Training Reporton
Cultural Heritage Protection
Training Course for Researchers in Charge of Cultural Heritage
Protection in Asia and the Pacific 2003
7 July – 30 August 2003
Nara, Japan

Cultural Heritage Protection Cooperation Office,Asia/Pacific Cultural Centre for UNESCO (ACCU)Preface

In many countries in the Asian and Pacific Region, cultural heritage is at risk of damage
and destruction for various reasons, including: a shortage of human resources for theprotection of cultural heritage, inadequate legal system and a shortage of financial sources.
Under these circumstances, the Cultural Heritage Protection Cooperation Office,Asia/Pacific Cultural Centre for UNESCO (ACCU Nara Office) has initiated various
projects to contribute to the protection of cultural heritage in the region.

Our projects

include organizing training courses, international conferences and symposiums as well asgathering and distributing information.

This time, we provided a Training Course for Researchers in Charge of Cultural Heritage
Protection in Asia and the Pacific 2003, and invited Dr. Nguyen Kim Dung who belongs to
the Viet Nam Institute of Archaeology of the National Center for Social Sciences andHumanities of Viet Nam in the Socialist Republic of Viet Nam.

Viet Nam previously

experienced the calamity of war, and consequently both research institutes and universities
lack human resources with up-to-date sophisticated expertise in the field of cultural
heritage protection.

In response to this problem, the ACCU Nara Office provided this Training Course as a partof the projects to develop human resources for the purpose of ensuring a higher quality ofacademic research and educational activities in the near future in Viet Nam.

We provide

trainees with the opportunity to acquire specialized knowledge of conservation sciences
and scientific methodology required in archaeological study.

Dr. Nguyen Kim Dung has already received her doctorate and is well known as a
researcher of the Neolithic Period in Southeast Asia.

Though she is neither a junior nor

an inexpert researcher, Dr. Nguyen Kim Dung had a longcherished desire to participate iniour training courses because she believed that the specialized training provided would benecessary for setting up the conservation science laboratory which the Viet Nam Instituteof Archaeology is presently planning.

We have therefore decided to invite her to Japan

this year.

During the training course, her enthusiasm and serious efforts to study were highly
appreciated by the lecturers of each organization. With the hope that results of the
training might be transferred, disseminated and actually utilized in Viet Nam as quickly as
possible, a veteran like her is expected to benefit the programme more in a short period
than a younger professional.

We believe that this case suggests that if we consider not only young trainees but also
experienced researchers to participate in the training programmes of the ACCU Nara
Office, results of the training might be visible more quickly.

This Training Course was co-organized with various independent administrative
institutions, in particular, the National Research Institute for Cultural Properties, Nara,
which gave us much support during this training programme.

Many organizations andexperts, including the Archaeological Institute of Kashihara, Nara University and Gangoji
Institute for Research of Cultural Property as well as Dr. Mariko Yamagata of Rikkyo
University also supported us.

We greatly appreciate their help.

October 2003

USHIKAWA Yoshiyuki
Director
Cultural Heritage Protection Cooperation Office,Asia/Pacific Cultural Centre for UNESCO ( ACCU Nara Office)ii

Contents

Preface
1. Introduction ・・・・・・・・・・・・・・・・・・・・・・・・・・・・１

2. Training Programme Report2-1. Participant’s Report ・・・・・・・・・・・・・・・・・・・・・・・ 3−The current situation of conservation science and archaeological survey
in Viet Nam−
2-2. Activity Record

・・・・・・・・・・・・・・・・・・・・・・・・ 7

3. Reference Papers
3-1. An Introduction to the Conservation Science of Archaeological Relics ・・・ 15
3-2. Characteristics of Waterlogged Woods ・・・・・・・・・・・・・・・・ 31
3-3. Recording Methods on Ruins and Relics ・・・・・・・・・・・・・・・ 41
3-4. Archaeological Prospection ・・・・・・・・・・・・・・・・・・・・ 47
3-5. Temperature and Relative Humidity Environmentof the North Section of Shoso-in Repository ・・・・・・・・・・・・・ 65
4. Final Report
Training Course on Cultural Heritage Protection in Asia and the Pacific ・・・・ 67

5. Appendix
5-1. Programme Schedule ・・・・・・・・・・・・・・・・・・・・・・ 77
5-2. List of Instructors ・・・・・・・・・・・・・・・・・・・・・・・ 79

1. Introduction

Introduction

1. About The ACCU Nara Office
In many Asia/Pacific countries, numerous cultural properties are threatened by such risks
as deterioration, weathering, and quick and shoddy repair or incomplete restoration urged
on by the promotion of tourism.

