A WATER ABSORPTION ANALYSIS OF NABATEAN, NORTH AFRICAN AND OTHER CLAY LAMP FABRICS UNEARTHED AT THE RED SEA PORT OF ROMAN AILA (AQABA, JORDAN)

A water absorption analysis was conducted on 103 clay lamp samples to determine whether the fabrics of this pottery type are porous. If so, this would lend further support to the long-standing assumption that lamp makers coated their lighting vessels with slipnot just for decorative purposes, but as a means of preventing oil seepage of the fuel chamber. The samples were excavated at the Red Sea port of Roman Aila (modern Aqaba, Jordan) and belong to 10 different types originating from Arabia, Palestine, Egypt, Tunisia and Gaul. The results of the experiment reveal that clay lamp fabrics are porous, and comparatively more so than a reference group of non-lamp pottery from Pella (Jordan). Petrographic thin-section analysis of select fabrics confirms the presence of pores, cracks and propagating veins indicative of thermal stress resulting from repeated lamp use. Meandering veins identified in a nozzle fragment were created by the diffusion of vapours, probably originating from the burning lamp oil itself. Ancient lamp makers understood that, given its direct exposure to the extreme temperature of the flame, the nozzle was particularly vulnerable to breakage as a result of thermal shock. A porous lamp fabric, however, helped limit crack propagation, allowing the nozzle and the lamp body to expand and contract to avoid breakage.