Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Medieval glazed ceramic from Caesar's Forum (Rome, Italy): Production technology Caterina De Vito a, ⁎ , Laura Medeghini a , Sonia Garruto a , Fulvio Coletti b , Ilaria De Luca b , Silvano Mignardi a a Department of Earth Sciences, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy b Soprintendenza Speciale per il Colosseo, il Museo Nazionale Romano e l’Area Archeologica di Roma, P.zza dei Cinquecento 67, 00185 Rome, Italy ARTICLE INFO Keywords: Caesar's Forum Medieval Roman heavy lead-glazed ceramics OM-XRPD-SEM-EMPA Technological background ABSTRACT This study is focused on Medieval Roman heavy lead-glazed ceramics from the archaeological site of the Caesar's Forum (Rome, Italy), dated from the 10th and not beyond the first decades of the 11th century. Optical mi- croscopy (OM), X-ray powder diffraction (XRPD), scanning electron microscopy (SEM-EDS) and electron mi- croprobe analysis (EMPA) have been used for the archaeometric characterization of the ceramics. Petrographic analysis of the body indicated the occurrence of three petro-fabrics, mainly composed by abundant quartz, feldspars, nodules of iron oxides, rare fragments of siliceous rocks, very rare fragments of calcareous rocks, pyroxene, biotite and olivine. This mineralogical assemblage suggests that the ceramics were fired in the range 950–1050 °C, under oxidizing conditions. SEM and EMP analysis show that the ceramic body was produced with non-or moderately calcareous clays and the heavy glaze with lead oxide, silica, alumina and alkalis. The mi- crostructure of the glaze and the relationship with the body suggest that for the production of the ceramic repertoire of the Caesar's Forum either the single or the double firing techniques were used. 1. Introduction Technological production studies of archaeological ceramics re- present one of the most popular subjects in the field of archaeometry [1,2]. In the last decades, several mineralogical-petrographic and che- mical techniques have been involved in the study of ceramic material with the aim of understanding fabric variability and firing conditions for assessing the nature of raw materials as well as provenance [3–8]. The ease of finding the raw materials and the relative simplicity of the ceramic preparation favored the widespread production of such artifacts, becoming in the millennia a memorable archive of testi- monies, which are useful to reconstruct the technological background of ancient populations. The use of heavy glazes, coating earthenware ceramic, has been produced in the ancient Egypt and Mesopotamia areas since the 1500 BCE [9–11]. Commonly, a “frit” (crushed glass) of alkalis and silica was directly applied on the ceramic surfaces to form glazes. Hedges and Moorey [12] and Hedges [13] analyzed a huge set of glazed ceramic fragments from Kish and Niniveh (Iraq) dated between 1300 BCE and 550 CE using optical emission spectroscopy (OES) and X-ray fluores- cence analysis (XRF). They proved that the composition of the glazes was mainly alkali-lime-silica, similar to Mesopotamian glasses [14]. In Hellenistic and Roman ages the use of lead compounds in the production of glazed coating became common [15] due to the possi- bility to reduce the cracks connected to their minor thermal expansion coefficient and a major optical brilliance similar to metals. The high- lead glaze appeared in Anatolia during the 1st century BC and spread throughout the Roman world between the 1st century BC and the 1st century AD [16,17]. It was characterized by high amounts of Pb content (45–60% PbO), an alkali content less than 2% and an alumina content (Al 2 O 3 ) between 2% and 7% [9]. Walton and Tite [17] indicated Gallia, Italy, Serbia and Romania as the main production centers of Pb glazed pottery during Roman Empire. These authors described two methods of glazed coating production: the first using Pb oxides applied on non-calcareous body pottery, the second one consisting in the use of Pb oxides, silica, alumina and alkali applied on calcareous ceramic body. Later (8–9th century AD), tin compounds were added in the pro- duction of the glazed coating in the Iraq centers [18], probably to imitate Chinese white ware. Chemical studies by scanning electron microscopy (SEM-EDS/WDS) of glazed ceramic fragments from Sa- marra, Nippur and Hira in Iraq; Susa and Siraf in Iran; Fustat in Egypt and in Bahrain proved that the first tin opaque glazes were produced and used in Iraq [18]. https://doi.org/10.1016/j.ceramint.2017.12.104 Received 20 October 2017; Received in revised form 13 December 2017; Accepted 14 December 2017 ⁎ Corresponding author. E-mail address: caterina.devito@uniroma1.it (C. De Vito). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2017 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: De Vito, C., Ceramics International (2017), https://doi.org/10.1016/j.ceramint.2017.12.104