Iron : aspects of the industry during the Iron Age and Romano-British periods
Our knowledge of the earliest methods of iron production owes a great debt to 19th_century accounts of the bloomery technique as still practised in parts of Africa and Asia. Inevitably, and in common with other aspects of archaeology, many prejudices of that period have been perpetuated up to the present day in the literature. Additional bias has resulted from the influence of modern metallurgy. An attempt has been made to identify and correct these misconceptions in the light of new archaeological evidence in conjunction with recent smelting experiments. To enable a clearer understanding and interpretation of archaeological field remains, the bloomery process is fully explained in relation to furnace structures, ores and products, and the reduction process is illustrated with appropriate microstructures of the products. Roasting and smelting experiments have been used to test the viability of iron sulphide ores as ancient sources of iron. These iron pyrites and marcasite nodules are common over large parts of southern England. Sideritic and limonitic ores were also smelted. The experimental products, slags and iron, were analysed to assess the relationship between ores and slags, and the results tabulated. The relationship between the microstructure of the iron and slags and furnace conditions was also evaluated. The main analytical techniques employed were metallography, electron probe microanalyser (EPMA), X-ray fluorescent spectrometry (XRF), scanning electron microscopy (SEM), and inductively coupled plasma emission spectrometry (ICP). Microstructures of both slags and iron are presented together with backscattered electron images and X-ray element maps. Furnace typologies relating to iron production in both Britain and the Continent are critically evaluated, and an overview of the industry during these periods is presented. The corrosion of slags and its implications for the analysis of archaeological specimens are considered.