In addition, in many of these countries, the number of

specialists committed to the protection of cultural properties as well as the number ofexperts capable of preserving and restoring these sites are far from sufficient.

To

respond to requests for cooperation from these countries, the Cultural Heritage Protection
Office, Asia/Pacific Cultural Centre for UNESCO (ACCU) was established in August of
1999, as a centre for promoting cooperation in cultural heritage protection.
The office is located in Nara, Japan's ancient capital, where many cultural properties
have been preserved. With cooperation of UNESCO and the International Centre for the
Study of Preservation and Restoration of Cultural Property in Rome (ICCROM), the
ACCU Nara Office organizes training courses for experts in the Asia/Pacific region,
holds international conferences gathering experts and specialists, and collects cultural
heritage information through overseas site survey.

The center is also actively involved

in disseminating information that it gathers through its researches.

2. Providing Technical Support and Specialist Training
We organize various training programs to provide participants with expertise andadvanced technology in the surveying of archaeological remains, preservation andrestoration of wood and stone structures.

We are also involved in teaching conservation

science and other related areas.
The training course for researchers in charge of Cultural Heritage Protection in the
Asia-Pacific region is one of the programs in which the ACCU Nara Office undertakes
every year.

Each year two or three experts from Asia-Pacific region are invited to Japanfor training at appropriate institutions/organizations under the coordination of the ACCU
Nara Office.

13. Vietnamese Expert
The ACCU Nara Office accepted one Vietnamese expert for the first time as a participant
to the training program for Researchers in Charge of Cultural Heritage Protection.

The

specialized training for this year’s visiting scientist included advanced Conservation
Science and Archaeological Survey Method.
July 7th

to August 30

th

The duration for this program was from2003 and included the participation of Dr. Nguyen Kim Dung who

belongs to the Vietnam Institute of Archaeology, National Center for Social Sciences andHumanities of Viet Nam.

4. Training Program
The training program for her had been organized under the cooperation of the
Independent Administrative Institution and affiliated National Research Institutefor Cultural Properties in Nara. Also, several organizations including theArchaeological Institute of Kashihara, Nara University and Gangoji Institute for
Research of Cultural Properties provided an opportunity not only to give lectures,
but also gave open access to use their facilities for a field workshop. The main
survey field workshop was planned at the Nara Palace Site program. Several
changes to the schedule had to be accommodated because of ground surface
conditions at the site caused by inclement weather. Nonetheless, conservation
method and excavation procedure schedules were rearranged and some of thistraining was provided for within the laboratory.

22. Training Programme Report2-1. Participant’s Report2-2. Activity Record

The Current Situation of Conservation Science and Archaeological
Surveying in Viet Nam

Nguyen Kim Dung
Institute of Archaeology
National Center for Social Sciences and Humanities of Vietnam

In Viet Nam, as in other countries of the world, conservation of the cultural heritage andarchaeological research are two important responsibilities for the future. The purpose ofconserving and restoring the cultural heritage, including archaeological ruins and objects, isto maintain them and hand them down to future generations.
In recent years, especially after Viet Nam’s Law for Cultural Heritage Protection was
launched in 2001, conservation science and archaeological surveying have increasingly
developed, and are receiving more attention.

The Vietnamese government has expressed

greater concern for cultural conservation, and given it higher priority, so that in today’ssociety more and more conservation activities are proceeding under the law. According tothis law, archaeological excavation is required prior to any construction work.

At the sametime, with the current trend for regional integration and globalization, Viet Nam has morefavorable opportunities for exchanging ideas and experience regarding conservation work.
Under these circumstances, Viet Nam will certainly receive more help and aid, in terms ofboth financial support and scientific training, from developed countries such as Japan, Italy,
Sweden, France, as well as from international organizations.

1. The Current Situation of Conservation Science in Viet Nam
Because conservation and preservation aims at maintaining the full cultural significance ofmonuments and sites, there are two aspects to cultural heritage conservation andpreservation work: one involving archaeological sites, historic monuments, and examples ofarchitecture in situ, and the other including all cultural objects and artifacts kept in central
and provincial museums.

3

1-1.

