 At first I would like to thank the organizer for having such an interesting session. When I saw the title, I just thought, oh, I've got to be there, definitely. Not especially because I come from Belgium. Well, yeah, Belgium is a small country, but we've got at least chocolate beer and oribirani, of course. But because my research topic is really focusing on glass from this particular period. So as we already said, as we have already heard, the early Middle Ages is really a period of deep changes. This period experienced modification in power, as well as the growing supremacy of the Christian faith that went with the foundation of many churches and a base. Next to them, Amporia also emerged on the coast of the North Sea, and the previous Merovinian agglomeration seemed to be transformed. Indeed, the production activities disappeared from this site and as proved by the work of Joachim Ening, during the Carolingian time, most of the good, most of the artisan production were made in a base or in the rural area and especially in places controlled by the aristocracy. What's also interesting to notice is that the movement of craft production from the previous agglomeration to the rural land goes along with technical changes in this craft. And one of the most emblematic is certainly the one that glass production went through with this change of fluxing agents from soda to potash glass. This change is now documented in two sites from the end of the 8th century, Bad Orbonne and the monastery of Bourne-le-Monsieur. By using a material that was available in Northwestern Europe, glass makers were first able to reorganize the whole production and were able to produce primary glass in Northwestern Europe and so to have a primary glass production at the same place as the production of the object. And then they put an end to their dependency to their re-entire production. However, the mechanisms leading to this change are not well totally understood and next to the shortage in Neutron, the increasing need for architectural glass across Europe could have stimulated this innovation. Indeed, glass discovery has raced in the recent year and facing its importance in early medieval architecture. At the end of the 7th century, churches had real stained glass windows and the walls could have been covered with mosaic. Next to painting and stone, glass played a role in the transmission and the reflection of the light. And in that regard, the colored glass was certainly also an important aspect of the decoration. If window glass is among the first to experience a modification in the recipes, tesserae are going to stay in the Roman tradition and they will long be made with Neutron glass. This certainly implies different production techniques and certainly different production workshops. If remains of secondary production workshops have been discovered among Europe, these testify production mainly of blown glass, of vessel glass or window glass, but there is no evidence of poured glass used for the tesserae production. We've got no workshop producing this small scoop. And even on a broader scale in the Byzantine Empire, there is no known production of tesserae. So how did the artisan obtain the raw material and how did they organize the supply and the diffusion of the cubes? That remains a question. For the early Middle Ages, Leigh James, the specialist of medieval mosaic, emphasized that the 5th and the 6th centuries appear as a high point in mosaic making, at least in Greece, in Italy, and in the Byzantine Empire. Then the number of new mosaics decreased from the 7th century again in the 8th century. The 9th century appears as a resurgence for mosaic making. But for north-western Europe, the site of Germini de Pré is the only one with a mosaic from the early Middle Ages. Still, there must have been much more mosaics in this region because we more and more find these small cubes next to churches and not only the glass cubes, but also remains of mortar where the cubes were inserted. We also have written evidence describing mosaic, for example, the Doha in Toulouse, those of Cologne or Paris. But even with this example, mosaic and tesserae are definitely typical of the Byzantine art and are also widely spread in Italy. So most of the time, Byzantine and Italian artists are mentioned as responsible for the mosaic of the north and the material is also supposed to come from Italy or the Byzantine Empire. Still, on a technical point of view, nothing can exclude a production in north-western Europe. And we dedicated a workshop to this subject and we hope to publish the proceeding by the end of the year. I'm looking at the editors. For the period considered, the glass tesserae correspond to very small fragments of glass. They are generally smaller than one centimeter square and lighter than one gram of glass. The glass tesserae were mainly meant to decorate the walls of the churches. They were made of opaque or translucent glass of various colors. You can have blue, red, green, like a wide range of color but you can also have tesserae covered with metal foil, mainly gold, sometimes silver. For this tesserae, there is