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  • Final Report Summary - RESTOMO (Reintroducing Stone and MortarMovements, Materials, Methods and Motivations of Builders and Patrons in Early Medieval England, Switzerland and Italy)

Final Report Summary - RESTOMO (Reintroducing Stone and MortarMovements, Materials, Methods and Motivations of Builders and Patrons in Early Medieval England, Switzerland and Italy)

The change in building material and the adoption of new architectural formats is driven at first by a Rome-centred ‘petrifying’ concept of Christianity that permeates society far beyond the building sector. Written sources from 7th century Anglo-Saxon England report that the builders came from the Continent. For these craftsmen, working conditions and resource situation differed immensely from their region of origin. Additionally to the technology transfer, the research project showed, that the pioneer situation led to an adaption of buildings in shape and structure as well as to the development of new technologies that the builders had not employed back home. Lack of skilled personnel, language barriers and independent contracts based on task fulfilment are likely to have been triggers of methodological change. Mortar making technology – especially the distribution pattern and the remains of mechanical mortar mixers – served in the project as archaeological evidence to study the process of ‘petrification’ in early medieval architecture.

On a large scale computer aided 3D-modelling allowed to reconstruct the overall situation as well as the regional and local landscape contexts of early medieval stone buildings. This also allowed to study their visibility in relation to contemporary sites and roads (Monte Amiata, I). On a small scale 3D-laserscanning has been used to document the use of Roman spolia in standing buildings from the Anglo-Saxon period (Hexham Crypt, UK). Remote sensing has been used to search for walls and mortar layers on not or partly excavated sites (Hexham and Wearmouth, UK; Schuttern, D). Scientific mortar analysis and mortar dating has been applied and further developed to understand the specific use of the mechanically produced mortar and the sequence of building phases (Basel, CH; Miranduolo and Donoratico, I).

Northern England (UK), especially the Tyne Valley at Newcastle, has some of the highest densities of early medieval stone buildings north of the Alps, amongst them quite a few that can be dated to the 7th century AD. Typically this first phase belongs to an ecclesiastical context like the double monastery of Wearmouth & Jarrow. On many of the excavated sites traces of a mortar mixers have been found. In this region the sites with mortar mixers tend to be more abundant close to the seashore or at navigable rivers, thus indicating the high importance of waterways as opposed to the land routes from Roman times. The royal castle at Bamburgh is so far the only site with clear indication for the use of animals in mechanical mortar mixing: around the remains of a mortar mixer hoof prints of an oxen were preserved.

In Italy, especially in the old Roman towns, there is no real gap in stone building activity in the Early Middle Ages, but rather a continuation on lower level combined with a turn to the upkeep of existing buildings. In the mountainous densely wooded areas in Tuscany, the local elite builds castles in the 9th/10th centuries. Their early phases are often from wood and they re-erect them in stone as time goes on. For two of the sites that used mortar mixers it was proven that the material from the mortar mixer was used to plaster the outside of the defensive wall (Donoratico) or even the outside of a palisade from wood to make it look like stone (Miranduolo). This indicates that enhancement of visibility has been an important factor that led to the use of mortar mixers. A view shed-analysis of the monastery San Salvatore al Monte Amiata showed that it could have been spotted from long stretches along the pilgrims’ route ‘Via Francigena’ even from as far south as the eastern shore of Lago di Bolsena more than a days’ journey on foot away. The use of mortar mixers in Italy contrasts that of Northern England in so far that in Italy the sites lie on high altitudes inland and date to the castellation phase of the 9th/10th century rather than the low-lying water-oriented Northern English sites, which have with the 7th century a much earlier onset and can be paralleled with the phase that in Italian is called inecclesiamento.

In Northwestern Switzerland (CH) stone building starts only in the 8th century. The situation of sites with mortar mixers is not as topographically determined as in the other two regions. In this region absolute, especially radiocarbon dating of mortar has been attempted in several cases (Basel, Embrach, Lenzburg). For the Basel example several charcoal fragments from the mortar have been dated to around AD 1000 while the mortar itself in an inter-comparison study of several labs repeatedly yielded a Roman date, that doesn’t comply with the stratigraphic situation of the feature. An explanation could be that this is an effect of the reuse of mortar from Roman buildings instead of sand in medieval mortar preparation. Mortar mixers were used in this region for a much greater variety of stone buildings and for longer (Lenzburg, dendro-dated to post 1588) than in the other regions.

In architecture, the replacement or deliberate choice of stone – instead of wood – indicates a process of ‘petrification’ within a society. Often stone monuments are connected with death and notions of eternity, but they can also just intend to be more permanent and through this signal trans-generational possession. ‘Petrification’ can be observed in material culture when more durable, heavier, and inorganic materials are used or in societies when social relations become more stable, hierarchical and predefined. As processes of consolidation and structuring – in nature or in culture, in space or in time –‘petrification’ is an epistemological concept that unites across disciplines and periods in archaeology and connects the humanities with ‘hard’ science.

Dr Sophie Hueglin, Visiting Fellow, Newcastle and Siena Universities,

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