There are many cultural sites and monuments needing conservation work in Viet Nam

every year. The processes of modernization and the industrialization of the economy haveexerted a severe negative impact on the cultural heritage, including archaeological sites.
Construction of new roads and new multi-storied buildings is destroying ancient and historicmonuments. Faced with this problem, site protection and conservation work play a crucialrole in the preservation of traditional values. Annually, about 100-200 sites urgently call for
conservation projects.
Although conservation work is conducted according to the needs of particular sites, italso shares common steps. In general, these steps are as follows.
Step 1: Classification of a site based on such criteria as features, situation, function,
value, etc. This specifically includes:• Examination of each site, including surveying, mapping, photographing, andnote-taking, followed by the compilation of documents to certify the site’s
features and value, and its need for protection.
Step 2: Discussion and assessment of the site’s current situation, including careful anddetailed analysis to define the degree of conservation required. This degree mayvary as follows.
• Partial conservation, in which conservation work is applied only to certain
parts of the site, as for example the roof, surrounding wall, pedestal, or
doorstep, or the redecoration of wooden as well as stone monuments. In such
work, priority should be given to traditional techniques and materials, which
are combined with conservation experience from developed countries such
as Japan and Italy.
• Large-scale restoration, to be conducted only when the government permits acall to be made for the participation of specialists from many nations, as well
as experts from international organizations in the conservation field.
Such assessments of the degree of conservation required are made for every partof the site, and ranked in the order of condition and urgency. Next, financial
estimates are made for the conservation work. The best conservation often
involves the least work and can be inexpensive.
Step 3: Determining reasonable methodologies and solutions for conservation work.
Step 4: Making scientific reports to be submitted to responsible agencies.

4

1-2.

With regard to cultural objects needing conservation and preservation, there are morethan 300 museums in Viet Nam where important cultural objects are housed, and theseobjects need to be maintained continually in good condition, using modern techniques ofpreservation.
In actuality, however, only the collections kept in the national museums in Ha Noi and
Ho Chi Minh City are preserved in good condition. By contrast, provincial museums are notsufficiently equipped with modern techniques of preservation or human resources. Generally
speaking, conservation work on archaeological, cultural, and architectural materials in Viet
Nam still faces a number difficulties, such as the following.
•

There are many sites badly in need of conservation and restoration, as many
pagodas, temples and monuments are currently in poor condition.

•

Due to the advancements of archaeological excavation, many sites are being
discovered which require thorough conservation and restoration.

•

Knowledge of conservation science (techniques, procedures, materials) is still
inadequate. Viet Nam must rely on scientific and technical work done by specialists
from other countries, in addition to improving its traditional methods ofconservation and protection.

•

Funding for conservation work remains limited. Almost all provinces lack sufficientfinancial resources to spend on conservation work.

2. The Current Situation of Archaeological Surveying in Viet Nam
As already noted, archaeological surveying in Viet Nam is now being carried out in many
provinces, on every kind of place of cultural significance, from pre-historical to historicalsites. In recent years, surveying is mainly conducted when industrial or other construction isplanned. Almost all archaeological surveys rely mainly on the experience of experts, due totechnological inadequacies. During these surveys, archaeologists often use photography andmanual measurements, instead of modern techniques and surveying equipment.
Archaeological sites are distributed everywhere, in both the lowlands and the highlands,
in mountainous as well as in coastal regions. More open-air sites are discovered andexcavated than underground or underwater ones. Ever year, the Annual National
Archaeological Conference is held in the capital Ha Noi, in which hundreds of newly
discovered sites are included in archaeological reports made to scientists from across thenation. After the Conference, schedules for future surveys and studies are submitted to theGovernment for permission and funding.

5Currently in Viet Nam there are about eight large archaeological projects being
conducted by the Institute of Archaeology, including the following: excavation at My Son
Temple, a World Cultural Heritage recognized by UNESCO in 2000; large-scale excavationin the area of the National Assembly House; surveys and post-excavation work in thehighlands where a hydroelectric station will soon be built. In addition, the Institute issimultaneously conducting archaeological surveys in Hue, Thanh Hoa, and the MekongRiver Delta.
As scientists directly involved in these surveys, we realize that under current conditions
improvements in the techniques employed in our surveys and excavations, and in ourconservation and restoration work, are urgently required for the conservation and protectionof Viet Nam’s national heritage.

Excavation at Tra Kieu site,
Quang Nam Province,
Viet Nam

6

Activity Record
Training for the Expert in Charge of Cultural Heritage Protection in Asia and the Pacific
July 7 to 30 August 2003

Nguyen Kim Dung
Institute of Archaeology
National Center for Social Sciences and Humanities of Viet Nam

