Northern Archaeology Today issue 10 by York Archaeological Trust

NORTHERN ARCHAEOLOGY TODAY YORK ARCHAEOLOGICAL TRUST MAGAZINE

This issue:

Neolithic Avalon Derby â&#x20AC;&#x201C; Our River, Our City Time & Tide Pontefract Castle Going Purple

Issue 10

ontents

issue 10 December 2016

Welcome! With winter coming in, it is always pleasant to look back on summer days; in this issue we look back on a summer day in 3806BC, as visualised by Marcus Abbott for a new series of videos set in the Avalon Marshes of Somerset. Marcus explains the technicalities of bringing past landscapes (and soundscapes) to life.

Neolithic Avalon

Time and Tide

Our City Our River

Pontefract Castle

Going Purple

We also examine the relationship of Derby (Roman Derventio) to its river, the Derwent; look at the conservation of objects from Pontefract Castle; learn about a new project exploring the coastal landscape near Spurn Point on the extreme eastern tip of Yorkshire, and study the development of Purple Glazed Ware pottery produced at West Cowick near Goole.

Editor: Peter Connelly Layout and design: Lesley Collett (lcollettgraphics@gmail.com) Printed by B&B Press, Parkgate, Rotherham Northern Archaeology Today is published twice a year: UK subscriptions £10.00 per year, Overseas subscriptions £14.00 (sterling) per year. To subscribe please send a cheque (payable to York Archaeological Trust) to: York Archaeological Trust, 47 Aldwark, York, YO1 7BX or telephone 01904 663000 with credit card details. Northern Archaeology Today is published by York Archaeological Trust. Editorial and contributors’ views are independent and do not necessarily reflect the official view of the Trust. Copyright of all original YAT material reserved: reproduction by prior editorial permission only.

Cover picture: Visualisation of an eye-level view along the

England, number 1430801

Sweet Track as it may have looked in 3806BC. (Reproduced with kind permission from South West Heritage Trust)

ISSN: 2049-5897

Neolithic Avalon Marcus Abbott, ArcHeritage

he Avalon marshes are a rich diverse wetland environment located in Somerset. In 2014 the South West Heritage Trust commissioned ArcHeritage to create four animated films to depict the landscape of the marshes over four different time periods, the Mesolithic, Neolithic, Iron Age and Medieval. The area selected for digital reconstruction is home to some iconic archaeological sites such as the Glastonbury lake village and the Neolithic Sweet Track. The wetland conditions have preserved the archaeology of these sites making them unique and important, with a wealth of environmental data. This article will guide the reader through the processes that ArcHeritage used to build the virtual representation of the Neolithic and how we created the final animation and sound-scape.

The initial stage of any digital depiction of the past is information gathering. Collating data on the topography, archaeology and the paleoenvironment enables us to gain an understanding of the natural and human influenced landscape. Five thousand years ago the landscape of the central Brue valley, in which Avalon marshes are situated, consisted of

isolated islands set within a huge reed swamp. On these islands and higher ground, such as the Polden Hills which border the swamp, was primary forest, consisting of oak, lime, ash and hazel. When the first Neolithic farmers settled here they created clearings in the forest and linked the islands to the higher ground by building raised walkways above the water level of the swamp. These wooden trackways ran for kilometres through the swamp, providing a network of routes through the landscape. In 1970 Ray Sweet discovered a trackway whilst ditch cleaning; this discovery became known as the Sweet Track. During the 1970s it was excavated by John and Bryony Coles and the Somerset Levels Project. Much of this trackway is still buried, has been preserved in situ and is now a Scheduled Ancient Monument. Dendrochronology dating puts the construction of the trackway in the spring of 3806 BC; our digital visualisation focuses on this date. Lidar and digital terrain modelling Much of the subject area has existing Lidar (Light Detection And Ranging) coverage, which contains accurate height data, collected

Location of the site. The Avalon Marshes form part of the Somerset Levels, a low-lying coastal plain adjacent to the Bristol Channel bordered by the Quantock Hills and the Mendips. The marshes contain several prehistoric wooden trackways, including the Sweet Track, the Post Track and the Abbotâ&#x20AC;&#x2122;s Way, and the Meare and Glastonbury lake villages

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Lidar image of the Avalon marshes area (looking east). The islands show up as red and yellow on this plot.

using a laser suspended from an aircraft. The laser measures the height of the ground below the aircraft as it traverses the landscape and this information provides an excellent technique for creating accurate surface models of large areas of landscape, and is often used on archaeological projects. The Lidar data obtained for the Avalon marshes area was utilised to identify and map the shape of the high ground, the potential Neolithic islands, in the Brue valley. Using this information we were able to build a large-scale 3D model of the valley. This model formed the basis of the digital landscape. Creating a digital oak tree model. The flow diagram on the right shows some of the multiple characteristics and parameters.

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Building the great oaks of the primary forest and digital ecosystems. During the creative process a digital landscape model such as this will be provided with different designated ecosystems. For example, the primary forest will be on the higher ground and the reed swap will occupy the lower levels of the model. Before these environments could be created we needed to build these ecosystems as 3D models and each plant species required its own digital 3D model. The great oaks of the primary forest are unlike the oak trees we see in the landscape today. The forest oaks of the Neolithic were huge, tall trees

Digital recreation of one segment of the Sweet track alongside a physical reconstruction for comparison.

with a high canopy. Often hundreds of years old, these trees had trunks over 20 metres high before the first branch. A rare surviving example of this type of woodland is the Bialowieza forest in Poland. This primeval forest provided us with a guide to the character and look of the Avalon forests in the Neolithic. The digital version of the Neolithic oak tree is modelled with a range of variable options with multiple characteristics and parameters. This digital tree then becomes the basis of the Neolithic oak species used in the landscape depiction. The computer software can generate multiple versions of the tree using the variable parameters set out at the start. Each single instance of the tree generated by the computer is unique and provides a realistic visualisation of the oak forest. We can then assign the forest ecosystem to the designated areas on the digital terrain and generate a large complex model of the environment. This same technique is used to create the other ecosystems and populate the landscape model with dynamic and realistic digital vegetation. Human intervention and the construction of the archaeology The Sweet Track has a unique construction, being made from crossed wooden poles driven either side of a central rail, the poles in turn supported split planks. Building a convincing digital model of this structure required each

