e-conservation the online magazine No. 21, September 2011
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e-conservationthe online magazine No. 21, September 2011
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The fourth of the conferences on the Preservation
of Archaeological Remains In Situ (PARIS) was
held in Copenhagen from 23rd to 27th May. Previ‐
ous conferences have been held in London (1996
and 2001) and Amsterdam (2006). The conferenc‐
es are particularly focussed on the survival of ar‐
chaeological evidence (artefacts, environmental
evidence, stratigraphic and contextual informa‐tion as well as structural remains) when the envi‐
ronment of sites are affected by anthropogenic or
natural changes. Past conferences have focussed
on the nature of the ground environment, how
archaeological evidence changes through time
and what the impact is of short and long term
changes. Much of the earlier discussion was fo‐
cussed on wetland environments and saturated
urban deposits, partly because that was where agreat deal of the observations of change had
been undertaken and also because the impacts
of change were most readily seen in desiccated
wetland soils. There was also a predominantly
northern European bias in the papers presented.
The fourth conference showed a marked broad‐
ening of contributions, both geographically and
in the subject matter. The bias towards Europe
remained, with strong representation from Den‐
mark, the Netherlands, Norway and the United
Kingdom and lesser contingents from Eire, Swe‐
den, Finland, Germany, France, Belgium, Italy,
Portugal, Croatia and Azerbaijan. Single parti‐
cipants were from Turkey, Egypt, Pakistan and
the USA, while the southern hemisphere was rep‐
resented by Australia and New Zealand. PARIS
has become global!
The programme covered a wide range of topics
and was split between four themes:
‐ Degradation of archaeological remains
‐ Monitoring and mitigation case studies
‐ Protocols standards and legislation
‐ Preserving archaeological remains in situ ‐ can
we document it works?
Theme 1, Degradation of archaeological remainsincluded twelve papers. Because of the difficul‐
ties involved in evaluating the results from in vivo
experiments, microcosms in which the range of
variables can be controlled are invaluable and we
were given presentations using this method to
assess the decay rates for wood and to evaluate
impacts on the physico‐chemical and microbio‐
logy of wetlands caused by leaching from wood
treatedwith copper‐arsenic‐chromium preservative.
These were described and included follow up
work in the field to validate the study.
Review by Mike Corfield and Jim Williams
23‐27 May 2011
Copenhagen, Denmark
Organised by:Department of Conservation,National Museum of Denmark
PRESERVATION OF ARCHAEOLOGICAL REMAINS IN SITU (PARIS)
REVIEWS
24 e‐conservation
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Experimental work in the marine or fresh waterenvironment is challenging and this was evident
in papers discussing the impact of erosion and
protection of sites in Lake Constance and Zurich,
a poster presentation on the problems of protec‐
tion on the Gulf coast of Iran, and a major study
of the effects of reburial of metal objects under
seawater as a means of ensuring the survival of
many thousands of artefacts recovered from
shipwrecks at the island of Marstrand, Sweden.The bioerosion of stone underwater is also an is‐
sue and we were shown how rapidly it can be de‐
graded by biological growth eroding the surface
and creating cavities to the extent that surface
detail is lost.
Evaluating the changes to burial conditions by
reference to the stratigraphic layers of corrosion
has been something that one of the reviewers
(MC) has long sought to see tested, so a paper on
this examining corrosion of ferrous artefacts from
an ironworking site in Normandy, France was verywelcome despite the risk of rapid change of cor‐
rosion species following excavation. Unsaturated
soils are notoriously varied and characterising
potential preservation without excavation is often
speculative so a paper reporting work to develop
methodologies for evaluating unsaturated soils
in Oslo was very welcome.
On a broader scale we heard a paper on the carbonrelease arising from desiccation of wetlands and
the risk that archaeological excavations in wet‐
lands might be contributing to greenhouse gas
emissions. The impact of building over archae‐
ological sites was discussed and moves towards
the development of a risk assessment system for
archaeological sites were highlighted. Finally the
question was asked whether preservation can be
predicted from monitoring results, the question
we would all like to see the answer to.
