Analytical study of a Roman bronze steelyard balance from Leptis Magna, Libya: manufacturing techniques and burial degradation

Abstract This study presents a comprehensive investigation of a Roman bronze steelyard balance excavated from Leptis Magna, a UNESCO World Heritage Site and prominent commercial center in Roman-era northwestern Libya. Our aim is to reconstruct the instrument’s manufacturing techniques, diagnose burial-driven corrosion mechanisms alongside component-level alloy heterogeneity, and translate these findings into conservation guidance. Integrated analytical methodologies—including optical microscopy, metallography, X-ray diffraction (XRD), Scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), and portable X-ray fluorescence (XRF) spectroscopy—were employed to characterize the artifact’s material composition, manufacturing techniques, and degradation patterns. The analyses reveal a composite construction employing both copper and leaded tin bronze (Cu-Sn-Pb) components. The main structural fittings were fabricated from bronze using combined casting and hammering techniques, while specialized parts such as suspension chains were constructed from twisted copper foils wrapped around an organic core. While key functional fittings (e.g., counterweight, graduated scale) are missing due to corrosion during burial, preserved components—including the weighing pan, main beam, suspension rings, and mounting brackets—retain partial metallic cores amidst widespread mineralization. Corrosion products identified include cuprite, and chloride-based phases (atacamite and cotunnite), indicative of prolonged burial in chloride-rich soils. These results shed light on the economic and technological aspects of Roman-era trade instruments while emphasizing the importance of preserving such artifacts for historical and cultural understanding.