CHEMICAL ANALYSIS OF LATE ROMAN GLASS FROM QASR AL RABBAH, JORDAN

Abstract

Qasr al rabbah is an exceptional site that lies on the main Trajan road (the royal road) which pass

ing between Debaan and Karak, also provides unique evidence of the characteristics that illustrate

its importance in ancient time. X-ray fluorescence (XRF) on Roman glass was chosen as a reliable

technique to obtain and identify the raw materials, including the type of modifiers that were used

as well as the colorants and opacifiers used in Roman glass objects. Forteen glass samples have

been analyzed using XRF technique and statistical analysis both descriptive and multivariate. The

study revealed two groups of glass in the same region. The obtained results indicated the use of

Natron as fluxing agent with alkali contents as well as using the soda ash too as a second type.

Two compositional groups have been identified in this study, potash soda lime silicate K2O (Na2O)-CaO

SiO2 (K2O/Na2O>1), soda potash lime silicate Na2O (K2O)-CaO-SiO2 (K2O/Na2O<1) and potash silicate K2O-SiO2

glass systems, respectively. According to the visual inspection of the assemblage different corrosion

effects are noted. A few glass fragments show a significantly higher degree of corrosion. It is the

only sample in which a silver iridescent and a browning layer have been formed. Biocorrosion also

appear as an additional weathering factor. Moreover, the inner surfaces of the walls of some color

less sherds demonstrate high polymerization, which is not noted on the outside surfaces of the

same samples. The glass samples slightly tinted in yellow–green by the natural sand impurities,

was evidently and heavily corroded and gave indeed Na concentrations well below what was ex

pected from the known historical glassmaking.