a glass base that is mainly colorless but that can also be colored mainly in brown or red. Then a very thin leaf of metal, generally thinner than a few micrometers and the leaf of metal is protected by a very thin sheet of blonde glass. This tesserae are mainly discovered in two types of sites. Mainly places linked to early churches and to the elites and also in palaces. And then, as we've seen previously, they are also found in a workshop. Where they were meant to be remelted and transformed into other objects. During postdoctoral fellowships, I had the great chance to study several sets of tesserae coming from two main areas, one over here and one in the center of France. And this tesserae from Maastricht, Tostes, Tavleaux, Liège, Macron, Uttar, Never and Germany-Deprès were at first studied with macroscopic observation and then analyzed when it was possible in laboratory. Therefore, we use PICCPG method but also micro probe analyzes and allow ICPMS, some of you can recognize, and Andreas Krons from University of Göttingen. When it was possible, we analyzed the different parts of the tesserae too. So, not only the glass but also the gold because it can be relevant according to the work of Elisabeth Anneri and Marco Verita. Finally, we did some portable XRF analysis on the site of Germany-Deprès, directly in situ because if some of the cube were detached from the vault, we couldn't sample, unfortunately, on the others. Now, if you look at the results for the collared glass, according to the work of Nadine Skibil, or Skibil, I don't know. Collared glass is a very specialized production and what she could show for the site, at least for the site of Sagalessus is that the collared tesserae had a glass composition that was typical from the primary glass production and then had a pacifying and coloring agent typical from a secondary workshop. That's for the Roman period. Now, in the early Middle Ages, the picture becomes much more fuzzy. And in our set of data, we could identify for the same color of tesserae different recipes in the same region but also on the same site, for example, at Germany-Deprès. So we've got several options. Of course, the Mosaists could get their cubes from several workshops supposing that these workshops were always working with the same material and with the same recipes. Then it's also possible that due to the recycling, one workshop had several recipes. And finally, there is the recycling and reuse of previous cubes, mainly Roman cubes. Of course, these three options could have been mixed in a random way. If we consider recycling, we are going to look at the opacifying agents and with mainly two types of options. Azo, we've got an antimony-based opacifier. Azo, we've got a tin-based opacifier. In Northwestern Europe, we consider that antimony-based opacifier is typical from the Roman production and then from the 4th century it is going to be replaced by tin-based opacifier that is used for the Merovingian beads as for the decoration of Merovingian vessel. In here, we've got a lot of cubes that are opacified with antimony, mainly for the white cubes, the yellow cubes and the cobalt blue cubes. So these are certainly coming from Roman reuse, Roman recycling. Now, looking at the gold-folied tesserae, we are going to have a quite different picture. In the set that we studied with mainly two types of golden tesserae. These brownish tesserae and these blue-green tesserae. These are chemically totally different, not only because of the manganese that was added in order to get the brown color, but also because of the sand. This set of brownish tesserae was made with a sand that is totally different from the blue-green tesserae. It is shown by the trace coming from the sand. It is also shown by the traces coming from the recycling. And these tesserae are those of the site of Neva that they are dated more or less from the 6th century. Now, the blue-green cube are dated from the 7th century and beyond, and they've got a quite homogeneous composition. In these blue-green cubes, the traces of recycling are quite high, if you look at copper, lead, cobalt zinc and so on. And this is revealing clearly a reuse and remelting of all the glass. Now, we distinguish the two parts of the tesserae and the glass used for the base is different from the glass used to cover the tesserae. The glass from the cartelina is indeed much more clean than the glass of the base. And apparently they selected very cautiously a clean glass in order to have a translucent, transparent sheet. Even if this glass also contains traces of recycling such as antimony, but antimony was not avoided for the cartelina as the other coloring element. Now, we also have got in this glass a lot of manganese and at what one person it was clearly added in order to have this colorless glass. Let's have a quick look at the gold. This is not really the subject of the workshop, but still it's interesting. And we are going to see when we were able to analyze the gold because it's very, very thin. We are going to see that we've got different composition. The gold of Neva is clearly different from the other sheets of gold