Förlorat järn

Sammanfattning: Lost Iron – requirement and consumption of iron and steel in agriculture in medieval Sweden This study aims at an estimation of the amount of iron required for agriculture during the Middle Ages in Sweden. To calculate this we need to know which implements were used, their weights and how they were subjected to wear. Research on wear has been very scarce but it is of great importance to measure how much iron that was needed to replace what was taken away by constant wear, i.e. on shares for ploughs and ards. To achieve this a new method was devised. The method is based on previous research by Grith Lerche, with additional analyses and calculations. The method presented and used is called Wear Calculation Method and consists of five steps. Step 1: Study of medieval agricultural implements, their shape and weight. Step 2: Metallurgical analysis of selected implements, to answer questions about materials and how they were processed. Step 3: Experimental Archaeology: Manufacture of replicas of the implements analyzed in step 2. Step 4: Experimental Archaeology: ard ploughing and haymaking with replicas of ard shares and scythes for the purpose of measuring wear. Step 5: Analysis of the wear experiment, results and calculations of consumption of iron and steel in medieval agriculture. The experimental part of the thesis focuses on ard shares and scythes, since the ard and the scythe were the main implements for ploughing and haymaking during the Middle Ages in Sweden. These experiments were carried out during two seasons at Östra Järvafältet, north of Stockholm, Sweden. I have measured wear on the ard shares in grams per kilometer. But more relevant and often more compatible with data from written sources is a measure of how many grams that are worn off per hectare or any other given unit of land. The wear is approximated at 100 grams of iron and steel per ploughed hectare (10 000 m2), in conditions similar to the situation when the replicas were used. I chose to do my analyses on two different spatial levels, the farm and the county. The results prove that ard ploughing means much heavier wear on the implements compared to haymaking. Generally you needed an annual addition of slightly over 1 kg of iron to plough the fields of a normal-sized farm in Uppland. Thus we may estimate the total amount of iron required in Uppland to replace the wear caused by ploughing to 8,4 ton a year. These results show that iron and steel production were of great importance for the High Medieval economic expansion and modernization, where increased iron production and consumption as well as simultaneous expansion of arable land were vital. Between the end of the first millennium and the mid-14th century, the population of Sweden approximately doubled in size, much like the rest of Europe. Iron was a most important third factor (in combination with an increased population and the cultivation of new land) in this expanding age, ca AD 1000–1300. Production and consumption of iron and steel increased sharply during this period and it reached every person, farm, meadow and field in the country. This is a sure sign of a very developed market and system for the distribution of iron and steel.