Period: Iron Age (0 - 400 AD)

Project title: Legeringsforsøg med Campanske bronzeovne

Researchers: Archaeologists Mads Jylov, Mikkel B. Siebken, Casper S. Andersen og Martin Hamberg, University of Århus

Email: madsjylov(at)hotmail.com

Year: 2008

Research Problem:

In spite of bronze being an imported metal, bronze has been cast in Denmark since the Bronze Age. Bronze is a metal alloy of copper and tin, which is either too hard or too soft for robust tools. Whereas bronze has just the right combination of flexibility and sharpness, to be ideal for the tools, jewellery and weapons of prehistory. However there have never been found traces of bronzealloying in Scandinavia, to this day. Kilns for alloying bronze are known from antique Greek vase paintings, and are according to written sources from Roman and Medieval authors in use throughout prehistory. This is verified by archaeological finds of copper kilns from the Italian region of Campania. But were such kilns in use in prehistoric Denmark?

The alloying process, where tin and copper, at a temperature over 1000 °C, mixes to bronze, is difficult and hard work. Especially getting the temperature high enough is difficult. None the less the Roman author Elder Plini (23-79 AD), describes an alloying process in Campania, where only firewood is used for fuel. Theoretically it should be impossible to achieve high enough temperatures without charcoal, but perhaps Plinis technique has unknown potential?

Researchers Conclusion:

Based on Plinis description of alloying methods, using wood as fuel, a team of researchers from the University of Århus tried to recreate the process in order to determine, whether the process was possible, asses the quality of the bronze produced and identify recognisable waste and debris from the process. Two identical experiments were carried out, which revealed the possibilities of the process. The experiments very clearly showed that it was possible to complete the alloying process using only wood as fuel. The kiln constructed for the experiments was very effective and the process was easy to control. The Bronze proved to be of varying quality, but the alloy was generally best the longer the bronze had stayed in the oven.

Then the kiln was dismantled and registered according to ordinary practice. The different kinds of waste products were collected and analysed. The experiment produced a variety of waste, quite similar to archaeological traces created by crucible casting, but also contained waste with very different characteristics.

With its combination of classical sources and experimental archaeology, this experiment has given a series of insights into what might have been a prehistoric alloying process and its waste products, enabling future identification of finds of prehistoric alloy kilns.

Status:

The experiment will continue in 2009.

Reference number HAF 14/08