Round‐table participants, from left to right: Jane Sidell, Mark Pollard, Hans Huisman, Jens Rytter, Vicky Richards, Mike Corfield,
Henk Kars, Jim Williams, and standing at and by the podium, Henning Matthiesen and David Gregory, the conference co‐organisers.
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26 e‐conservation
Overall, the papers in this f irst theme were excep‐
tionally broad in their subject matter and scope,
from small scale laboratory work to the large scaleanalysis of an entire urban area. All provided dif‐
ferent methods of quantifying degradation rates
at these different scales, demonstrating that we
have now, collectively, developed a range of tools
suitable for assessing the state of preservation of
most common material. What is less clear, for the
most part, and was not tackled in many of the
papers in this session, are the rates at which de‐
gradation processes are taking place.
Theme 2, Monitoring and mitigation case studies
comprised seventeen papers and again we were
offered a rich mix of papers covering marine and
coastal sites, wetlands and unsaturated sites,
broad scale urban evaluation, and, breaking new
ground (perhaps an unfortunate metaphor for
this conference), studies of the preservation of
sites in the Greenland permafrost and at the other
extreme, in Abu Dhabi, and in addition to ourusual span of materials, mudbrick in China.
It is impossible to cover the details of each of the
papers, but suffice to say that there appeared to
be the recognition that monitoring had to answer
questions, and that only in exceptional circum‐
stances could monitoring be justified over very
long timescales. A report of the important work
at Bryggen, Bergen, Norway demonstrated howpost‐construction monitoring of the impact of
the uncontrolled construction of a hotel at the
World Heritage Site of the medieval waterfront
of Bergen enabled the implementation of post‐
development mitigation of the damages caused
to organic structural remains.
Two papers (one from session 4) showed how
monitoring could be used to devise strategies that
would enable historic towns such as Trondheim,
Norway and Nantwich, England to continue to
evolve to meet the needs of modern life. Interest ‐
ingly, on many of the terrestrial sites presented
under this theme, monitoring was aimed at un‐derstanding unsaturated, rather than fully water‐
logged deposits. Techniques ranged from the use
of TDR, in situ redox and oxygen probes, to soil
and water analysis. Although there was no one
common approach used, the detailed analysis of
soil and water chemistry (anion and cation con‐
centrations for example), before and throughout
monitoring seems to be one of the more reliable
ways of characterising these very challenging
burial environments.
Taking to the water again, we were shown the sad
destruction of the Stirling Castle, one of England’s
finest seventeenth century shipwrecks as it be‐
came increasingly exposed by the movement of
the great sandbank that had hitherto protected
it. It was a graphic example of the challenges in‐
volved in trying to protect entire ships and their
contents in the dynamic marine environment.One of the other elements of the maritime envir‐
onment is wood borers and we were provided
with summary of work in the Baltic Sea, which is
increasing in salinity through the impact of cli‐
mate change as part of the EU project “WreckPro‐
tect” to develop protection strategies against
marine borers for underwater cultural heritage.
On the opposite side of the globe experimental
work to evaluate the options for protecting a19th century wooden hulled ship south of Free‐
mantle, Western Australia were described. In an‐
other departure for PARIS we were shown how
efforts were being made to conserve the extens‐
ive submerged upstanding remains of Roman vil‐
las at Baia, Naples, Italy, and to make them
accessible to scuba divers.
Theme 3, Protocols standards and legislation at‐
tracted fewer papers with eight contributors.
There was a tendency in this session to drift rather
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REVIEWS
Per Kristian Madsen, Director of the National Museum of
Denmark welcoming the delegates and opening the
Symposium.
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Conference breaks provided ample opportunity to share
experiences and exchange ideas.