because it holds a lot of copper. Then the glass of the gold contained a lot of silver and the other sheets are also thicker, about four micrometers, while the other sheets are more thin than one micrometer. And so we've got small differences between the sets. So for the gold foil detestory, if we consider the different part of the glass, we are going to see that we've got different cluster. The one of Neva is clearly different. We can distinguish the production of Germini de Pré with the gold foil. And if we look at the composition of the cartolina, we are going to see that some cartolina are made with a very uncolored glass and some are not. So finally, we've got very distinct group for the gold-folded tessery. Now let's try to make some kind of conclusion about the tessery production and the glass production generally. At first, if we look at the composition of the colorless glass, we are going to see that for the 6th century, we still have an import of fresh glass. We've got very few traces of recycling and the composition of the tessery from Neva seems to fit with the Egypt 2 group. For the blue-green tessery, we've got a composition that we just discussed with Ines Pacta and that seems typical from the HIMT glass but with a lot of recycling. So clearly recycling is increasing. Now what is interesting to notice is that some of the makers of the tessery were able to add manganese in order to get colorless cartolina and the manganese is not used anymore for the production of glass window and glass vessel, at least in the glass from north-western Europe that I could analyze. So these tessery makers certainly add access to other type of material and they can also have access to the gold. If we look at the different set, we see that we've got no real match between the different group of tessery and we couldn't find a perfect match with the tessery from Italy or from the Byzantine world. So this tessery, at least in the state of the art, seems to be a particular production, maybe made on demand for particular churches. And in the 14th century, for example, the gold and tessery from Ovietto were made on the site, especially for the church. Now, reuse and recycling of tessery was definitely practiced. We've got the evidence on several sites. We also have got the evidence in written sources, such as a letter from the Pope Adrian allowing to Charlemagne to take the material, including the tessery, from the palace of Theodoric in order to decorate his own church in Akhen. This tessery also found in ship and it's proven by the analysis that they were reused. They were reused in order to create new mosaic and they were also reused to make new objects. And with a quantity of about one gram of colored glass, these could have been valuable material, especially for some colors. Because some colors, and we discussed that about the cobalt blue beads yesterday, some colors seem quite difficult to obtain, at least in some region and for some period. It's the case of cobalt blue glass. In the Recipes of the Monteophilus cobalt blue glass, at least cobalt blue windows are supposed to be made from Roman tessery. It clearly writes that this tessery was remelted in order to obtain the windows and up until now the analysis seems to prove that. So considering the huge amount of cobalt blue glass that we've got for the medieval period, can we really see that as only resting on recycling? Well, that's a question that we certainly have got to discuss. And then there was a color that seemed difficult to obtain. For example, the yellow and the white. In the Byzantine Empire, at least James noticed that the white glass was replaced by stone. And in a set of data, the white and yellow tessery are very, very rare. And mainly resting on recycling. No, there were a lot, quite a lot, I think of yellow beads and white glass was also quite common in that type of material. And at least for some of the beads, glass makers, beads maker were using a byproduct of metallurgy. So it's quite surprising that the tessery, the people in charge of the tessery, ignored these recipes. And one can wonder what were the exchanges between the artisans in charge of the glass but also between the different artisans working with pirate technology. So that's also, I think, an important point to consider this craft interaction. Some of the artisans may be being closer according to the purpose of the objects that they were making. Again, it's a question that we would like to raise with the River Riches project. In conclusion, to come back to my title and my first question, I would say that tessery are not the result of only local production or only imports. There were certainly several leads in order to obtain the material in order to obtain the cubes. And this option would have varied according to the region and the time, of course, but also to the consumers, to the person ordering the tessery and mosaic. But definitely glass appears as a thing that travels and that will allow us to picture tangible exchanges with the material, but also through the recipes and the techniques, the exchanges of ideas and knowledges. Thanks for your attention.