily) could all be considered at that time under the economical influence of the renowned ceramic production centre of Caltagirone.…”

A Possible Natural and Inexpensive Substitute for Lapis Lazuli in the Frederick II Era: The Finding of Haüyne in Blue Lead-Tin Glazed Pottery from Melfi Castle (Italy)

“…Normally, the high concentration and mobility of Pb in the coating of medieval/renaissance pottery, led to the neoformation of a Pb-rich corona around relict feldspars; in the corona, small euhedral and neomorphic Pb-rich crystals developed at the rim of the alkali feldspar in contact with the Pb-rich lead-tin glaze [ 27 , 33 ]. Similarly, in the M22 sample, the high mobility of some elements such as Si, K, and Pb allowed the formation of a K-rich corona around haüyne; in fact, the rim of haüyne, a silica-undersaturated mineral, reacted with Si and Pb, which are relatively more abundant in the lead-tin glaze, to form more silica-saturated crystals such as small neomorphic and euhedral Pb-rich-feldspar-like crystals, whose Raman spectrum was here highlighted and already found in [ 27 ].…”