ABSTRACT
Japanese craftspeople have dominated the art of patinating copper-alloys since the 15th century, using precise alloy compositions and complicated patination processes in different hot solutions to create a variety of colours on swords fittings such as tsuba. While this complex tradition is increasingly popular in the East, the reasons behind the choices made by craftspeople in the selection of the components of the alloys and are still not fully understood. This paper investigates the effect of different alloying elements (tin, gold, and silver) on the resulting patina. Experimental results are compared with optical and compositional analyses on historical Japanese artefacts, confirming the effects of the different alloying elements on the patina characteristics and colour. The absence of tin and the presence of gold limit the growth of an oxide layer and promote the formation of a thin patina characterised by a smooth appearance without visible grains. Therefore, a limited thickness of the patinas is a key aspect for the production of the desired colour and appearance of the patinas. The first colorimetric analysis on historical Japanese artefacts demonstrates the influence of gold, silver and tin in the final patina colour, validating the observations in the experimental replicas.
ABSTRACT
Archaeological glass contains information about the movement of goods and ancient economies, yet our understanding of critical aspects of the ancient glass industry is fragmentary. During Roman times, distinct glass types produced in coastal regions of Egypt and the Levant used evaporitic soda (natron) mixed with Nile-derived sands. In the Levant, furnaces for producing colourless Roman glass by addition of manganese have been uncovered, whereas the source of the desirable antimony-decolourised Roman glass remains an enigma. In the Edict of Diocletian, this colourless glass is listed as "Alexandrian" referring to Egypt, but its origin has been ambiguous. Previous studies have found overlapping strontium and neodymium isotope ratios for Levantine and Egyptian glass. Here, we confirm these findings and show for the first time, based on glasses from the ancient city of Gerasa, that hafnium (Hf) isotopes are different in Egyptian and Levantine natron glasses, and that Sb Roman glass is Egyptian. Our work illustrates the value of Hf isotopes in provenancing archaeological glass. We attribute the striking difference in Hf isotopes of Egyptian versus Levantine glasses to sorting of zircons in Nile sediments during longshore drift and aeolian transport along the south-eastern Mediterranean coast leaving behind a less juvenile fraction.
ABSTRACT
136 glasses from the ninth-century monastery of San Vincenzo and its workshops have been analysed by electron microprobe in order to situate the assemblage within the first millennium CE glass making tradition. The majority of the glass compositions can be paralleled by Roman glass from the first to third centuries, with very few samples consistent with later compositional groups. Colours for trailed decoration on vessels, for vessel bodies and for sheet glass for windows were largely produced by melting the glass tesserae from old Roman mosaics. Some weakly-coloured transparent glass was obtained by re-melting Roman window glass, while some was produced by melting and mixing of tesserae, excluding the strongly coloured cobalt blues. Our data suggest that to feed the needs of the glass workshop, the bulk of the glass was removed as tesserae and windows from a large Roman building. This is consistent with a historical account according to which the granite columns of the monastic church were spolia from a Roman temple in the region. The purported shortage of natron from Egypt does not appear to explain the dependency of San Vincenzo on old Roman glass. Rather, the absence of contemporary primary glass may reflect the downturn in long-distance trade in the later first millennium C.E., and the role of patronage in the "ritual economy" founded upon donations and gift-giving of the time.
