Production Technology of Roman Lead‐glazed Pottery and Its Continuance Into Late Antiquity

Abstract

A broad selection of Roman lead‐glazed pottery dating from the first century ad through the fifth century ad was studied to establish locations of workshops and to address their technology of production. The ceramic bodies were analysed by ICP–AES. In addition, lead isotope analysis was undertaken on a selection of glazes. These findings suggested that there were several regions responsible for the production of lead‐glazed ceramics in the western Roman world, including central Gaul, Italy and, probably, Serbia and Romania. Using the body compositions as a starting point, the glazing techniques employed by each of the potential workshops were examined using electron probe microanalysis. It was determined that there were two primary methods of glazing. The first method used lead oxide by itself applied to non‐calcareous clay bodies, and the second method used a lead oxide‐plus‐quartz mixture applied to calcareous clay bodies. Based on these data for clay composition and glazing method, transfer of technology from the Hellenistic east to the western Roman world was proposed. Likewise, the inheritance of lead‐glazing technology into late antiquity was established by making comparisons to lead‐glazed ceramics dating to the seventh to ninth centuries from Italy, the Byzantine world and Tang Dynasty China.

The Medieval lead-glazed pottery from Nogara (north-east Italy): a multi-methodological study

“…This composition matches ranges of non-calcareous, low-alumina clay, normally used in Italy for lead-glazed pottery production of late Roman and early Medieval age (Paroli et al, 2003;Walton and Tite, 2010). As regards the firing technology, although the iron content is very similar in all samples, the division between Fe 2þ and Fe 3þ , and therefore the reduction index (RI), expressed by the FeO/FeO tot ratio (Maggetti and Galetti, 1981), is very variable ( Table 2).…”

“…The euhedral habitus of the crystals and their small size (<5 mm) in all the Nogara samples suggest comparable firing conditions, probably between 750 C and 850 C (Molera et al, 2001;Walton and Tite, 2010) with short heating time. The relatively low temperature of firing was still sufficient to allow the growth of a great number of crystallites; however, firing time and temperatures were too low to allow the crystallites to exceed the size of …”

“…Therefore, subtracting the lead oxide content from the glaze composition and recasting the obtained data to 100%, the resulting composition should be close to that of the ceramic body. In addition, contents of other elements of glaze should remain constant throughout its thickness (De Benedetto et al, 2004) for firing time of at least one hour (Walton and Tite, 2010). In contrast, when a leadesilica mixture is used, the lead and silica react during firing to form the glaze, into which there will be some subsequent diffusion of body components (e.g., aluminium, calcium, iron, alkalis).…”

“…In attempting to establish the production technology of lead glazes, interactions between the glaze mixture and the clay body should be considered (Tite et al, 1998;Walton and Tite, 2010). As discussed by Hurst and Freestone (1996), when a lead compound (oxide, sulphide or carbonate) is used by itself, the lead diffuses into the body during firing, reacting with it to form a glaze.…”

Revisiting the beginnings of tin-opacified Islamic glazes

“…However, rather than being the result of direct contact with Byzantine glassmakers, the employment of lead stannate is more likely to have been as a result of contact with Syrian and Egyptian glassmakers who continued to work in the Byzantine tradition whilst now operating under Islamic rule. The use of high lead glazes for these ceramics can similarly be explained in terms of the Egyptian and Syrian potters continuing the Roman, and subsequent Byzantine, use of high lead glazes (Waksman et al, 2007(Waksman et al, , 2008Walton and Tite, 2010). Further, the use of yellow lead stannate opacified glazes of very similar composition in Samarra, Kish and Susa establishes that, together with the proposed stylistic transfer eastwards from the Mediterranean to Mesopotamia, there was an equivalent technological transfer.…”