By the hand of the smelter: tracing the impact of decision-making in bloomery iron smelting

Slag analyses from archaeological iron smelting sites are common. Rigorous analyses of iron and slag from successful experimental smelting, however, are still rare. Furthermore, thorough analyses from a series of smelts, and of the slag produced in different phases of the smelt, are exceedingly rare. The present study investigates the effect of an iron smelter’s decision-making and skills on the products of the smelting process: iron and slag. Four smelting experiments were carried out in a shaft furnace with slag tapping using iron ores from the Southern Levant. Using various analytical techniques, including portable X-ray fluorescence, optical and electron microscopy, metallography, and hardness tests enabled us to correlate the properties of the final products with adjustment of various parameters during the smelting process. The latter include airflow and charging rate, temperature, residence time in the reducing zone, ore-charcoal ratio, and control of the slag characteristics. Results obtained allowed us to empirically demonstrate the direct impact of decisions made by the smelter during the complex technological practice of bloomery smelting. Analysis also highlights the benefits of moderately reducing conditions controlled by the smelter to produce good-quality, low-carbon iron, which is particularly relevant within the geological setting of the Southern Levant.