Experimental Archaeology: Making Replica Medieval Coarsewares
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Chewton Mendip Precinct Field Excavations & ‘Origins of Chewton’ Project Experimental Archaeology: Making Replica Medieval Coarsewares December 2018 Pip Osborne BA (Hons) & Jennifer Waters Community Archaeology on the Mendip Plateau (CAMP) Illustrations Cover Pots emerging from the embers (Photo. Rosemary Walker) Figure 1 Chewton Mendip Pottery Fabric Type Series Figure 2 Ham Green sherd from the excavations Figure 3 Coarseware type 31 from the excavations Figure 4 Silts from River Chew bed Figure 5 Shrinkage bars before firing Figure 6 Pots ready for firing Figure 7 Bonfire taking hold Figure 8 The pots emerging from the fire Figure 9 Pots after firing Figure 10 Shrinkage bars after firing Figure 11 Dig field 3 pot and Type 18 of CMFTS unfiled Figure 12 The same sherds filed Figure 13 Naturally occurring inclusions from the Dig field clays Figure 14 Naturally occurring inclusions from the Woodside clays 2 Contents 1.0 Background to Project……………………………………………………4 2.0 Rationale for Project……………………………………………………...5 3.0 Methodology……………………………………………………………...6 3.1 Gathering clays, silts and other inclusions……………………….6 3.2 Preparing the clays ……………………………………………….6 3.3 Preparing the inclusions from the River Chew silts………………6 3.4 Making the Pots and Bars…………………………………………7 3.5 Drying process…………………………………………………....8 3.6 Building the bonfire………………………………………………8 3.7 Firing the pots…………………………………………………….9 3.8 Studying the remainder of the clays for inclusions………………10 4.0 Results……………………………………………………………………11 4.1 Pots……………………………………………………………….11 4.2 Shrinkage Bars……………………………………………………12 5.0 Comparisons with Chewton Mendip Pottery Fabric Type Series………..13 6.0 Discussion………………………………………………………………..15 7.0 Conclusions and Questions arising from our experiments………………16 8.0 Recommendations………………………………………………………. 16 9.0 Acknowledgments………………………………………………………..16 10.0 References………………………………………………………………17 11.0 Copyright Statement……………………………………………………17 3 1.0 Background to Project A field adjacent to the parish church of St Mary Magdalene in the village of Chewton Mendip, Somerset, has been the subject of investigation by members of Community Archaeology on the Mendip Plateau (CAMP) over the past 8 years. Excavations have taken place twice yearly and much evidence has been gathered to support the theory that this was once the site of Saxon artisan activity in connection with a Minster church. Shortly after the Norman Conquest of 1066, the church lands were granted to the Abbey of Jumièges, Normandy, by William the Conqueror. Extensive stone foundations of a multi-phase building cut the artisan soils, and together provide a potential source of evidence of day-to-day living during that period. Much medieval pottery has been recovered during excavation and is thought to date from Saxon times through to the early 15th Century. Such is the importance and interest in this pottery, a Medieval Pottery Fabric Type Series is at present being constructed, comprising some 90 different fabrics (Fig. 1). The majority is of coarseware, with some glazed sherds mainly from kilns at Ham Green and Bristol. The project, being run by members of CAMP, forms a major part of a wider study led by pottery expert David Dawson, assessing whether vessels were manufactured on or near to the site, using local clays, or imported from further afield. This Report details the processes involved in the execution of this experimental archaeology project. Figure 1 Chewton Mendip Pottery Fabric Type Series (part of) 4 2.0 Rationale for Project Glazed pottery of the medieval period has been the subject of study amongst archaeologists over many decades. Kiln sites such as at Ham Green and Redcliff, Bristol and their associated pottery are well documented (Barton, K.J. 1963) (Dawson, D. & Ponsford, M. 2018) However, coarsewares, the everyday vessels of medieval daily life, and of a more utilitarian nature, have not attracted the same interest. The multitude of fabric characteristics, often differing from site to site within a fairly small radius, makes identifying its place of origin very problematic. The main considerations are the clays which make up the matrix of the pots and the inclusions within them, albeit naturally occurring or added by the potter. There is a long-standing belief that different clays behave in different ways and can benefit from the addition of things like quartz, crushed stone, flint, shell, crushed pot (grog) and other additives in order to prevent shrinkage and cracking during firing. Figure 2 Ham Green B ware from Figure 3 Coarseware Type 31 from Chewton Mendip Excavations Chewton Mendip Excavations The variety of different types of clay occurring naturally within the village of Chewton Mendip offers an ideal opportunity for experimental archaeology, to attempt to replicate at least some of the fabrics in the Type Series, using locally sourced materials and firing the vessels in a bonfire for authenticity. With clays collected from around the village during excavations, and inclusions gathered from the bed of the River Chew and other sources, member Jennifer Waters has made a number of similar sized vessels, using different combinations of materials. Once fired, some of the pots were broken and studied under a microscope to look for similarities with our Chewton Fabric Type Series. 