July 7 th 2003
• Arrival at Kansai International airport. Met Mr. Nishimura from ACCU Nara Office.
• Visit ACCU Nara Office. Introduction to the members of ACCU.
• Visit National Research Institute for Cultural Properties (Nabunken) and Nara
University – formal introductions. Talked with Mr. Koezuka of Nabunken about
Tektite which is found in impact rock, a raw material for producing stone ornament in
the Bronze Age.
• Professor Nishiyama of Nara University presented a provisional schedule of the
training program, and discussed methods for observing air pollution on cultural
heritage.
July 8 th• Visited the Archaeological Institute of Kashihara (Kashikoken) for formal
introductions. Met vice-director Mr. Nakamura, conservation scientist Mr. Imazu,archaeologist Mr Hashimoto and Mr Kawakami.
• Visited Asuka-Fujiwara Excavation Department and Asuka Historical Museum of
NABUNKEN for greetings.
＜NABUNKEN＞
July 9 th• Started training programme at the Nabunken after meeting with Director Mr. Tanabe of
the Centre for Archaeological Operations, and Head of International ArchaeologicalSite Investigation Section Mr. Tatsumi.
• Introduction to the equipments used at the conservation laboratory. Tour of theseparate archaeological artifact treatment sections for roof tile, wooden artifact andpottery.
July 10th• Lecture by Mr. Kozuma on methods of
examining the material structure ofwooden artifacts and metal objects.
• Introduction to the practice of wooden
artifact examination by using X-Ray
Radiography.
July 11 th (Workshops)• Water content percentage measurementof water-logged wood by using electricbalance meter.
• Temporarystoragemethodofwater-logged wood by sealing inplastic bag.
• Computed Radiography (CR) methodmeasurement by using digital imaging
plate on glass, bronze and textile

7

Water content percentage measurement

Film removal method for soil layers July 14•th(Workshops)
Film removal method for soil layers byapplying synthetic resin at the excavationsite of Daigokuden-in, Nara palace site.
Practice of fragile object removal methodfrom excavation sites by using liquid
nitrogen and the polyurethane foam method.

July 15 th (Workshops)• X-Ray Fluorescence measurement method
for inorganic materials and its application tobronze and glass artifacts.
July 16 th (Workshops)• Video Microscope Camera observation,
Fourie Transform Infra-Red (FTIR) analyses
andportable
X-Ray
Fluorescencemeasurement methods. Examined the eyesof an image of the Buddha Vairocana （廬遮那仏） at Toshodaiji Temple using suchtechniques.
July 17 th (Workshops)• Used the Infra-Red Reflect Graphy measurement method on a fragment of wall
painting to detect invisible description and drawings.
• Lecture by Prof. Sato Masanori on applying the FTIR analyses method to textile andUrushi artifact.
• Traveled from Nara to Tokyo.
July 18 th• Visited the National Research Institute for Cultural Properties, Tokyo.. Met Dr. Saito
Hidetoshi (Director of Japan Center for International Cooperation), Dr. Nishiura
Tadateru (Director of Conservation Department), Dr. Ishizaki Takeshi (section head),
Dr. Aoki Shigeo (Director, Department of Restoration Techniques).
• Introduced to an equipment which can obtain X-Ray Radiography (CR) images using
digital technology in place of conventional film method for large objects andrestoration work on lacquer artifacts.
• Visited Kyushu National Museum (Provisional) located in Tokyo National Museum
and met curators Dr. Kawano Kazutaka and Dr. Kobayashi Koji. Discussed about
ancient technologies of producting food and glass ornaments in Viet Nam, China andKorea.
July 19 th• Attended a seminar in Kokugakuin University and gave a lecture by the theme of “Theevidence of agricultural activities in Phung Nguyen Culture (4500-3500BP)”.
• Met Prof. Yoshida Eiji and an old friend Prof. Tang Chung （鄧聡） of the Chinese
University of Hong Kong （香港中文大学） .
July 20 th• Visited Edo-Tokyo Museum with Dr. Yamagata and Mr. Nishimura.
July 21 st• Returned from Tokyo to Nara with Mr. Nishimura of ACCU Nara Office.
July 22 nd (Workshops)• Water content measurement of wooden artifacts.
• Recorded the current condition of iron artifacts using a digital camera for
documentation before applying conservation science treatment.
Organized these
document records by a card system.

8

July 23 rd• Measured the interior structure of an iron
artifact by stereo X-Ray Radiography. This is apart of the procedure for recording thecondition of an artifact before conservation
science treatments are applied.
• X-Ray Diffraction Analysis used to examine thenature of iron rust by observing the
micro-structure of iron patina. There are two
types of rust: malignant, which causes serious
internal damage and benign, which covers thesurface of objects and acts as a protecting layer
against patina (Inhabitor).
• Practice of measuring and drawing iron
artifacts by hand as a part of documentation
prior to conservation treatment.