element to be individually distinguishable. A selection of poles, rails and planks were individually sculpted and textured using 3D modelling software. The virtual Sweet Track could then be digitally assembled using these construction materials. We applied the same techniques to build the Neolithic long house and fences creating the elements that make up the Neolithic structures, which are based on known archaeological examples. Whilst we are building these elements we constantly consider how the digital depiction can inform the viewer, such as how we illustrate the underlying construction techniques to show as much of the archaeological information as possible. For example, the wattle showing through the wall of the long house provides a glimpse to the underlying construction of the building. Small details like this feature in all of our reconstructions and are there to provide a depth to the visualisation. Tiling the landscape and building a digital film set With all of the digital elements in place we then divided up the larger landscape model into tiles so that we could create location specific digital film sets. The illustrated example is one of the Neolithic farms which was located at the end of the Sweet Track. This section of landscape includes the digital ecosystems interacting with the reconstructed archaeology. This is a highly complex digital model with northern archaeology today

billions of polygons of detail. Each plant is individual and different from every other plant in the virtual environment. The position of the farm illustrates the forest clearance needed to create areas suitable for growing crops. The stumps of felled trees have been modelled and included in the fields and the occasional tall forest oak left standing alone. Details like this provide extra visual information that enhances the understanding of the landscape situation. Above: Digital reconstruction of a Neolithic longhouse; note the wattle construction protruding through the wall elevation Below: A digital landscape tile illustrating a Neolithic farm at one end of the Sweet Track

The digital set also has environmental elements such as weather, wind and lighting conditions. These add a dynamic realism to the final animation. Artistic direction and the storyboard for the film Once all of the elements were constructed we created a storyboard for the animation to help guide the filming within the digital environments. With Neolithic Avalon our story starts at dawn on a summerâ&#x20AC;&#x2122;s day in 3806 BC. An accelerated sunrise over gently swaying reeds in the breeze is interrupted by the flight of a swan. The camera cuts to the swan and follows the swanâ&#x20AC;&#x2122;s flight over the landscape, revealing the Sweet Track below. This scene provides the context for the track and introduces wetland wildlife to the scene. It also provides a sound reason for the high camera shot, a view of the landscape that is familiar to us but totally unfamiliar to the people of the Neolithic. Scenes like this provide an overview of the landscape and the archaeology within it. A summerâ&#x20AC;&#x2122;s day in 3806 BC and a swan flies overhead.

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Other scenes include a walk through the reeds. This scene starts with a person walking along the trackway and cuts to an eye-level view of walking this route. This scene illustrates new ideas about the landscape and shows that the reeds were close to the trackway, creating a very different experience compared to previous reconstructions which show the trackway in a cleared corridor through the reeds. In the digital animation we can show these multiple ideas at the same time within our reconstructed environment. Beside the Sweet Track archaeologists found several ritually deposited artefacts including a jadeite axe and Neolithic pottery. It was necessary to show these underwater, in situ and alongside the trackway. These underwater scenes also allow the viewer to see the construction of the trackway in addition to the artefacts. We often combine multiple elements of information within a single scene to enhance the depth of information. The animation ends with a scene of the farm showing fields of crops planted around the stumps of felled trees, illustrating how the people of the Neolithic were starting to transform the landscape.

Throughout the whole animation is a soundscape, consisting of recordings from existing environments that are similar to those that would have existed in the Brue valley in the Neolithic. Alongside ambient sounds we added the sound of different species of birds to indicate the variety of wildlife within the landscape. A narrative script was also created and added to the sound track to guide and inform the viewer through the film.

An eye-level view of the Sweet track as it passes through the reed beds.

The Avalon animations are hosted online and will be played in the visitor centre. They represent real places in the landscape and these places can be visited today. The digital reconstructions not only provide a link between the past and the present but also the virtual and the real, encouraging viewers to visit and explore the archaeology of the Avalon Marshes. The animation of Neolithic Avalon, and the other period specific animations can be found on the South West Heritage Trust YouTube channel: https://www.youtube.com/channel/UCgf0BHf5pD9GulfGjbf_3Zg

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Part 1: ‘Neap Tide’ Ian Milsted, Project Manager, York The proverb ‘time and tide wait for no man’ is especially apposite if you live on the precarious parts of England’s east coast. From the crumbling clay cliffs of East Yorkshire to the low-lying flats of Norfolk, the threat of the tide is constant, eroding these fragile coastlines at an alarming rate that may quicken under scenarios of climate change. This is not a new phenomenon, however. If the western margins of the British Isles resemble a fortress, battered by the stormy Atlantic, then the eastern side is softer, less sharply defined, and retains the memory of a time when there was no east coast, and indeed no British Isles. The North Sea is shallow and, geologically speaking, recent. The story of the last 12,000 years has been the loss of the great Mesolithic plains that lay between ‘England’ and ‘Europe’, a place beneath the North Sea that we now call ‘Doggerland’. This story has countless sub-plots: the re-population after the last Ice Age; the importance of the sea for transport, trade, food and security; and the battle to reclaim and protect the land from the water. These stories all leave

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their mark, of course, and YAT’s latest project in East Yorkshire provides the opportunity to investigate the evidence at a very large scale. In March 2015 YAT was appointed to provide archaeological services to a major joint Environment Agency and Associated British Ports project located on the north Humber coast between the villages of Skeffling and Welwick. Close to Spurn Point and popular with bird watchers, the area lies behind the Humber estuary tidal mudflats and consists of low-lying farmland, crossed by natural and artificial water ways that demonstrate the key problem with the land here: keeping it dry. The scheme, which encompasses some 430 hectares (1063 acres), will replace the current flood bank with a new one up to 900m inland and allow the land between the two to gradually revert to saltmarsh and mudflat. The purpose is to create replacement wildlife habitat to compensate for losses due to development and coastal squeeze within the middle to outer Humber estuary. It will also provide a large ‘soft margin’ for flood defence, making the communities of the southern East Riding safer from the potential effects of climate change-related sea level rise and the impact of tidal storm surges, such as those suffered in 2013. This major landscape change, as ever with development projects, represents an opportunity to explore the area’s archaeology in detail. YAT is undertaking an initial evaluation of the scheme area, working alongside the project engineers CH2M in a programme of site investigation works. Our results will then

