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)

2

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

3

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

4

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)

5

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.

6

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.

7

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 + duplicate

4 5 6 7 8 9

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

8

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.

9

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.

Figure 7 The bonfire taking hold

10

Figure 8 The pots emerging as the fire dies down with re-oxidisation taking place

3.8 Studying the remainder of the clays for inclusions.

Reserved samples of the clays from the Dig Field and Woodside were finely sieved

(425micron) to remove naturally occurring inclusions which were studied under the

microscope in the post-experiment stage. This process was very informative in

disclosing what inclusions occur naturally in the clay that have been observed in the

Chewton pottery (see 5.1)

11

4.0 Results 4.1 Pots

Seven pots survived the firing process. Of the three pots which didn’t survive, all

were of Rhaetic clay from Twyn House. One left an intact base, the others two

shattered into small pieces.

Of the fully intact pots there were varying degrees of cracking as described below.

Blackening of the sherd surface was apparent on all pots.

Pot number Clay behaviour during firing

1 Horizontal cracks within thicker base. Hairline cracks across

base

2 A few vertical cracks and one horizontal

3 Radiating cracks from larger inclusions occurring naturally.

Hairline cracks in various plains.

4 One small crack across base

5 One horizontal crack on side and two across base.

6 Three vertical cracks.

Figure 9 The pots after firing. Top row 1,3,5, duplicate), bottom row 2,4,6

The spare DF3 pot was broken to study the section in the conventional way. NB No

added inclusions to this fabric.

It can be described as follows:

Core colour dark grey, exterior colour orange buff, interior colour brown buff.

12

Break irregular. External surface feel, rough. Internal surface feel, rough.

Inclusions (microscope @ x10) quartz sparse, quartzite clusters sparse, flint (dark

grey) sparse, rounded bog iron resembling pebbles and magnetic moderate.

Shiny particles, unidentified. Fossil, sparse.

(See figs 11 & 12 for section photos)

4.2 Shrinkage Bars

Of the nine shrinkage bars fired, six survived, corresponding to the intact pots. All

were marked with an incised 100mm line before the drying process proceeded.

Bar/pot

number

Incision length after firing % rate of shrinkage

1 900mm 10%

2 850mm 15%

3 900mm 10%

4 900mm 10%

5 870mm 13%

6 900mm 10%

There appeared to be little correlation between the shrinkage rates and whether there

were added inclusions to the clay.

Figure 10

The shrinkage bars after firing

13

5.0 Comparisons with Chewton Mendip Pottery Fabric Type Series.

Of the surviving bars, 6 were broken and their sections studied under the microscope.

The following observations were made.

Bar/pot no. & site

Core colour Reoxidised Naturally occurring inclusions

1 (DF) Dark grey Yes Sparse angular quartz. Round pebbles. Sparkly particles, shell? Ochre/hematite, Chert

2 (DF) Black Slight Jet black shiny strip-like magnetic particles . Magnesian limestone, sparse lias limestone

3 (DF) Dark grey Some Ditto above + brown magnetic ball

4 (DF) * Dark grey Some Stones, Quartz, Hematite. Sponge-like and coral-like particles.

5 (W) Dark grey Some Frequent lias limestone, Black particles optically same as DF 2

6 (W) Mid to dark grey Some Unevenly distributed bright white speckly appearance. Sparse yellowy-cream lias limestone.

* On applying limescale remover to the broken section there was a release of hydrogen sulphide. This did not happen in the other Dig Field sections nor when applied to the silts which were used as additives. We do not know the cause. The most remarkable similarity between the experimental pots and the those in the

Chewton Fabric Series was with DF3 and Type 18. Whilst the break was slightly

more irregular in type 18, on filing both sherds down the match was strikingly similar,

leading us to believe that there was a strong possibility that clay from the Minster site

had indeed been used to make pottery many centuries ago. However, caution must be

exercised in jumping to conclusions as it could be that the lias clays across a much

wider area have a very closely matching matrix.

Figure 11 Dig Field 3 and Type 18 unfiled Figure 12 The same sherds filed

14

Microscopic study of the inclusions naturally occurring in the clays from both the Dig

Field and Woodside, confirmed that certain particles such as fossils, coral, metallic

elements and minute pebbles, some of which were magnetic, are the signature of the

clays, in addition to the more obvious quartz and limestone and therefore cannot be

considered as additives by potters. These have widely been observed in the Chewton

Fabric Series.