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too far into straightforward cultural resource
management and this would be a danger for the
PARIS brand which has always tried to focus on
the importance of a sound scientific understand‐
ing to underpin the management of archaeolo‐
gical heritage. Nonetheless, the session did bring
in some new faces who will hopefully have bene‐
fited from the wider programme and who we hopewill return with examples of scientific studies of
the problems inherent in trying to preserve still‐
buried archaeological sites.
Some of the papers in this session reported on
efforts to establish sound management princi‐
pals to underpin their archaeological heritage.
The first paper described how the Norwegian Dir‐
ectorate for Cultural Heritage was using the workit had funded at Bergen to develop a toolbox that
would enable it to apply the same standards so
that the right decisions can be made in future
cases, whilst another outlined the development
of a new governmental body to oversee the ar‐
chaeological heritage of the Flanders region of
Belgium. One paper was concerned with the po‐
tential for soils to be used as indicators of the
preservation potential of sites, using both the soil
itself and its inclusions of, for example, calcareous
shells to indicate the pH of the soil. The paper
argued for more prior assessment of the soils
themselves to influence the design of monitor‐
ing schemes, and perhaps this paper would have
been better placed with the previous theme on
monitoring.
Two projects were concerned with the conserva‐
tion of exposed sites, one a Roman settlement at Ludbreg in Croatia, and the other a mosaic floor
in Turkey. A more seriously misplaced contribution
concerned the need for more coherent strategies
to ensure the proper curation and storage of the
many thousands of dendrochronological cores.
Interesting as these papers were, they were not
really in the spirit of the PARIS conferences and
would have perhaps have generated wider interest
at other venues.
Theme 4, Preserving archaeological remains in situ
‐ can we document it works? was perhaps the most
challenging of all the sessions. It was pointed out
that one of the first attempts to scientifically
monitor an archaeological site was only twenty
one years ago, and this site, the Rose Theatre in
London, has been continuously monitored since
then. This timescale is short by comparison with
the lifetime of most structures built over archae‐
ological remains and it is often hard to tell what
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28 e‐conservation
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changes might take place before they can be re‐
examined. We were given a tour through sites in
London that had been first excavated up to 150 years previously, and when re‐excavated in recent
times were shown to be still in good condition.
However many of these were stone structures
or timber revetments close to the River Thames
where wood preservation has been shown to
be excellent.
The Rose Theatre itself is due to be re‐excavated
and there will be much interest in how effective
the reburial system has been, particularly as it
has become the benchmark for reburial at many
other sites. This was discussed in a paper which
also presented the preferred method for sealing
the site entirely so that the natural hydrology
alone maintains the site’s integrity. Equally in‐
teresting was the research into the impact of a
change in soil moisture content (SMC) that was
presented. It was suggested that a reduction in
SMC from 50% to 40% would to be likely to lead to
a 13% shrinkage in the important deposits of the
Rose Theatre. This is noteworthy as although other
projects have collected moisture data in the past,
few if any have used the data to any great effect.
The continuing information from the research at
Nydam Møse in Denmark was presented, and on a
shorter timescale, there were more results from
the reburial research at Marstrand (the RAAR pro‐ ject also discussed in session 1). The history of
monitoring peat extraction in England’s Somer‐
set Levels coupled with the peat wastage result‐
ing from land drainage was given together with
the hope that nature and archaeological conser‐
vation together with an aging farming community
may enable practical steps to be taken to begin the
long process of regenerating the peat, perhaps
driven also by the beneficial effect this would have
on carbon capture. Farming and drainage were also
critical elements in the management of the land‐
scape around the former island of Schokland. Re‐
sults of the monitoring that has been taking place
for 15 years since 1999 were presented and theefficacy of the various tools used was discussed.