influence the final scheme design put forward in the planning application. The story we expect to encounter covers the 12,000 years since the end of the last Ice Age at the dawn of the current geological epoch, the Holocene. Understanding the area’s geology will be critical for interpreting the archaeology. There are two major geological features in the project area: the southern edge of the East Yorkshire glacial deposits laid down during the last Ice Age; and a subsequent thick layer of alluvial silts, deposited by the River Humber along the coast, and enhanced in places with land reclamation by a process known as warping. The archaeology will lie throughout this geological sequence, and the huge scope of this project will allow us to appreciate it at a landscape-wide scale. Across much of the scheme, the archaeology of the last 2500 years will dominate the record as intense human and natural erosion of the glacial tills is likely to have obscured much of the evidence for activity prior to the Iron Age. This will still leave a potentially rich resource to explore; a brief glance at the modern map

shows how concentrated settlement in this area begins above the 5m contour. Previous work in this area has encountered extensive Iron Age and Roman landscapes in the same zone and it does not require much imagination to see why; people have always preferred to live above the reach of the storm tide. The medieval history of this area will be familiar to modern residents: the endless battle with the tide. The Humber Historic Environment Record holds the names of several medieval villages known from this area – Orwithfleet, East Somerle, Frismersh and Pensthorpe – but is unable to pinpoint their locations as they were ‘lost to the tide’ many centuries ago. Immediately east of the scheme lies the site of Burstall Priory, also now largely beneath the mudflats of the estuary. Further to the east is Spurn Head, a geological phenomenon in its own right and also the location of the fabled medieval town of Ravenspurn and the port of Ravenser Odd. This is where Henry IV landed during his campaign against Richard II, and was for a time the largest port in northern England, founded on a settlement of Anglian origins with a Viking name. All this was taken by the sea

The project area in detail. Area 4, shaded darker, was added to the project after Areas 1 to 3. Scale 1:50,000

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by the 15th century. In the hinterland of these lost places we may find enough information to understand them better. The story of this landscape is not solely one of loss, however. The western part of the scheme contains two landscape features that have changed beyond recognition in the last 400 years: Sunk Island and the Patrington Channel. If ‘island’ is not enough of a clue, the village of ‘Patrington Haven’ further inland should suggest that once it was possible to sail where we now grow crops. Investigating the thick alluvial deposits in-filling the channel and overlying the south-east coast of Sunk Island provides an opportunity to investigate the postmedieval warping and to locate and explore the archaeology of the former coastlines beneath it.

Lidar data for the project area. Land above c.4.50m AOD in yellow/ red, lower-lying land in green and intertidal area with estuary channel in blue/purple

It is beneath these alluvial deposits that the earliest archaeology may be encountered. The pattern of alluviation is very complex. Although the overall trend since the last Ice Age has been for sea level rise, during this period the climate has fluctuated, and the fact that much of the coastal margin is reclaimed suggests that the tide once reached further inland than it does today. Storm action over the millennia has deposited metres of material beyond the normal tidal limit, and the land itself can be said to have both risen and sunk since the last Ice Age. As the glaciers retreated the land was much lower than today; released from the colossal weight of the ice, the land has slowly rebounded, lifting and draining prehistoric wetlands throughout

the Humber region. The interplay between this and rising sea levels is intricate; add in the effects of erosion as the rising seas flooded the Doggerland plains and continue to eat away at the coast and you have an extremely complicated story to model in detail. Buried amongst this geological complexity is the story of human re-occupation of the land as the ice sheets retreated at the start of the Mesolithic. None of the processes described here was rapid – many thousands of years, and tens of thousands of tides and storms, have influenced the formation of land surfaces, wetlands and beaches. Existing geological boreholes from this region show that at least eight metres of alluvial sediment can be expected overlying the till where the land slips downwards into the Humber estuary. Within this enormous volume of material will be evidence for former land surfaces, now buried many metres down, where people once walked. If preservation is good, then the silts, clays and occasional peats may contain environmental and archaeological evidence for the 10,000 years before even the most rudimentary of historical records are available. Elsewhere along the Humber the evidence for prehistoric activity is stunning: log boats, trackways, and microscopic environmental evidence contribute to a detailed picture of life throughout the turbulent changes described above. The publically available Lidar imagery – created using airborne laser scanning to map the ground heights in detail – shows possible tidal inlets and former river courses; all potential features for prehistoric exploitation. Tackling a complex landscape of this size is a considerable challenge. Not only is the sheer size a factor, but the area encompasses many different landowners and users, all of whose interests must be respected. The landscape itself is difficult to traverse. The fields are irregular, and more usually divided by deep open drains than by hedgerows with conveniently diggersized field gates. Wet weather rapidly makes the clay-rich soils inaccessible to wheeled vehicles, and there are very few access roads large enough

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to deliver tracked mechanical excavators. The area is also important for migrating bird species and site works must avoid disturbing them. Dealing with these challenges requires a fieldwork design that can retrieve the required amount of information with the least amount of disruption. In many ways our approach is traditional – large-scale geophysical surveys and trial trenches targeted to investigate features. However, it is likely that much of the area will not be conducive to geophysics, particularly where the alluvium is thickest, and in any case 430 hectares is prohibitively large to do in one go. Survey is focused where the scheme is likely to impact most, providing critical early information and informing later investigation. Similarly, it will not be possible to trench using the normal approach of covering a certain percentage of the area; this would require many hundreds of trenches which would be extremely disruptive and unlikely to provide proportionally more information. It is not practical to investigate archaeology 7m below the surface with a trench – it would have to be unfeasibly wide to enter safely, and even with shoring it would fill with water. Trenching will be used where glacial till lies up to c.1m below the topsoil, where geophysics is effective and the archaeology can be accessed safely; in practice this will be in the higher areas, where we expect there to be evidence from late prehistory onwards. The deeper archaeology will be investigated with boreholes. The site engineers will use over 100 boreholes to examine the strata from their perspective; we will have access to all their records. Additionally, we will drill 75 of our own boreholes, using a ‘window-sampler’ rig that will allow us to get down to c.10m and record the whole sequence. We will also take detailed environmental samples from the cores and, if suitable material is present, obtain radiocarbon dates. This will allow us to

re-construct the sequence of ancient landscapes across the whole site.

