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

Abstract

An analytical investigation performed on Southern Italy pottery highlighted the usefulness of Raman spectroscopy to give answers to archaeological questions. It can provide important information concerning the production technology and raw materials constituting the glassy coatings. Raman spectroscopy was supported by Scanning Electron Microscopy coupled with Energy Dispersive X‐ray Spectroscopy (SEM‐EDS) for observations and elemental analysis. The studied samples, ranging from the 13th century lead‐tin‐glazed protomajolica to the 15th –16th enamelled pottery, come from the Castles of Montella and Ariano Irpino (Campania), from the castles of Scicli and Modica and from surveys carried out in Buscemi and Caltagirone (Sicily). Glassy matrices, opacifying agents, colour‐related raw materials and body‐coating interface crystalline phases were investigated. Though the coatings resulted all typically lead‐rich glass types, lumps showing a different Raman profile suggested that at least in one case, the batch was adultered with recycled glass waste. Furthermore, samples coming from Montella, belonging to the three main classes of ceramics defined by archaeological hypothesis, could be grouped according to their cassiterite content. The crystallization of lead–potassium feldspars at the coating‐body interface in a group of samples was ascertained. With regard to the origin of colours, the spectra of blue coatings highlighted phases that can be traced back to the use of Co‐based and Co–As‐based raw materials, while turquoise decorations were found to contain malayaite.

Cobalt and Associated Impurities in Blue (and Green) Glass, Glaze and Enamel: Relationships between Raw Materials, Processing, Composition, Phases and International Trade

“…It is important to note that as early as the Ptolemaic and Roman periods, lapis lazuli was also used as a colouring agent of the glaze and enamels on glass [69][70][71][72][73][74][75]87,88], a fact still today ignored by most scholars. Taking into account that cobalt appears to have been used to colour glass continuously since the late Egyptian/Mesopotamian Antiquity [89][90][91][92][93][94][95][96][97], we should ask why the coloration of glazes with cobalt almost disappeared after the Ptolemaic period up to the Tang Dynasty (8th-Century) in China (at the kilns of Baihe and Huangye, close to Gongyi, in Gongxian, Henan province [98][99][100][101][102][103][104]) and the Umayyad Caliphate (661-750 CE) in Mesopotamia [19]. One reason can be found in the continuous recycling of blue glass proved by many shipwrecks in the Roman [105,106] and to some extent during the medieval period [14,106].…”

“…Enamelled glass artefacts were objects produced for the elite in society. Photographic documentation on Islamic [65][66][67][71][72][73][240][241][242] and European [96,[243][244][245][246][247][248][249] enamelled glass is available but the number of specific scientific analyses of the enamels on glass is much smaller than those on pottery. Lead-rich compositions were generally used for this type of enamelling to facilitate the melting at relatively low temperatures [242,[250][251][252], which are lower than that of the body.…”

The Irreplaceable Contribution of Cross Sections Investigation: Painted Plasters from the Sphinx Room (Domus Aurea, Rome)

“…The Raman spectra acquired on these grains all show similar features: Spectrum BR (Figure 8) is the average of 3 points. The broad bands at 350, 497, and 637-717 cm −1 can support the identification of maghemite γFe 2 O 3 [36][37][38][39]. Maghemite is a yellowish brown compound, which has been reported to form by heating of lepidocrocite γFeO(OH) [37].…”

Portuguese 16th to Early 18th Century tin Glazed Ceramics Found at the Tagus Estuary Saltpans

“…The bending band of SiO 2 (δ Si-O ) exhibits a maximum at 462 cm -1 and the stretching band (υ Si-O ) at 996 cm -1 . Clearly this latter value indicates a lead based glaze [25,26]. The ratio of the bending band area relative to the stretching band is about 0.5, pointing to a relatively low temperature of the kiln, about 800 ºC [25].…”