Tag Archives: Merovingian dynasty

Conference Proceedings: Gemstones in the first Millennium

Researchers from different fields like archaeology, history, philology and natural sciences present their studies on ancient gemstones. Using precious minerals as an example, trade flows and craftsmanship, but also utilisation and perception are discussed in a cross-cultural and diachronic approach. The present volume aims at three main questions concerning gemstones in archaeological and historical contexts: »Mines and Trade«, »Gemstone Working« as well as »The Value and the Symbolic Meaning(s) of Gemstones«.

 

This volume contains the proceedings of the conference »Gemstones in the first Millennium AD« held in autumn 2015 in Mainz, Germany, within the scope of the BMBF-funded project »Weltweites Zellwerk – International Framework«.

You can preview the table of content and a preface here.

Technical Experiments 1: Producing a piece of silver foil

As an alternative to high karat gold foils fire-gilt silver foils have been used to produce the patterned Early Medieval backing foils. For my experiments, I needed a silver foil of a material thickness of 0,025 to 0,03 mm. My starting material was a sheet the size of 10×10 cm and a thickness of 1 mm. It was composed of 93,5% silver, 6,2% copper and 0,3% zinc. The authentic way to reduce the metal thickness would have been to draw down the material by forging. but to save time I decided to thin the sheet by rolling using a hand-operated rolling mill. The metal is worked in a cold state. It is primarily stretched in length. Because the process creates stresses in the crystal structure, the workpiece has to be annealed after several passes though the rolls: You have to heat it to a red state and then cool it down. Rolling the silver sheet to a material thickness of 0,03 mm would mean that its length expands up to 4 m! So repeated cutting off of smaller pieces was necessary. I started to roll the sheet immediately, reducing the distance between the rollers step by step, and I could go on until a material thickness of 0,1 mm was reached. Then the gap between the rollers couldn’t be made any smaller. So I continued sandwiching the silver between two copper sheets. During the whole rolling process the workpiece had been periodically annealed. The thinner the sheet became the greater was the danger of melting. Finally, I held two silver sheets, sizes 2,7×6,6 cm and 2,7×5,2 cm, of a material thickness of 0,03 mm in my hands, with some small stress cracks along the edges and both a little bit warped, probably because of an irregular roller pressure.

Fig.1: surface area melted during the annealing process, image field: 10,5×15,5 mm (photo: RGZM/Stempel)
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Fig. 2: stress cracks along the edge of the sheet, image field: 8×12,6 mm (photo: RGZM/Stempel)

 

Lit.: E. Brepohl, Theory and Practice of Goldsmithing, Brunswick 2001.

Archaeometric Investigation of garnet jewellery

Archaeological material from Hungary (late 6th- and 7th-century)

Deutsche Version | Team | Cooperations

Decorative use of garnet stones on fine metalwork has defined the goldsmith’s art in the Carpathian Basin for three centuries, although with varying intensity. After its main flourish between the early 5th and the middle the 6th century, its dominance was mainly limited to the material of some specific social groups. On the other hand, from the early 8th century, garnet inlay had completely disappeared from the design of fine metalwork. In the project we are focussing on one of the most interesting transitional periods, dated between the late 6th and the late 7th century, which in Hungary is called the Early and Middle Avar Periods. Continue reading Archaeometric Investigation of garnet jewellery