York Fieldwork team working in one of the evaluation trenches

This is the first stage of investigation. As the project progresses opportunities will be explored to involve local communities in the study of their landscape as it undergoes the latest major change in its long history. This will take place alongside continued consultation with the planning authority archaeologist, Historic England and our client as we seek to understand this fascinating and complicated landscape in finer detail. This is a pivotal moment for YAT to take on a project of this nature. In August 2016, the International Geological Congress proposed that the world is transitioning from one geological epoch – the Holocene – to a new age, the ‘Anthropocene’. This new age is defined by evidence of the impact of human activity on our planet entering the geological record, including plastic refuse, chemically changed soils and nuclear isotopes. As archaeologists, analysing human activity is our purpose. Human environmental impact is now being felt most acutely in the form of climate change, which is the driver for the Skeffling scheme. It therefore seems appropriate that through this project we have an opportunity to explore the entirety of the age that is coming to an end, and a chance to set the age to come in context.

Time and Tide Part 2: ‘Spring Tide’ will follow in 2017

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Our City Our River

Excavations in the heart of historic Derby Gareth Davies & Paul Flintoft, Trent & Peak During 2016, Trent & Peak Archaeology (TPA) undertook a large-scale excavation project for the Environment Agency & Derby City Council in the city centre of Derby. The £95 million Our City Our River project will create a kilometre-long piled flood wall, designed to withstand a ‘once in a 100 year event’, along the banks of the River Derwent. Prior to this engineering feat archaeological work was required along key parts of the scheme. Along the flood defence route were two key areas of historic significance. The northern part of the scheme incorporated Little Chester Roman fort (known as Derventio in the Roman period) located at Darley Playing fields (Areas 1 and 3), and the industrial remains were sited around at the southern edge of the scheme (Area 8) close to the Loombe’s Mill, which was the first in the world to throw silk using mechanised

The historic leat of 1692 and revetment wall at Derby’s Silk Mill

The Silk Mill, Derby, looking north. TPA excavation trenches were located immediately to the left of this picture

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production techniques. Given the importance of Loombe’s Mill, essentially the world’s first factory, the building is now the Old Silk Mill Museum and part of the Derwent Valley Mills UNESCO World Heritage Site. Excavation took the form of a continuous trench, 2m wide at the base, along much of the flood defence route. As Little Chester is a Scheduled Ancient Monument, we worked closely with Historic England to maximise the research insights and positive impacts of the scheme. This meant including a large volunteer/community archaeology component (including an excavation on part of Ryknield Street Roman Road) and staff training in the project. To manage the large number of Roman artefacts recovered during the work, we also had the opportunity to enhance many of our systems for undertaking elements of post-excavation on site. Industrial Remains Excavation around the areas of industrial interest provided an opportunity to explore the impact which early industrialisation had on settlement pattern, population growth and the economy of Derby. Trenches at Etruria Gardens (Area 4) revealed well-preserved remains, including the blast furnaces of the Sun and Britannia Foundries, originally constructed in 1822. Moving south, adjacent to St Mary’s Bridge (Area 5), vaulted cellars of a public house and furnaces relating to the Handyside Iron Foundry were discovered. In places these structures truncated deposits

Locations of archaeological interest along the route of the Our City Our River project

containing earlier post medieval artefacts, including kiln wasters from the Derby China Works (c.1767–1848). Excavations on Duke Street (Areas 6 and 7) recovered external walls relating to a 19th-century cement and plaster works, as well as buildings relating to the Union Foundry and Engineering Works At the extreme south of the scheme, investigations around the Old Silk Mill – built between 1717 and 1721 – identified the course of a mill leat, created by George Sorocold, the architect of Loombe’s Mill, in March 1692. The leat allowed water to flow from the Derwent to

the west side of the Silk Mill where the working machinery was later located. Roman Derby and Little Chester Roman Fort Although work in the industrial areas around the Silk Mill produced excellent results, it was the excavation work in and around Little Chester Roman Fort that occupied much of the project’s time and attention. Little Chester fort, thought to have been founded in c. 80AD, is one of two Roman forts in the Derby environs. The first fort was located on higher land, west of the River Derwent, at northern archaeology today

Strutt’s Park. The Strutt’s Park fort is thought to have been a short-lived fort, occupied from c.50AD through to 75/80AD. One theory is that Little Chester was founded as a replacement to Strutt’s Park, perhaps due to the proximity of the later fort to Ryknield Street Roman road, a key artery of trade, exchange and communication in the region.

Derventio, as depicted by William Stukeley in 1721. Image courtesy of Chesterfield Library and www.picturethepast.org.uk

In association with the military occupation Little Chester had an extensive associated vicus (civilian settlement), which was occupied throughout the Roman period. Interestingly a kilometre further east there was another civilian settlement, with an associated cemetery and pottery production centre, at Derby Racecourse. Little Chester Roman fort has been the site of a number of campaigns of archaeological exploration over the years. Notable interventions

include those by the antiquarian William Stukeley in the 1720s, when many of the defences and a ‘gravel’d road’ were evidently extant to the north of the fort. Work by Sherwin in the 1920s, when the area around the fort was turned into a public park, identified the vicus and Ryknield Street north of the fort, and a probable bathhouse to the south. More recently, excavations by Trent & Peak in the late 1970s, in advance of the construction of a Community Centre over the northwest part of the fort, revealed a complex sequence of occupation including possible postRoman deposits. TPA’s recent work (which required 20 archaeologists working on site for six months) offered the opportunity to tie together many earlier observations and also ask new questions of the site. In particular, research questions shifted from resolving issues of absolute chronology (i.e. when was the fort occupied and how this occupation altered over time) to also asking more social questions, such as what activities were taking place in and around the fort, and why. As the team progresses into detailed post-excavation analysis, many of the final observations will undoubtedly be refined; however, some of the key insights concerning the character, chronology and development of this site can be outlined here. The Vicus and Ryknield Street Excavations revealed some excellent new information on the layout and sequence of activity within the vicus to the east and north of the fort. Here, activity commenced in the late 1st century AD. To begin with, in places, boggy ground immediately east of the River Derwent’s floodplain were subject to deliberate land reclamation. As soon as the ground was suitable for habitation it appears that occupation commenced outside the fort, which included timber-built structures and metalled surfaces. The exact nature of this earlier activity is unclear, partly due to an evident major re-planning of the vicus at some point during the 2nd to 3rd century AD. This restructuring was characterised by

