LEAD-ALKALINE GLAZED EGYPTIAN FAIENCE: PRELIMINARY TECHNICAL INVESTIGATION OF PTOLEMAIC PERIOD FAIENCE VESSELS IN THE COLLECTION OF THE WALTERS ART GALLERY
4 4. CONCLUSIONS
The study of Ptolemaic faience vessels has yielded some exciting results. Analyses revealed that lead-alkali glaze was used on a chiefly quartz body in this particular group of Ptolemaic faience vessels, a composition very different from the alkali glaze typically used for pharaonic faience vessels. Although lead in glaze existed in earlier Egyptian faience (Vandiver 1983, specimens 183–115–774, 183–115–775, and 186–68–336), it occurred in isolated instances and was associated primarily with yellow colorant as a component of lead antimonate. In contrast, the lead appears to be used as a modification of glaze in the Ptolemaic period, when it may have been deliberately added to the alkali glaze to improve the glaze properties. Lead in a lead-alkali glaze can reduce the viscosity of the glaze during firing. It also enhances the optical brilliance of the glaze (Kingery and Vandiver 1986).
In addition, the results of this study suggest that Ptolemaic faience might have been the earliest known example of the use of lead-alkali glaze in antiquity. Lead (or lead oxide) had been used as a constituent in glass formulations for more than 3,000 years (Nordyke 1984). However, the first use of lead glaze in the West seems to have occurred during the Roman era, 100 b.c. to 100 a.d. (Tite et al. 1998). In the Near East, it was not used until about 200 b.c.; the Syrians and Babylonians first learned to use lead glaze for pottery (Rhodes 1973). A related group of glazes is known as tin-opacified glazes containing both lead and alkali. They were first produced in Iraq. A small amount of lead (1.0–2.6%) in alkaline glaze was first reported in early Islamic turquoise-glaze wares from Iraq, dated to about 700 a.d. (Mason and Tite 1997). There is no controversy about the dating of the Ptolemaic faience pieces at the Walters Art Gallery used for this study; the dates of their manufacture range from about 300 b.c. to 200 b.c. Their dates make them the earliest known examples of lead-alkali glaze reported so far.
Increased sophistication is evident not only in the development of the glaze but also in the manipulation of the glazes and the body. The bicolored surface was achieved by the application of two layers of glaze. Both the underglaze and the glaze were applied instead of self-glazed. The underglaze was applied overall first as a fine slurry mixture on the exterior, then was wiped away from the raised areas. The overall glaze was then applied on both the exterior and the interior. The body was made of finely ground quartz mixed with glaze material for good fusion. Copper and lead antimony were used in small amounts as colorants for green in the glaze. Cobalt (dominant), iron, and probably manganese in small amounts were used as colorants for blue in the underglaze. Lead antimonate was used as a colorant for yellow. The shape of the vessel and the relief surface were produced by the use of a mold, or piece molds, with additional enhancement through carving and/or incision.
Visually, changes took place in the aesthetic appearances of the Ptolemaic faience vessels as compared to earlier examples. Foreign motifs were incorporated in the design. A light green glaze color became fashionable instead of the previously predominant turquoise blue color. Relief designs were presented in contrasting glaze colors, instead of monochrome or separate inlay colors often seen in earlier faience vessels. Although fine and delicate faience vessels existed in the earlier periods, visual distinctions can be made when comparing the Ptolemaic vessels with the earlier ones. The molded low relief on the Ptolemaic faience vessels appears to be shallower than the low relief in the earlier faience vessels; the shapes of the Ptolemaic faience vessels are complex and somewhat exotic, such as the rhyton (see fig. 2).
The techniques of molding the quartz body, creating low relief designs, and the glaze application continued from the established tradition of Egyptian faience technology (Kaczmarczyk and Hedges 1983; Nicholson 1998). Yet, in other respects, Ptolemaic faience techniques incorporate change and innovation. The new developments may be the result of a natural progression built upon the traditional technology but may also come from influences outside Egypt. Little technical information is available about faience making in Egypt and elsewhere during the Ptolemaic period (Nicholson 1993, 39–41). In the case of the vessels studied, lead-alkaline glaze was deliberately used as an alternative to the predominant alkaline glaze. As faience technology progressed, the Egyptians themselves may have discovered the use of lead-alkaline glaze, either accidentally or by design; certainly, lead had previously been used for other purposes in Egyptian faience technology. Alternatively, the use of lead-alkaline glaze could have been linked to a transfer of technology from a neighboring culture beyond Egyptian borders. It is evident that foreign motifs and shapes were used in Ptolemaic faience production, revealing the mixture of cultures present in Egypt during that time. It is possible that this glaze modification was introduced by a foreign source and incorporated into Egyptian faience technology as an import.
This study is focused mainly on the interpretation of technical observations and scientific data from a particular group of Ptolemaic faience vessels. It paves the way for the understanding of how the Ptolemaic faience production fits into the history of Egyptain faience technology and for future study of this fascinating and technologically innovative method of faience production. More study is needed to place Ptolemaic faience production within a broader context, including trade occurring at the time as well as its relationships to the contemporary ceramics and glass industry in the surrounding regions. It is hoped that this study will serve as an impetus for such research.