Figure 13 Naturally occurring inclusions from the Dig Field clays, amongst them,

coral, quartz, limestone and other stones

Figure 14 Naturally occurring inclusion from the Woodside clays which includes

magnetic particles showing as black.

15

6.0 Discussion

This experiment was deemed to be a worthwhile and informative exercise. It gave us

considerable insight into medieval pottery making and firing at a time concurrent with

at least some of our Fabric Type Series.

It was interesting to observe how the clays behaved in the firing process. It was felt

that perhaps our pots were fired at too high a temperature, for too long and with too

rapid a rise in heat at the start, causing a complete reduction to take place in the core

of the fabric. We also believe that we were too hasty removing the pots from the

embers and this may have affected the re-oxidisation process. It was also noted that

generally the matrix was of an even texture, without lamination, vesicules and the

waviness often present in the Chewton Series.

Although very limited re-oxidisation took place during the firing process, all the pots

had patchy blackening both internally and externally. This serves as a reminder that

not all blackened sherds were the result of use as cooking pots.

We not only gained a much better understanding of the clays themselves, but also of

the inclusions within the fabrics. By carrying out a methodical and detailed

experiment, logging every process as we progressed, we were able to draw

conclusions about the nature of the Chewton clays. By isolating naturally occurring

inclusions we could immediately identify those which we had previously been noted

within the Chewton Fabric Type Series thus gaining a much deeper understanding of

their composition. This will aid us in inclusion recognition in the future.

The complete reduction in the firing to produce a dark grey to black core also

indicated iron-rich fabrics and this could be a further source of comparison of the

behaviour of our Chewton clays and those in the Chewton Fabric Series.

Attention can now be paid to those sherds in the Chewton Fabric series which do not

have the above attributes, or which have inclusions not naturally occurring in this

region.

16

7.0 Conclusions and Questions arising from our Experiments.

This experiment has opened up the possibility of natural clays having been sourced

local to the excavation site and processed by local inhabitants. This further begs the

question of whether pot making was an artisan activity by one or a few skilled potters,

or whether it was more family-based with skills being passed down through the

generation. This leads us to question where else local clays may have been obtained

and whether certain ‘rights’ were attached to potters or land as in other commodities

ie meadow, pasture, woodland in medieval times. CAMP’s study of the Medieval

strip farming of Hollowmarsh and its ancient origins showed that many landholdings

in Chewton and neighbouring manors had land on the Marsh and that clay is readily

available there.

The sources and signatures of clay matrices is a wider subject than can be addressed

at present, but may have the potential to afford a deeper understanding of the

Chewton Pottery.

8.0 Recommendations

As some of the clays were retained it would be interesting to repeat this experiment

but with a shorter firing time, to a lower temperature and using less fuel. We also

intend to make hand-built pots by differing methods to try and mimic the lamination,

wavyness and uneven textures of some of the Chewton Series associated with the

Saxon period.

It is also intended to extend the gathering of clays to outside Chewton and to include

these in the next phase of the experiment.

9.0 Acknowledgments

CAMP would like to thank the following people for their support

Mr and Mrs Lott, John Croxford and Mr and Mrs Gosland for clay samples.

Mr and Mrs Pullen for use of their garden for the bonfire

Martin Green of Down Farm, Cranborne Chase, for supply of fire-cracked flint

David Dawson for his continued support and guidance in all pottery matters

Brian Irwin for photography

Kay Boreland and Gareth Thomas for expert advice of all things geological

17

10.0 References

Barton, K.J. 1963. A medieval pottery kiln at Ham Green, Bristol. Transactions of the

Bristol and Gloucestershire Archaeological Society 82, 95-126

Dawson, D. & Ponsford, M. 2018. Excavations at Redcliff Hill, Bristol, 1970. Bristol and

Avon Archaeology 27, 49-81.

Dawson, D.P., Jackson, R.G. & Ponsford, M.W. 1972. Medieval kiln wasters from St.

Peter’s Church, Bristol. Transactions of the Bristol and Gloucestershire Archaeological

Society 91, 159-167

11.0 Copyright Statement

Pip Osborne and CAMP retain full copyright of this, and any other report

(commissioned or otherwise), or other project documentation by her under the

Copyright Designs and Patents Act 1988 with all rights reserved. Pip Osborne and

CAMP may however, assign copyright of a document to an interested party upon

written request, but will still retain the right to be identified as the author of the

document as defined in the Copyright Designs and Patents Act 1988 (Chapter IV

s.79). Please contact through the CAMP website in the first instant.

www.camplat.btck.co.uk/contact