 Dear colleagues, the Plano Convex ingot is the most common ingot type of for copper and their alloys in late Bronze Age in Central Europe. In the following presentation, I will speak about their production and partition as well as their possible practical use in barter ore trade. At the beginning, I must bore you a little bit with terminology. In the English-speaking world, this ingot type, characterized by a flat topside and a bulged underside, is known as Plano Convex ingot. I will use today the acronym PCI for it. In Austria, Germany, and also here in Switzerland, the traditional name is Gusskuchen. The direct translation into English will be Casting Cake, a term which is also very appropriate because it describes the production process, as you see later very well. Smelted copper with Plano Convex shape has been known since early metallurgic times. First examples we know from copper age, like this piece from the Handlover Hort in Slovakia. In the course of the Bronze Age, the PCI is evidenced throughout Europe and the Mediterranean especially in horts and as cargo material from shipwrecks. This form was additionally used in larger number in Persian Gulf area and in settlements in the Indus Valley. In Iron Age, we find PCIs in Europe and also in Asia. Also the Romans cast the copper in similar form, as documented by ancient copper ingots found in Wales or along the southern shore of France. Especially from the late medieval to early modern periods, the PCI celebrates a comeback. As you can see on ingots from shipwrecks from the west and east coast of Africa, within Europe produced ingots by the trading house of Fugge in Augsburg, Germany. Why shows this ingot form for copper such a wide chronological and geographical range and why is it so common in late Bronze Age? The answer should be in the simple production of ingot and mold as well as the circumstance that the PCI is also very suitable for transporting and further processing. There are different views on how the PCI was made. According to some publications in Austria and Hungary, the PCIs are the primary product of copper extraction formed during smelting on the base of the furnace. But this formation process is in contradiction with features on the most of the PCIs as you will see in a moment. For me it's more likely that the end product of the ancient smelting process were amorphous copper lumps mixed with slag which needed to be melted and recast. Therefore, the PCI is rather the product of a secondary process in which the molten metal is cast into a shallow pit in the ground or in a bowl shaped mold. Rather the pore was carried out by use of crucibles or by discharging molten metal from the bottom of the furnace into a forehead or a tapping pit is still open. The fact that the majority of the PCIs were actually cast is indicated for example by flow structures at the top surface. That the PCIs were not poured in a single casting event but in several casting batches show the multi-layer structure of many PCIs. Depending on how much time has elapsed between the batches the result is the complete fusion of the metal layers or the formation of internal cooling rims between them. The rims can be described as sharp cracks or blurred gas bubble horizons among the layers. The primary form and dimensions of the PCI results of many factors like the shape, slope and size of the casting mold, the material of the mold and the conditions during cooling. The diameter mostly varies between 8 and 30 centimeters while the thickness ranges frequently between 1 and 10 centimeters. Some pieces even reach diameters over 45 centimeters. The weight of complete examples is an average between half and eight kilograms but examples up to nearly 15 kilograms are known. Very important to observe is the fact that the relation between diameter, thickness and weight at the PCIs is not linear and can fluctuate. The reason lies in their high porosity caused by gas evolution and shrinkage that forms numerous pores and cavities inside as well blisters on the surface during solidification. Sometimes the porosity reach 15 to 40 percent of the volume at the PCI. Liquid cover has the tendency to absorb gaseous gases from the environment. So the thereby from a combustion reaction between the liquid cover and the mold material from the burning charcoal, from moisture in the mold or from the humid air. These gases are dissolved in the melt and are released while cooling as gas bubbles which aspire to the top surface of the ingot. They show different forms from spherical bulges, overburst blisters to more or less deep bubble craters. Complete PCIs usually have a round shape but there are also more elongated pieces with a void, sub rectangular or drop shape. PCIs are typically flat along the top and covered on convex on the base. The cross section of the PCIs are diverse and show variable profiles consisting of different combinations of the flat concave or convex top and bottom sides. The PCI can also reach extreme manifestations. On the one hand almost hemispherical and bell shaped examples exist and on the other hand there are very flat pieces which look like slabs. The degree of fragmentation of the PCIs in late Bronze Age Horts is typically very high. So only a few intact specimens are contrasted with a large