X-Ray image observation

July 24 th (Workshops)• X-Ray Radiography taken from separate X-Ray source locations for creating 3-D
images. It is a method for recording the status of patina production on iron artifacts.
• Patina production recording method by hand drawing, using information from the
X-Ray Radiography images.
July 25 th• Lecture on Environmental Archaeology by Mr. Matsui Akira and Dr. Miyaji Atsuko.
• Lecture on Dendrochronology by Dr. Mitsutani Takumi.
July 28 th (Workshops)• Surface observation of iron artifact using a stereomicroscope. Based on theobservation result, the iron artifact was cleaned by applying the Brasive Method,whereby alumina powder was blown onto the artifact, or by using a grinder.
July 29 th (Workshops)• Practice of iron artifact cleaning by the Brasive Method.
• Estimated the amount of PEG impregnated in a wooden artifact by measuring its
weight.
July 30 th• Met Mr. Takahashi Katsuhisa. Discussion on pottery making techniques and materials
for the restoration of pottery in the Section 2 Room of the Nara-Palace Site Excavation
Department, NABUNKEN.
July 31 st (Workshops)• Desalination (salt removal) of iron artifact in a high-temperature and high-pressure
environment using water blended with borax (decahydrate).
• Removed wooden artifacts from the PEG impregnation tank and washed out remaining
PEG residues on their surfaces by warm water.
August 1 st (Workshops)• Resin impregnation into iron artifact.
• Final examination of wooden artifacts by observing distortion unbalance. Organised
the data and information obtained at the NABUNKEN.
＜KASHIKOKEN＞
August 4 th
• Met conservation scientist Mr. Imazu Setsuo, archaeologists Mr. Hashimoto, Mr.
Kawakami, Mr. Matsuda and deputy general of the institute Mr. Nakamura .
• Introduction to Conservation Sciences, bronze mirror surface observation by

9

Bronze mirror surface observation•

digital-microscope, X-Ray Fluorescencemeasurement method and obtaining imagesby the 3-D Laser Scanning method.
Introduction to Sugar-Alcohol (Lactiol)
impregnation method and its application onwooden artifact.

August 5 th (Workshops)• Practised applying the Sugar Alcohol
Impregnation method on wooden artifacts.
• Removal of fragile remains from excavationsites by applying the synthetic resin casting
method.
• Observation of methods for the storage anddisplay of artifacts after conservation
treatment in the institute museum
August 6 th (Workshops)• Practice of Sugar Alcohol impregnation method on wooden artifacts.
• Visit to excavation sites with Dr. Nishiura from National Research Institute forCultural Properties of Tokyo, and researchers from Thailand and Cambodia.
August 7 th
• Visited Karako excavation site with Mr. Hashimoto and Mr. Kawakami. Met Mr. Fujita
and Mr. Mametani who explained about excavation and hosted a tour of the exhibition
room and artifact treatment room.
• Met Mr. Kanekata at the Mizuma Jomon excavation site where small pits anddepression presumed to be associated human habitation were discovered. A measuring
instrument which apply laser beam was introduced.
• Methods displaying plastic copied Haniwa (earthenware artifacts found on mounded
tombs) were observed at Sanryobo Mounded Tomb. The planting of small trees toindicate the original location of the Haniwa artifacts was a good example of site
preservation and information presentation.
• Met Mr. Aoyagi from Kashikoken who is engaged in the excavation at the
Wadanakadori site, where a 5th A.D. settlement consisting of three pit-dwellings havebeen discovered. Although the site is in poor condition, both gray and brown color
pottery artifacts have been found. They are of interest for gaining an understandingof a set of pottery configuration at that time.
• The Ohnoyasumaro tomb area is well preserved by landscaping which encloses the sitefrom the surrounding tea-cultivation field. An inscription plate was found toaccompany this 8th A.D. burial tomb .
August 8 th
• Visited various archaeological sites, including:o mounded tombs that were excavated and preserved by the KASHIKOKENo The ArchaeologicalCenter of Local Authority and Museum, where a study into theconservation and restoration of remains was conducted.
o Sakurai city Archaeological Center.
o Hashihaka tumulus, Hokenoyama tumulus, Nomugi tumulus, Kurotsuka tumulus
and their associated exhibitions.
o Senzuka tumuli Museum.
＜NARA UNIVERSITY＞
August 11 th• Introduction to the effect of Air Pollution on Cultural Heritage by Prof. Nishiyama.
• Methods of observing air pollution. Examples of the effect of pollution on cultural
heritage in the Nara city area were also shown.
• Preparation of filter paper for air pollution observation. Triethanolamine 30 percent

10aqueous solution liquid were used and 25
cylindrical paper filter were made in thispractice session.