5 3.0 Methodology It was decided to attempt to replicate the type of pottery made on a slow, hand turned wheel and fired in a bonfire. 3.1 Gathering clays, silts and other inclusions. Three types of clay were gathered during test-pitting in the village in the Spring of 2018 as follows: Clay 1 Excavation Field: White Lias Formation (pale brown, highly plastic, slightly silty clay with rare sand. Clay 2 Woodside, Lower St: Alluvium (dark brownish-grey, highly plastic with rare silt and fine sand. Probably associated with river deposits) Clay 3 Twyn House, Lower St. Rhaetic, (pale greenish-grey, extremely plastic, very slightly silty clay) Some clay was reserved for study of its naturally occurring inclusions. Additional inclusions were gathered from: Spring head of River Chew, centre of Chewton ST600531 Twenty metres downstream from the Spring head River Chew at Ford ST593536 These were found to comprise quartz, limestone, magnetic fragments and other unidentified particles (see figure 4). Shell and flint was also used (see 3.2.1) 3.2 Preparing the clays Step 1. The clays were kept separate and broken into pieces to remove larger stones and allowed to dry totally. Step 2. The clays were immersed in sufficient water to make a stirring consistency, then vigorously agitated and allowed to settle and excess water to evaporate. Step 3. The clays were kneaded thoroughly to a workable consistency. 3.3 Preparing the inclusions from the River Chew silts Step 1. The gathered inclusions were initially sifted using geological grade sieves of 200-300 and 300-600µm sizes, then dried and bagged. 6 Figure 4 The graded, sieved sands from the River Chew bed The fired-cracked flint was donated by Martin Green from an Iron Age excavation site at Down Farm, Cranborne Chase, Dorset. The land shell was gathered from the Mendip Hills and from the Somerset levels. All was crushed to fine particles. 3.4 Making the pots and bars The pots, of jar form, were made by hand on a slow wheel, comprising 9 pots of various combinations of clays and inclusion and one duplicate. These are detailed in Table 1 below Pot number 1 2 3 + 4 5 6 7 8 9 duplicate Clay source Clay 1 Dig field lower layer √ Clay 1 upper layer √ Clay 1 combined √ √ layers Clay 2 Woodside √ √ Clay 3 Twyn House √ √ √ Inclusions None √ √ √ √ √ Incl. flint and shell √ √ Incl. 200-600µm √ √ NB. Pots 1 & 2. It was postulated that clay may vary vertically in any one location with the topmost layer differing with regards to frequency and type of inclusions. An attempt was made to mimic this by mixing the clay with a lot of water and leaving it 7 to settle naturally. A pot was then made with the top layer and one with the bottom layer. Pots 6 & 9. It can be assumed that any added inclusions would be introduced at the clay mixing stage. In our observations we have noted that these can be poorly distributed across the matrix and in these pots we have attempted to replicate this by insufficient mixing. Nine shrinkage gauge bars were made corresponding to each of the pots. These were marked with a 10cm incision to measure the shrinkage rate. Figure 5 Shrinkage bars before firing nos. 1-6 3.5 Drying process The pots and bars were allowed to dry naturally under cover for several weeks until judged ready for firing. 3.6 Building the bonfire Tree wood was collected for the main wigwam frame with other offcuts of wood donated for the process. The pots and bars were placed 3 over 7 in a bed of hay, on a level layer of wooden slats above a foundation of tree branches. They were then covered in hay and a wigwam built up around them to a height of approximately 0.75m. 8 Figure 6 The pots and bars form base of bonfire 3.7 Firing the pots The fire was lit in several places around the perimeter to allow for a gradual heating of the pots. An intense heat was reached in about 10 minutes from lighting and the fire allowed to die down gradually before retrieval of the surviving pots. The whole process took less than an hour. At the height of the fire the core would be starved of oxygen, causing the process of reduction to take place, resulting in a dark grey or black core to the pot. On dying down, the pot is once again exposed to oxygen causing an element of re-absorption of oxygen or re-oxidisation to the pot surface to take place which turns it a reddish -brown colour.