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TPA staff Lexy Ellis and Laura Binns with volunteers on the Ryknield Street Roman Road ‘Big Dig’ on the north side of the Vicus

the installation of an east-west aligned road extending westwards from the fort towards the river, which obscured and/or truncated earlier features. As this road progressed eastwards it bisected the north-south aligned Ryknield Street. East of this intersection stone-built domestic and industrial structures were placed at right angles to the routeway. All of this suggests a high degree of order and ‘functional zones’ in the vicus at this time. The notion of distinct functional zones within the established vicus was further corroborated by a number of small finds from metalled surfaces nearer to the fort, including concentrations of coins and brooches which may indicate areas of mercantile activity. In addition, further to the west, an area of pits containing waste residues from smelting and other high-temperature production suggest that the periphery of the vicus was reserved for hightemperature industrial activities as opposed to domestic habitation. The Fort Interior Within the north west part of the fort the team uncovered part of the via sagularis (perimeter road) fronting onto part of a large building (8m wide and 20m long) which may represent a stable block or barracks. Little is known about the demographics of the troops stationed at Little Chester. Intriguing finds from the area of the building, such as a horse-harness pendant with close parallels found in the Balkans,

Looking south at the possible stable/barrack block under excavation in the NW corner of the fort, external foundations in the foreground. The excavation of the building interior is on a systematic grid basis

do raise interesting questions around the potentially diverse ethnic identities of cavalry troops stationed here in the second half of the Roman period. Initial assessment of animal bones and archaeoenvironmental evidence from within the fort has provided some interesting results. Whereas botanical remains from the vicus suggest that the diet of the inhabitants was varied, many from within the fort itself are dominated by only wheat grain. This may suggest that, at times, the occupants of the vicus had access to a much wider variety of locally produced crops when compared to the garrisoned soldiers who only had access to imported wheat. In contrast, many of the animal bones from inside the fort indicate a varied ‘normal’ diet and, as our analyses progress, it may be that we obtain a picture of domestic lifestyles within the fort that change in character over time. Preliminary results from the assessment of ceramic finds appear to indicate that concentrated activity in the fort was curtailed in the early to mid 3rd century. northern archaeology today

The Our City Our River team on the impressively substantial later stone fort wall (3rd century?) which replaced the earlier turf rampart,remains of which are partially visible to the left of the wall

The Fort Defences and approaches Some of the most impressive excavation trenches were located over the northwest fort defensive ramparts. Excavation of the north facing defences and towards the northwest corner of the fort identified a sequence which started with an early turf rampart (1st to 2nd century AD) and seven-metre wide defensive ditches. This rampart was replaced in the 3rd century AD by a substantial rampart topped by a stone wall. A number of ceramic finds from the defensive ditch sequence should allow for a close and accurate phasing of the sequence, once full analysis is complete. One of the most intriguing results concerning the fort defences – and a completely new observation at this site – appears to be that the fort may not have maintained a complete defensive ditch/rampart circuit on its western side: here, the defensive ditches were entirely absent. Instead, the evidence suggests that a natural harbour on the River Derwent, once reclaimed, may have originally been used as the ‘fourth side’ of the fort. In the 2nd or 3rd century AD a re-planning of the fort may then have seen the installation of a formal quayside, suggesting that provision, trade and exchange were increasingly important functions of this site. 14

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A horse harness pendant found in the interior of the fort. Its simple design and decoration are similar to pendants found in the Balkans. Scale 1:1

South of the fort, a previously unidentified Roman road, positioned adjacent to the bathhouse excavated in the 1920s, appeared to lead northwards towards a presumed southern gatehouse area. Interestingly, this road also appears to have been constructed on top of originally boggy ground reclaimed with large amounts of imported ballast. Further analysis will hopefully reveal why such marginal ground was utilised as the location of this Roman fort. It may be that Derventio was founded at this point in the landscape because a suitable harbour could be located here, further highlighting the importance of trade and exchange at the site, alongside military control. Using the evidence gathered during the recent fieldwork, combined with earlier observations, we are now able to create a new interpretative plan of Little Chester Roman fort. This new plan provides an intriguing glimpse of the organisation of the fort and its surrounding landscape in the Roman period. Conclusions and the wider impact of the project The £600,000 programme of archaeological works on the Our City Our River project was

delivered to time and on budget to the satisfaction of Environment Agency and Derby City Council. There were a number of reasons for this, including the fact that from the start the team worked closely with Historic England on the project design in order to maximise the research aspects and positive impacts of the scheme. The creation of a comprehensive research agenda, which included a review of all previous exploration of the Roman fort site, was critical to this process. We were also very pleased that our partners, Black & Veatch, allowed for funding to create bespoke guidance for dealing with the processing and data logging on site of the thousands of Roman artefacts that the excavations recovered. This allowed for the rapid feedback of initial findings into the excavation and recording process, which undoubtedly improved our initial interpretations. Excavation of the western side of the fort and quayside reveals the depth at which Roman deposits were encountered

Preliminary re-interpretation of the fort defences showing both recently excavated areas and the proposed quayside (crosshatched area to west)

Another positive outcome entwined with undertaking post-excavation tasks on site was the comprehensive training and guidance to early-career staff. The whole team benefited from proactive skills development built into the programme and TPA have subsequently been able to retain a number of Our City Our River staff for further fieldwork projects, which has helped create a team bond and continuity. Community and volunteer engagement were also incorporated into the project, resulting in a public excavation on Ryknield Street Roman Road and daily volunteering opportunities for the public. The volunteer element of the Our City Our River project was very successful, with places on artefact processing and places on the â&#x20AC;&#x2DC;Big Digâ&#x20AC;&#x2122; fully filled. We also received excellent coverage via Derby City Council, the local press and BBC Radio Derby. This meant that the project was able to make a positive local impact within Derby and, in discussion with Derby City Council, may yet lead to future interpretative outputs and heritage installations. northern archaeology today

Pontefract Castle A History in Objects

ontefract Castle in West Yorkshire has a long, rich and varied history. Its strategic and geographic position made it a popular and sought-after destination for centuries. During the English Civil War the castle was held as a Royalist stronghold where it was the scene of a series of sieges. It passed into ruin in 1644 and the castle is now a Scheduled Ancient Monument, in the care of Wakefield Council and open to the public. Archaeological excavations initially took place at Pontefract Castle from 1982–86 and were overseen by the West Yorkshire Archaeology Service and the Pontefract Castle Conservation Committee. The archaeological work and primary archive was subsequently published in ‘Pontefract Castle: Archaeological Excavations 1982-86’. Thanks to a Heritage Lottery Fund investment, major conservation and building works are now being undertaken on the castle and artefact assemblage.