Replacement of filter paper

August 12 th• Visited various air pollution observation
points within the Nara city area tocollecting and replace filter papers thatwere placed one month ago.
Sites
visited include:
1. Shosoin Nara Office of theImperial Household Agency; met
1. Mr.
NaruseMasakazu
andreplaced filters in two locations in
the vicinity of the original
Shosoin treasure house.
2. Hannyaji Temple; replacement offilter paper in two locations. Replacement of monthly temperature andhumidity recording paper. The collected data were utilized for calibrating air
pollution measurements by assessing responses to ambient temperaturechanges.
3. Jyuurinin Temple, where a stone Buddha Image is kept indoors. Filter papers
set up beside stone image and outside the building were replaced. Digital dataof the temperature and humidity outside the building were transferred into a
computer. Digital recording device can update and store such data at 5 minutes
intervals for three months.
4. Todaiji Temple Treasure House. Replaced filter papers at three key locations:both inside and outside the Azekura Treasure House and inside a wooden box
kept within the building. Metal plate samples such as silver, copper, tin, leadand iron were also placed in these three locations in an experiment to compare
patina breeding under various conditions of exposure.
5. Todaiji Temple. Filter paper and monthly temperature-humidity recording
paper were replaced at the north-west corner of the main hall and at the northeast corner of the exterior corridor.
Kasuga Shrine. Met the curator Mr. Akita. Replaced filter papers inside the Treasure Hall(Museum), the eastern side of the shrine corridor (natural forest), and behind
the Treasure Hall adjacent to the parking area.
August 13 th• Collected filter samples from the Nara city area, including:
1. the Nara University Library, where filters inside display cases, the reading room andthose in the air pollution observation instrument shelter were replaced;
2. the Instrument shelter in Nara Palace Site area;
3. the Instrument shelter in Yakushiji Temple;
4. inside and outside the Treasure House (Museum) in Kofukuji Temple and the parking
area;
5. the Ichijyo High School campus area along Route 24.
• Preparation for analysis by extracting samples from the filter paper collected.
August 14 th• Extraction of samples from the filter papers in preparation for analysis.
• Set up samples in the Ion-Chromatograhy analyzing instrument.
August 15 th• Analysis of extracted samples using an Ion-Chromatograhy instrument andinterpretation of analyzed data.

11

＜ACCU OFFICE＞
August 18 th• Lecture by Mr. Nishimura on Cultural Heritage Protection in Japan (conducted by the
Agency of Cultural Affaias) and investigation methods in archaeology.
August 19 th• Lecture by Mr. Nishimura on survey methods
Photogrammetry and the 3-D Laser Scanning Method.

inArchaeology

includingAugust 20 th• Lecture by Mr. Nishimura on Archaeological Prospection methods.
August 21 st• Visited Oka Bokkodo (Japanese paper and scroll restoration workshop) in the Kyoto
National Museum, where various analytical and restoration methods were introduced,
including:o Identification of the raw materials for traditional paper making (Mulberry,
Mitumata) by dyeing samples with a homemade dyeing solution and observing
under a microscope. The special paper with gold imprint brought to Japan at c.16 th
century A.D. from Viet Nam was one of the trading items of the Portuguese
Eastern Indian Company.
o Paper damaged by insects are restored by patching with similar paper. This isdone by using machines or by hand, which requires a high level of skill. Glue
used for patching is made of flour and must be at least ten years old, as the use ofstrong adhesive will cause shrinkage and distortion of the original artifact.
• Visited Kyoto National Museum and met curator Mr. Ono Yoshihiro. Importantmasterpieces of South-East Asian origin are kept here.
August 22 nd• Visited Gangoji Institute for the Research of Cultural Property.
• Visited the Conservation Science Laboratory in Ikoma city and met Ms.Ueda Naomi.
As part of the conservation process, wooden artifacts are kept in water prior totreatment. They are then washed and sealed in polyester bags.
• According to the wood species, condition and size of a wooden artifact, an appropriate
treatment method is selected.
Possible treatment methods include PEG,
Freeze-Drying, Sugar-Alcohol (Lactiol) impregnation, Alchol-xylan and theFatty-Acid Ester methods.
• Reapplication of preservation treatment to an iron armour. This artifact had beentreated around twenty years ago but it has begun to deteriorate again. The armour
was carefully dismantled and the bonding materials used in the previous restoration(plaster and synthetic resin) were carefully removed. New treatment was thenapplied. It was a very delicate process.
• Visited the Harimichi site located on the
3-D Laser scanner survey
mountain slope in the Sakurai city area.
Undertook 3-D laser scanning survey on ahistoric stone wall.
• Visited the Nomugi tumulus dated to the
4th century A.D.. A wide moat
surrounding the tumulus containing alarge number of pottery fragments had
been discovered here.
August 25 th• Visited Shoso-in and met Mr. Naruse. An
introduction
totheconservationequipments and methods employed here
were introduced after an inspection of the
Shoso-in building and its natural12•