number of broken pieces as you can see here. This is the result of a dark edging, dark edging, breaking when they were traded, processed, hoarded or sacrificed. Pure copper is very ductile and therefore hard to break on the cold conditions. So most of the PCIs are break in a red hot state immediately after casting or after a later heating in a charcoal fire. A high porosity was beneficial for breaking the ingots into fragments because the fractures could spread along the pores and cavities through the copper matrix. Other factors that facilitate the partition but cannot explain here in detail are the chemical composition especially a higher content of elements such as a scenic or iron as well as microscopic impurities along the crystal or grain boundaries like cobrite or copper sulfide inclusions. These factors can dramatically deteriorate the mechanical properties of the copper and make it brittle. Principally the PCI shows various deformations and tool marks that suggest the use of different hammers, hatches and chisels during the dividing process. Often the PCI shows scratches or deeper notches that were accurate in a dewy copper on the top surface to determine where to divide it into halves and quarters. The further procedure was depending on the porosity and thickness of the PCI. If an ingot was rich in gas bubbles and copper or copper sulfide inclusions it could be broken under cold and warm conditions by crashing it with a hammer on massive support. The results are pieces with irregular shape. To achieve a definite freaking shape the reheated ingot at a temperature over 300 degrees Celsius was notched on one or two sides and broken or split completely by the use of different wedge shaped cutting tools. Therefore bronze hatches or chisels with a plate length of three or four centimeters are used which typically penetrate around a half to one centimeter into the annealed metal. The PCI broken in this way had among others very straight and vertical fracture edges as you can see here. Most of the PCIs were not broken random and irregularly but after certain rules. Many of the round PCIs may have been partitioned according to the principle of a continuing B-section into halves, quarters and eighths. The quarter and eighth pieces were partly divided again resulting in triangular or trapezoid shaped pieces. In addition to the halves there were also narrower circular segments which are separated towards the edge of the ingot by splitting them into thirds middle pieces with quadrangular shape were created. The third partition pattern is the separation of wedge shaped segments which approximately correspond to the sixteenth part of the whole ingot. The last partition pattern are circumferential edge fractions on complete ingots or their quarters resulting in small D-shaped edge pieces. This last partition pattern is very interesting. Why were these edge pieces chipped from the PCI? Is this an easy way for a rapid production of minor quantities of copper for exchange of order or is this a kind of material testing? Let me say here some words about the metal composition of the PCIs and what that means for the practical work with them. The analysis of bronze HPCIs in central Europe revealed that they are originally made of copper with copper, fellow copper or less common and mixed with types. As changeable copper contents and varying amounts of minor elements like ascending antimony and nuclear iron show in poor, partly refined as well as nearly poor and even alloyed copper were used for their production. The chemical composition as well as different contents of copper oxides and sulfides reflected the PCIs are not the result of a coincident manufacturing process. There are products of an entire series of pyramidological processes commencing with copper smelting and continuing with several refining, alloying, recycling and recasting operations while PCIs are being poured and broken up again and again. Particularly annoying in the further processing where higher contents of iron sometimes they lie above 3% per rate. Today you can see this increased iron content through chemical analysis as well as on rust brown patina or by using a magnet. What methods were used to determine the quality of the metal by the agent metallogist? First they can look on the color. Some elements such as ascending iron or here the example with tin pre-changes in the color of the copper. In addition the agent metallogist can test the mechanical properties of the copper by breaking up some pieces and look if the copper is brittle or flexible and so can check the quality for maybe a successful deal. On the other hand the ducheted partition is also an indication that the PCI were bartered and traded after the rate. And so represent a proto pre-monetary currency. Since today numerous attempts have been made to distinguish wheat ratios of PCIs and the fragments in central European hordes but never the different quality of the pieces was taken into account. As well as the fact which show archeological experiments that the PCI is not very easy to divide in very precise rate. With these observations I will finish my presentation. I want to thank the Federal Monuments Authority Austria which funded parts of my research and I will also thank you for your attention. Thanks.