The Objects

The artefact assemblage found at the castle is diverse, ranging in date from the Anglo-Saxon period to the Civil War (Roberts, 2002, 35). In late 2015 three separate objects were sent to the Trust for conservation; an iron helmet, iron breastplate and iron wheel (thought to be from a gun carriage). YAT’s role in this project was that of remedial display standard conservation, with the aim of preparing the objects ready for display in the new visitors centre at the castle. These objects had been previously researched and conserved during the initial post-excavation work after the excavations in the 1980s. As an Archaeological Conservator having access to the publication was quite refreshing as we are usually one of the first people to see the finds after excavation. Although only a small sample 16

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Charlotte Wilkinson Assistant Conservator, York of the many objects discovered, these three objects provide an intriguing snapshot into the castle’s history and aspects of the many lives spent there.

Helmet and Breastplate

The helmet and breastplate date to the time of the Civil War. The helmet, which arrived in numerous pieces, has been identified as being of the morion type (Eaves and Hall, 2002). Five of the largest fragments show visible remains of copper alloy rosette washers. The breastplate also arrived in numerous pieces and although it was, like the helmet, incomplete, the pieces were larger making the form of the object more apparent and recognisable. Five of the pieces show clear edges identifying them as arm and neck openings. Stud and swivel hook fastenings also remain towards the top of each shoulder and would have been used for securing shoulder straps. After reading the publication the fragmented condition of both the helmet and breastplate was not unexpected. Each piece was extremely fragile with numerous small fragments sitting loose on the surface in the packaging. The fragments themselves were extremely delicate especially towards the edges, with the breastplate in particular being extremely thin in places. There was visible evidence that the objects had been conserved in the past. The adhesive used to re-adhere sections of both the helmet and the breastplate had started to yellow and become brittle, making the joints weak and fragile, as had the coating which had been applied to some areas of the surface. Small sections in particular around the stud and swivel hook fastenings on the breastplate looked to have been temporarily attached with a blue putty-like substance that was both visible

Consolidating sections of the Air abrading the helmet

and starting to become loose. Although fragile and fragmentary the two objects were found on the whole to be in overall good condition. Areas of active orange powdery corrosion were visible on the surface, however this was in general limited to small spots which could easily be treated. The copper alloy rosettes were still clearly visible on the helmet as were the fastenings on the breastplate. A majority of the surface of the fragments was covered with a brown/orange concretion crust amongst which numerous overlapping mineral preserved organics (MPOs) were visible. MPOs are the remains of organic material, textile, wood or horn for example, which are preserved in the corrosion or concretion products of other objects and are often found on archaeological objects. In some cases they are part of the object, for example a bone handle attached to a knife blade, however, they can also be incidental. The MPOs on the helmet and the breastplate are thought to be incidental due to their fibrous and overlapping nature and therefore relate to the burial environment rather than the object itself. Old joins were taken down with acetone which was applied to the surface using cotton swabs. This successfully softened the joins

wheel

allowing the pieces to be gently pulled apart for individual treatment. On sections where the adhesive was particularly difficult to remove a poultice in the form of cotton wool soaked in acetone was used. The poultice worked well as it meant the acetone could be concentrated on certain areas. Any sections attached with the blue putty were also removed mechanically and a note was made of their positioning. Areas of active corrosion were removed from the helmet and breastplate using an air abrasive machine, which is similar to a small sandblaster. The machine directs a powder at the object in controlled conditions, under magnification, allowing areas of corrosion and concretion to be carefully removed. As the aim on this project was display conservation the concretions were selectively removed to show areas of decoration and construction. The entire metal surface of each fragment was then coated with a solution of 10% Tannic Acid weight to volume (w/v) in 50:50 Industrial Methylated Spirits and Reverse Osmosis water. Tannic acid is a complex organic acid which when applied to iron reacts to form ferric tannate, a porous blue-black film which helps to create a uniform finish and offers a degree of protection to the surface of the object. northern archaeology today

Finally Renaissance Microcrystalline Wax was applied to the surface with a brush to provide a further layer of protection from handling. Fragile areas and MPOs which were left in situ were consolidated with 5% Paraloid B72 w/v in Acetone applied with a brush overall making them more solid and coherent.

Wheel

The iron tyre consists of a set of seven curved rim strakes which join together to form a circular wheel approximately 1.4 metres in diameter. Numerous large-headed nails remain which would have attached the iron tyre to its wooden frame. The Yorkshire Archaeology publication suggests that the functional and plain nature of the wheel implies it is from a gun carriage, as opposed to a civilian vehicle, and proposes that it could have been used at the time of the Civil War siege of the castle in 1644â&#x20AC;&#x201C;65 (Hall, 2002, 352). On arrival at the laboratory it became apparent that although fragile the wheel was in overall fair condition with a majority of the surface being covered by a layer of stable orange and brown concretion crust. Amongst this crust on the underside of the object numerous overlapping sections of MPO wood, probable

remains of the wooden frame, were visible, in particular around the nails. Some areas of active orange powdery corrosion were observed, however this was in general limited to small isolated spots. Due to the size of the pieces not all of them could fit into the air abrasive machine. The corrosion was still removed mechanically, in this instance using steel wool which was carefully brushed against the surface to remove the areas of active corrosion. The metal surface was coated with a solution of tannic acid and the fragile areas consolidated.

Further Work

During this project we had the opportunity to undertake some material analysis on SF4077, a small iron armour fragment from the helmet with a visible lip and decorative floral attachment. Material analysis was undertaken using an Oxford Instruments ED 2000 (EDXRF) at Durham University Department of Archaeology to ascertain the material identification of the rosette washer. We already knew the washer was a copper alloy and were hoping the analysis would give us some more information. Analysis was undertaken at numerous points across the object, an example of the results and spectra can be seen below. The analysis provided the percentage weights of the elemental composition of the material in the form of peaks. As expected a large amount of copper (Cu) was found to be present along with a smaller proportion of zinc (Zn) on all of the results. Copper is therefore a principle component which has been alloyed with zinc, making the rosette washer material likely to be a type of brass. The visible iron (Fe) peak relates to the iron fragment the rosette is riveted too.