Finally, the evolution of monitoring over 30 years
in England was presented and an assessment of
the types of sites monitored, reasons from moni‐
toring and tools used was given. Recommenda‐
tions to help improve future monitoring projects
were presented. These included the need for more
assessment of the state of preservation of a site
before monitoring is considered; the need for a
proper project design to be developed at the out‐
set of the work; and finally that there should be
clarity about why monitoring is needed for a given
site and what can be done when monitoring data
suggest optimum conditions for survival are no
longer being maintained.
The conference finished with a round table discus‐
sion of the four themes lead by the session chairs.It is hoped that a summary of the main discussion
points raised by the panel and audience will be
collated for the conference proceedings (from
audio recordings). Some of the points discussed
included the extent to which we can quantify de‐
gradation states and rates (states, yes, rates, in
some cases); the need for more ground‐truthing
of model and microcosm research to take place on
actual archaeological sites; the need for morethought to go into designing monitoring schemes,
and for more assessment prior to monitoring; and
finally, a recognition that standards and protocols
can be useful in providing guidance to those
working in the discipline, but often need to be
re‐produced separately for each country due to
different legislation and burial environments.
Just before the discussion started, the session
was interrupted in order for a presentation to be
made to David Gregory and Henning Matthiesen,
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Excursion to Roskilde in Viking ships.
the conference chairs. They were presented with an
award from the Sofie Elizabeth and Aage Rothen‐
bergs Scholarship in recognition of their research
in natural science at the National Museum. We
should also mention the other members of the
organising committee, Karen Brynjolf Pedersen
and Mads Chr. Christensen, who along with Hen‐
ning and David organised an extremely successful
and well run conference.
On the social side, there was an opening reception
in the entrance of the National Museum (the ven‐
ue for the conference) on the evening before the
conference began, a visit to on‐going excavations
in the city centre or a trip to see the ruins under
Christiansborg on the first evening, and the con‐
ference dinner in the Tivoli Gardens at the end of
the second day. The day after the conference itself was over there was an excursion to Roskilde that
included a fleet of Viking ships filled with deleg‐
ates sailing in the bay, and a conducted tour of
the cathedral, and finally, on the fifth (or sixth)
day (depending when you had arrived), an infor‐
mal, guided tour of the National Museum’s con‐
servation department at Mølleådalen near Brede.
The conference proceedings will be published in a
special issue of Conservation and Management of
Archaeological Sites in late 2011 or early 2012.
MIKE CORFIELD
Conservator
Contact: [email protected]
Mike Corfield has been a conservator and conser‐
vation manager in Wiltshire, Wales and with Eng‐
lish Heritage. In 1991 he became responsible for
the hydrological monitoring programme at the
site of the Rose Theatre. Later, he carried out
projects to study the hydrology of sites to increase
understanding of hydrology and the preservation
of organic remains. With their support and like
minded colleagues the first Preservation of Ar‐
chaeological Remains in Situ conference was held
in 1996, and in 1998 recognising that archaeolo‐
gical resource managers recommending mitiga‐
tion strategies needed to be supported by sound
scientific advice and accordingly a team of nine
regional scientific advisers were appointed. Mike
was appointed English Heritage Chief Scientist in
1999, and since his retirement in 2002 he has re‐
tained his interest in site preservation as a con‐sultant, carrying out projects for UNESCO in India
and Iran, and supporting academic research.
JIM WILLIAMS
Archaeological scientist
Contact: jim.williams@english‐heritage.org.uk
Jim Williams is an archaeological scientist, inter‐
ested in preservation in situ issues, specificallygroundwater monitoring and construction impacts.
Jim is a co‐author of the English Heritage docu‐
ment Piling and Archaeology, and has contributed
papers on preservation in situ to a number of
European conferences, and been involved with an
EC project on pile re‐use (RUFUS). During 2009
Jim took a secondment to coordinate the devel‐
opment of a UK‐wide National Heritage Science
Strategy. He is currently the English Heritage
Science Advisor for the East Midlands, a role that
he has undertaken on and off for the last 9 years.