environment. Methods for the restorationof textile and paper also introduced.
Visited Nabunken conservation laboratoryand discussed about the variety of
instruments available to the Archaeological
Institute in Viet Nam. Instruments forconservation science can be divided into 3
categories corresponding to the stage inwhich they are used and the budget allocated.
These categories are: 1) Basic facility 2)
Analytical instruments 3) Instruments forConservation Science.

August 26 th• Visited the Nara National Museum and met
Mr. Inokuchi.
Exhibits are housed in
special display cases which are resistant toearthquake forces.
Museum exhibition
rooms and storage are maintained at aconstant temperature and humidity (22° and60 percent respectively) for the preservationof artifacts. This is monitored 24 hours bystaff in the central air condition control
room.
• Tri-layer paper boxes are a recent invention– their strength and insulative properties
make them ideal for material transportationand storage. In the past, wooden container
boxes were used, these are evidence of thelong history of material storage traditions in
the museum.

Special paper box

Iron artifact keeping

August 27 th• Visited the Kawarau roof tile production
factory. The factory produces not only
normal roof tiles but also ornamental tiles
which are used on the edges of a roof.
• Visited Zuto, which is located on axis to thesouth of the Todaiji Temple main hall. An earthen pagoda partly covered by roof tile in8th century A.D. is one of the rare example of its type in Japan.
August 28 th• Introduction to the production of publications on research report including printing
techniques by Mr. Nisimura. Photograph and drawing quality in reproduced inpublications rely very much on printing techniques.
August 29 th• Receipt of training course certification from general director Mr. Ushikawa at ACCU
Nara Office.
August 30 th• Departure from Kansai international airport.

13

Japanese Institutions cited:

Nabunken

Independent Administrative Institution
National Research Institute for Cultural Properties, Nara

Tobunken

Independent Administrative Institution
National Research Institute for Cultural Properties, Tokyo

Kashikoken

Archaeological Institute of Kashihara, Nara Prefecture

Nara Univ.

Nara University

Gangoji

Institute for Research of Cultural Property, Gangoji

143. Reference Papers
3-1. An Introduction to the Conservation
Science of Archaeological Relics
3-2. Characteristics of Waterlogged Woods
3-3. Recording Methods on Ruins and Relics
3-4. Archaeological Prospection
3-5. Temperature and Relative Humidity
Environment of the North Section of
Shoso-in Repository

An Introduction to the Conservation Science of Archaeological Relics

KOEZUKA Takayasu
Center for Archaeological Operations,
National Research Institute for Cultural Properties, Nara
Independent Administrative Institution

1. Introduction
The field of using the natural scientific method to investigate, study, preserve and restore precious
cultural properties is called preservation science. There are two types of cultural property,
tangible and intangible. For example, the physical results of applications of technology are
tangible, and the experiential effects of the performing arts are intangible. Preservation sciencedeals with tangible cultural properties, including archaeological materials, works of art,
handicrafts, ancient documents, classical books, and old buildings. As such, objects forpreservation science encompass a wide variety of materials.
This area of science is naturally therefore closely involved with cultural and social sciences,such as archaeology, art history, the history of handicrafts, architectural history, and ethnology. By
approaching cultural properties from the viewpoint of material science, preservation science
makes it possible to provide important information both to cultural science and to social science.
In addition, preservation science is intrinsically associated with almost all fields of natural science,and is growing as a field of study for inter-disciplinary research.
When we consider cultural properties according to the types of materials that they are madeof, we can classify them broadly into three categories. There are organic cultural properties,
which have their origin in the animal and plant kingdoms. There are the inorganic culturalproperties, made of metal or stone. Then there are those made of both organic and inorganic
materials such as metal with wood. Most cultural properties are made from a number of materials,
rather than from one single material.
Excavated archaeological materials are often unearthed in good conditions, although they
had been buried under the ground for a long time. This is probably because the conditions underground, where they had rested for so long, were rather stable. However, although many objects
are found in quite good condition, usually they suffer, at least, some deterioration over the long
period of time in the earth. Then, triggered by changes in their environment through by
excavation, the deterioration of unearthed cultural properties is often hastened. This can result intheir sometimes retaining nothing of the original form that was revealed when they were
unearthed. In particular, this holds true of excavated wooden and iron artifacts. All materials,