Example of the SEM analysis results

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The final stage of the conservation project involved working with a mount maker. When displaying objects a compromise always has to be reached between the objectâ&#x20AC;&#x2122;s needs and the display needs, ensuring the safety and longevity of the object whilst creating a visually appealing and worthwhile display. As a conservator this

Objects being tested in their mounts: (left to right) helmet, breastplate, and all three objects together

is sometimes a challenge as you get heavily involved and attached to the objects during the treatment process meaning handing them over can often be difficult. In this case the mount maker, client and I worked together closely and an excellent result was reached. As evident by the photographs the display will be both visually striking and interesting with the helmet and breastplate displayed in the interior of the wheel. This allows the objects to be displayed to their full potential whilst providing the necessary support for each object.

At the beginning of the project it was decided that no attempt would be made to reattach the individual fragments due to their fragility, and the limited available surface area for the joins. The ‘reconstruction’ aspect was solved by the mounts which hold the individual fragments in position, creating the form of the objects. As the breastplate and helmet are incomplete a metal wire illustrates the outline of the original shape of the objects while small hooks hold each fragment securely in place. The three objects will shortly be going on display at the newly-built visitors centre at Pontefract Castle.

A personal end note from Charlotte:

“

Since starting in the Conservation Department of York Archaeological Trust as a placement student in 2014 I have had the opportunity to carry out conservation work on a number of amazing archaeological artefacts. The work on the Pontefract Castle objects particularly stands out to me, as this was one of the first large projects I undertook after starting my role as Assistant Conservator. I thoroughly enjoyed working on this project and solving the conservation challenges it presented. I look forward to seeing the objects on display in Pontefract Castle knowing that I have played a small role in preserving them for the enjoyment of future generations.

References:

”

Duncan H B, Eaves I, Richardson J, Roberts I, 2002, ‘Artefact Analysis’ in Roberts I (Eds), 2002, Pontefract Castle: Archaeological Excavations 1982-86, West Yorkshire Archaeology Service, Leeds, pp. 135-136. Eaves I, Hall N, 2002, ‘Arms, Armour and Militaria’ in Roberts I (Eds), 2002, Pontefract Castle: Archaeological Excavations 1982-86, West Yorkshire Archaeology Service, Leeds, pp. 324-346. Hall N, 2002, ‘Ironwork from a possible Gun Carriage Wheel’ in Roberts I (Eds), 2002, Pontefract Castle: Archaeological Excavations 1982-86, West Yorkshire Archaeology Service, Leeds, pp. 349-352. Morris C A, 2002, ‘Objects of Wood’ in Roberts I (Eds), 2002, Pontefract Castle: Archaeological Excavations 1982-86, West Yorkshire Archaeology Service, Leeds, pp. 320-323. O’Connor S, Duncan H, 2002, ‘The Bone, Antler and Ivory Artefacts’ in Roberts I (Eds), 2002, Pontefract Castle: Archaeological Excavations 1982–86, West Yorkshire Archaeology Service, Leeds. Roberts I, 2002, ‘Introduction’ in Roberts I (Eds), 2002, Pontefract Castle: Archaeological Excavations 1982-86, West Yorkshire Archaeology Service, Leeds, pp. 300–308. http://www.wakefield.gov.uk/residents/events-and-culture/castles/pontefract-castle/ the-castle-in-pontefract - accessed 21/10/2016 http://canada.pch.gc.ca/eng/1439925170382 - accessed 21/10/2016

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GOING PURPLE New Evidence of Chemical Experimentation by Late Medieval Yorkshire Potters

Tom Watson, MA Material Culture Studies, University of Sheffield

The 15th-century Market At the beginning of the fifteenth century, potters in Yorkshire faced increasingly fierce market competition, both from other potters in the region and from an increase in newlyavailable iron cooking vessels. Large iron cooking vessels had been expensive in earlier centuries, however, the Black Death in the midfourteenth century had resulted in a general increase in wealth and rights among the peasantry, heralding greater consumer demand for such iron vessels. In addition, advances in mining also meant that more iron was available to blacksmiths, bringing down the cost of raw materials and increasing the output of domestic kitchen ware. This period witnessed an increasing rivalry between the sale of iron and ceramic vessels, the eventual outcome of which can be seen in the majority of kitchen pot and pan drawers in Britain today. As a result of this

heightened competition, the fifteenth century saw changes in the forms and appearances of pottery, many of which lasted for hundreds of years. An example of this change was the emergence of darker glazed pottery, the topic of this article, which often displays brown or purple glazed outer surfaces. Humberware Medieval pottery in Yorkshire before the fifteenth century was dominated by highly decorated green-glazed pottery, although changes in consumer tastes had meant that later medieval pottery was much plainer, with an emphasis on function rather than aesthetics. The most common example of this later pottery type in Yorkshire is Humberware, a massproduced green glazed pottery with a wide range of forms and functions. It emerged in

Location of West Cowick

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Left: a Humberware cistern from York (Photo: YAT/Mike Andrews)

Right: a Purple Glazed Ware jug found in Tadcaster in 1946 (Image courtesy of York Museums Trust: http://yorkmuseumstrust.org.uk – CC BY-SA 4.0)

the late thirteenth century and was produced until the start of the sixteenth century. Due to its availability and versatility, Humberware ensured that pottery dominated the domestic market and remained popular in Yorkshire until the end of the fifteenth century. York was one of the largest producers of this pottery type, along with Holme-On-Spalding-Moor and a small village 13 miles west of the Humber estuary called West Cowick . Humberware was produced at West Cowick from the fourteenth century through to the early sixteenth century. Each of the potters in West Cowick would have used large, multiflued kilns capable of firing a substantial number of pots at temperatures higher than those in the previous century. While this in itself provided an advantage in the competitive market place, the temperatures in these larger kilns were harder to regulate evenly, producing more misfired or over-fired pots. The potters either discarded these ‘wasters’, used them as packaging material or, never wanting to miss

