 talk about energy expenditure calculations of Bronx-Age metalworking technology and this talks based on my master thesis which was submitted to the University in 2016 and will be published in the German series Archäologische Berichte. So in central European Bronx-Age a major transformation process in metalworking technology is evident and I will show that the observed changes are also visible in the energy expenditure invested in Bronx-Age metallurgy. At first I would like to explain some basic concepts of my work. The energy expenditure characterizes the expenditure used by an activity for example the building of a house. It is measured in person hours. One person hour corresponds to the work one person can provide in one hour and it is also referred to as expenditure of time, amount of work, effort, labor cost or labor input. The next terms I like to discuss are labor and value. My work is based on the assumption that the invested labor reflects the so-called natural price within classical economics which results from the sum of expenses used for the production and distribution. Karl Marx describes a similar concept which he calls exchange value. So when I talk about the calculation of energy expenditure these are the underlying concepts. A totally different question is whether in prehistory the value of object is also expressed and the labor invested for their production. This cannot be answered using archaeological methods. My working area encompasses central and southern Germany as well as parts of the Austrian Swiss and Italian alps where archaeological evidence for primary and secondary metallurgy exists. My working period is the central European Bronx age between 2200 and 800 BC. On the map selected mining sites are indicated which will be considered later in my talk. So the following remarks refer to the working area only unless dated otherwise. Before I get to the energy expenditure calculations I briefly would like to summarize the production steps of Bronx age metallurgy because this is important for further understanding. My energy expenditure calculations include only those parts of the production sequence with direct archaeological evidence. These are mining activities or identification, smelting, alloying, casting and post-processing. Looking at the archaeological evidence for Bronx age metallurgy some differences between the early Bronx age and contrast to the middle and late Bronx age can be observed around 1800 BC mainly in the smelting and alloying process. This is important because it is greatly reflected in the energy expenditure and demand for wood. I presume in my calculation that during the early Bronx age copper was produced in herds pits using oxidizing smelting techniques as indicated by features from the Trentino and in the middle and late Bronx age smelting facilities with shaft furnaces and roasting beds using reducing techniques as indicated by features from the eastern Alps. The alloying process changes at the end of the early Bronx age when copper and azainic copper are replaced by tin Bronx. Next I would like to explain how I conducted my calculations and as the basis for my work I studied the archaeological evidence in the working area to reconstruct the production steps of the metalworking process which I just showed you. And so how do we calculate the energy expenditure for a 4,000 year old process for which no written record exists? I did it with the help of experimental archaeology and for this I collected information about the energy expenditure from about 80 scientific publications of archaeological experiments. I collected the time data and the weight of the used resources ore and copper and wood in kilograms to make the data from different experiments comparable. The time data were put into relation with the weight of the required resources. This means so and so much kilograms wood is required to smell so and so much kilograms copper ore. In addition a copper slash ore wood ratio for every production step or technique was used in mind. For example one to two or one to one ratio. This makes it possible to calculate the demand for wood from the ratio copper ore to wood and charcoal findings from different sites indicate that wood and not charcoal was used in most production steps. In this manner it is possible to calculate the energy expenditure and demand for wood for each production step. At this point I decided to implement the ore wood ratio of the different production steps into a Microsoft Excel sheet to speed up the calculation process and to enable the testing by means of examples. I used the weight of the artifacts as an indicator for the required amount of raw material and in this manner I am able to calculate the energy expenditure and demand for wood for any copper or bronze object whose weight is documented. Thus it is likewise possible to calculate the energy expenditure and demand for wood for artifacts from one specific context for example for a horde inventory and it is also possible to use the estimations of copper output from different mining sites to calculate the demand for wood for the artifacts from specific mining sites what I will explain in detail in a moment. On this side you see the main results of my calculations for bronze age metallurgy in a diacronic perspective. I used the production of 100 ads as an example with the artifact category was chosen that was available throughout the bronze age in different types and 200 grams was chosen as an average weight for the artifact category. The energy expenditure is given in person hours short pH and the demand for wood is given in kilograms and in cases where the demand for wood is not specified no information was available. So to conclude as you can see here the production of 100 copper ads is using early bronze age production techniques needs about 4600 hours or 46 hours for one copper ads in the early bronze age. The production of 100 tin bronze ads is using middle and late bronze age technology needs about 3600 person hours or 36 person hours for one tin bronze ad in the middle and late bronze age and this difference can mainly be ascribed to the less effective oxidizing smelting process used in the early bronze age which is indicated here. The energy expenditure for the production of tin is assumed to be one tenth of the expenditure for copper assuming the tin bronze is contained 10% of sim which you can see here. Wood is required as a fuel mainly for the mining activities the smelting process casting and post-processing. The demand for wood is calculated from the war wood ratio as I explained on the former slide. The results show that in the early bronze age production process that the early bronze age production process needs about 116 kilograms of wood to produce one copper ads. While the middle or late bronze age production process needs only 90 kilograms of wood to produce one tin bronze ads. This indicates that the later process is more effective in terms of research resource consumption because the reducing smelting process has a lower demand for wood. Hence with the end of the early bronze age at around 1600 BC we can see a transformation in metalworking technology which is reflected in the energy expenditure and the demand for wood. As mentioned earlier it is possible to use the estimations of copper output from different mining sites. Therefore I have selected some mining sites for which estimations of the copper output were available because only few estimations of copper output are available from the working area. Sites from neighboring European regions were also included. This chronological scheme shows the dating of the selected mining sites. The sites concerned here are Saint-Vervon and Bronze, Mount Gabriel and Ireland, the Mittaberg region in Austria and Iwona and Bulgaria. Most of them fall into the time frame of the central European bronze age with the exception of Iwona. On this slide you see a graphic representation of my approach and an example below. The example used here is the Mittaberg main load in Austria. So this site is dated to the period 1600 to 900 BC. It has therefore a period of use of 700 years. According to Eibner the total copper output from the Mittaberg main load was 10,000 tons. The average copper output per year would therefore be 14 tons. If we assume that one artifact has a weight of 200 grams this would result in 70,000 artifacts, possibly produced per year. So the demand for wood for the production of these artifacts calculated from the ore wood ratio would thereby be around 7,000 tons per year. Let's have a closer look on the number of potentially produced artifacts and their demand for wood. This diagram shows the number of artifacts which could have been produced from the copper of the selected mining sites in one year. Although no clear chronological lines can be drawn there's a tendency to say that the earlier sites used here as a comparison produce less copper and therefore artifacts than the Mittaberg main load. With Saint-Garonne for example producing 17,500 artifacts per year and the Mittaberg main load producing copper for 17,000 artifacts per year. And the demand for wood similar tendencies can be observed. The demand grows with the number of produced artifacts. We can see the production of the artifacts. We can see that the production of the artifacts from Saint-Garonne requires about 2,000 tons of wood. While the production of the artifacts from the Mittaberg main load requires about 7,000 tons of wood per year. To conclude I was able to show you that around 1600 AC transformation in metalworking technology is visible which is reflected in the energy expenditure and the demand for wood. I showed that it's possible to compare the energy expenditure for different production steps of bronze age metallurgy. The required energy expenditure and demand for wood decreases with the change in smelting technology at around 1,600 BC. This means that the production process gets more effective and allows for the production of larger amounts of metals with a lower investment of resources. In turn we know from the archaeological record that from the beginning of the middle bronze age onwards the mining activities and the copper output increased significantly in the working area. This resulted in an increasing total energy expenditure and demand for wood in the middle and then bronze age. All together the name factors point towards the major transformation in bronze age metalworking technology at the end of the early bronze age around 1,600 BC.