an opportunity, sold them as new wares. These “new wares” developed into the second pottery type produced at West Cowick. Purple Glazed Ware To date, excavations in the modern village have revealed West Cowick to be the only known production site to have manufactured the fifteenth-century pottery type now known as ‘Purple Glazed Ware’ in Yorkshire. West Cowick started producing Purple Glazed Ware in the early fifteenth century, and examples have been found dating to as late as the midsixteenth century. This pottery type displays forms that are similar to Humberware, although the majority of examples that have been found relate to small drinking vessels. Purple Glazed Ware’s characterising feature is its distinctive dark, yet shiny exterior which is very different to the green glaze of Humberware. A certain school of archaeological thought had, in the past, attributed the appearance of Purple Glazed Ware in Yorkshire as representing Humberware that had been over-fired. This was due to the northern archaeology today

fact that green-glazed pottery typically darkens at higher kiln temperatures and Humberware was the only other pottery type known to have been produced at West Cowick. Subsequently, West Cowick Purple Glazed Ware has been characterised as a separate pottery type due to the number of examples found on archaeological sites across Yorkshire, including York, in quantities which exceed expectations for â&#x20AC;&#x153;sold onâ&#x20AC;? over-fired pots. This pottery type, while less popular in the fifteenth century than Humberware, turned out to be a relatively radical development in Yorkshire pottery production. While it was not the first darker-glazed pottery in England (earlier examples include Midlands Purpletype Wares) it did outlast Humberware, and was the first in a tradition of darker glazed

pottery produced in Yorkshire that lasted until the nineteenth century. The over-firing hypothesis suggests that Purple Glazed Ware was created by accident. In 2016, as part of my Masters degree, I decided to investigate whether this was truly the case, or whether this influential pottery type was deliberately designed to withstand the increasingly competitive fifteenth century Yorkshire kitchen ware markets. Test the Difference Archaeological material was obtained for this study through the generosity of staff at York Archaeological Trust (YAT) and Doncaster Museum. Fifty sherds from a 1999 excavation conducted by YAT on one of the West Cowick kiln sites were used as the sample for this study.

The chart on the left reveals the startling difference in the iron content between the glazes of Purple Glazed Ware (PGW) and Humberware (HBW) whereas the chart on the right shows that the fabric of the two types of ware are almost indistinguishable

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The image on the left shows a section through part of a Humberware sherd with its relatively clear glaze (the light grey area) and the image on the right reveals the iron oxide crystals in the glaze of Purple Glazed Ware sherd

All fifty (twenty-five Humberware and twentyfive Purple Glazed Ware) were subjected to Portable X-Ray Fluorescence (pXRF) analysis in order to determine the general chemical composition of the glaze and fabric for each sherd. These results then allowed for the selection of ten sherds to be subjected to Scanning Electron Microscopy (SEM), in order to better distinguish chemical differences, and Thin Section Petrography, to determine whether the clay for each pottery type was sourced from the same location. The final test involved refiring part of a Humberware sherd at the temperature to which a Purple Glazed Ware sherd would have been originally fired, to determine whether there was a visual difference between an over-fired Humberware sherd and a standard Purple Glazed Ware sherd. The Results The differences suggested by these results vastly surpassed expectations. The initial test conducted through pXRF suggested that the glaze of Purple Glazed Ware contained 494% more iron than the glaze present on Humberware (which is a lead based glaze), while also suggesting that the fabrics of the two wares were virtually chemically identical.

This latter result was corroborated by the results of the Thin Section Petrography, which suggested that while there were two different types of fabric present in the sample, they were distributed equally between the two types of pottery, meaning that both types were likely produced from the same clays. The SEM data produced results that confirmed a clear chemical difference between the glazes of the two pottery types, as well as producing photomicrographs that displayed a striking visual difference in the cross-section of the glazes (photo above). The photomicrographs of the Purple Glazed Ware samples displayed small dark patches in the glaze, which when analysed further under SEM, turned out to be small concentrations of iron oxide crystals. None of these crystals could be observed in the relatively clear glaze of the Humberware samples, suggesting that the potters had changed something in the composition of Purple Glazed Ware glazes. The photomicrographs obtained under SEM also revealed clues about the temperatures under which the two pottery types were originally fired, suggesting that Purple Glazed Ware was fired at a significantly higher temperature than Humberware. northern archaeology today

of the two pottery types suggests that it is highly unlikely that Purple Glazed Ware was originally created as a result of over-firing Humberware. It could be that as a result of cheaper and more accessible iron vessels entering the market in the fifteenth century, taking market share and threatening livelihoods, potters were experimenting with their proven formulae in order to remain competitive. The metallic sheen of Purple Glazed Ware may also suggest that this was an attempt to mimic the shine of its iron competition. Additionally the increase in firing temperature may have been essential to ensure that the new glaze composition stuck to the clay. As more iron was added to the glaze mixture of Purple Glazed Ware the proportion of lead decreased, which would make it difficult to adhere to the clay at the firing temperatures to which Humberware was subjected.

On the left a Humberware sherd and on the right a Humberware sherd after refiring at 1,175 degrees Celsius. Scale 2:1

Using this information, a small sample of a Humberware sherd was refired in a modern kiln to the temperature which Purple Glazed Ware is estimated to have originally been fired at (around 1,175 degrees Celsius), and the visual difference between the two was immediately clear. The over-fired Humberware sherd displayed a dark brown, almost completely black hue, very different to the glaze of Purple Glazed Ware which has a more purple hue, with a metallic-like shine. What this implies The chemical difference between the glazes

While these 15th-century experiments at West Cowick, if they occurred in the manner stated above, were certainly innovative, they may not have been entirely successful. Purple Glazed Ware was never produced and distributed in the same quantities as Humberware, even though the tradition of darker glazed pottery it was part of outlasted the green-glazed pottery tradition. The scientific and experimental approach to pottery studies outlined in this article may prove to be extremely important for revealing the story behind Yorkshireâ&#x20AC;&#x2122;s lasting glazed pottery traditions. Other more obscure, or less common, pottery types may be hiding innovations yet to be discovered and this approach could unlock these trailblazing stories.

The author would like to thank Anne Jenner, Nienke Van Doorn, and Christine McDonnell at York Archaeological Trust, Peter Robinson at Doncaster Museum and Gareth Perry, Caroline Jackson and Peter Day at The University of Sheffield Archaeology Department for all their support and guidance during this project.

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The Vikings return to York!

Explore more at www.jorvikvikingfestival.co.uk

Join the conversation #JORVIKVikingFest The JORVIK Group is owned by York Archaeological Trust a registered Charity in England & Wales (No. 509060) and Scotland (SCO42846).

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