15

including archaeological materials, have a life span. That is to say, all material things are facedwith a process of deterioration. Cultural properties reveal a lot of information about the past, andoften have great artistic value. It is important to extend the life of cultural properties and preserve
them as long as possible, without impairing the information and value they contain. Nowadays,
there are many land development projects being carried out throughout Japan and the number ofacademic excavations is also growing. Accordingly, the volume of unearthed relics has become
enormous, to a level beyond our current capacity to treat for preservation.
Here, in this lecture, I will outline the nature of excavated archaeological materials and theapplication of the science that is intended to preserve them for future generations.
For your reference, I will review typical research organizations of this field.
UNESCO (United Nations Educational, Scientific, and Cultural Organization) has
established the International Council of Museums (ICOM) and the International Council ofMonuments and Sites (ICOMOS), non-governmental organizations that promote the preservation
and restoration of cultural properties. There are also governmental organizations, such as theInternational Center for the Study of the Conservation and Restoration of Cultural Properties(ICCROM, also called the Rome Center). There is also an international academic society called
the International Institute for the Conservation of Museum Objects (IIC). In Japan, there are two
academic societies: the Japanese Cultural Properties Society and the Japanese Society for the
Preservation and Restoration of Cultural Properties.

2. Study and Research Methods
2-1 Examining materials
In preservation science, the study of culturalproperties starts with examining the materials. It
is preferable to examine the materials withoutcollecting samples so as to save them fromdamage or destruction. Needless to say, only asmall amount of material should be collected, in
instances when collecting samples is the only
option.
Non-destructive methods for studying
inorganic relics include fluorescent X-ray

16

Fig.1 X-ray fluorescent spectrometeranalysis, PIXE analysis and radio-activation
analysis.

Fluorescent X-ray analysis iscarried out in the following manner. The
sample is irradiated by primary excitation
X-rays. Consequently, the sample generates
characteristic

X-rayspeculiartotheelements it contains. The elements containedin the sample are identified from their placein the X-ray spectrum and their energy.
Fig.2.

Furthermore, a quantitative analysis can be

Non-destructive

X-ray

diffraction

made, by measuring the intensity of the X-rays. The devices used for this research are usually
modifications of standard devices, which vary widely in size and shape. Fluorescent X-ray
analysis is the most widely used investigative technique at present (fig.1). However,radio-activation analysis and X-ray microanalysis, which make it possible to carry out qualitativeand quantitative analyses on a quite small sample, are also often used. In addition, where thecollection of a sample is permitted, atomic absorption spectroscopic analysis and plasma
luminescent spectroscopic analysis are widely used to examine cultural properties. The X-ray
diffraction method is used to identify the mineral composition of oxidized material andearthenware, the deposits on stone statues, and the compounds making up pigments (i.e., theircrystalline components)(fig.2). In Fourier transform infrared spectroscopic analysis andfluorescent spectroscopic analysis, the gas chromatographic mass spectrometer, and theultraviolet absorption spectrum method are used to identify organic remnants such as lacquer,
textile, dye, and resin. You cannot carry out non-destructive (sampling) measurement using anyof the above methods, but they do allow assessment of small sample amounts. The energydispersive X-ray fluorescence analysis device makes it possible to assess extremely small
amounts of material.
2-2 Investigating the inner structure of relics
In order to study and preserve archaeological relics, it is necessary to know exactly what is insidethem, as well as to examine the exteriors of the items. This process is indispensable for clarifying
the techniques used to make the relics, but it help also to obtain the information needed to clean
and restore the relics for preservation. X-ray radiography has become a popular method, in thefield of cultural properties research, for investigating the insides of objects. Recently, computer
image processing has also begun to be used. X-ray computed tomography (CT) which allows you
to obtain a three-dimensional view of the insides of an object has been introduced to the field of
cultural properties research, so it has become possible to obtain much more detailed information.
17

Neutron radiography has also been put to practical use to develop a method for obtaining different
information from that obtained by X-ray radiography.
2-3 Preserving relics in good condition
It is necessary to examine the environment in which excavated relics were buried in order tocreate an ideally safe environment for preserving them in the future. For example, by examining
the environment where an archaeological relic is found, you will be able to learn causes ofdeterioration and weathering. The results of this examination will provide important information
during the investigation of the materials and construction of the relic. Furthermore, thisinformation will also be used to determine optimal conditions (temperature, humidity, andlighting) for storing and exhibiting the cultural property and for designing the storage facility.
In these modern times, metallic and stone cultural properties that are displayed outdoors areoften damaged by acid rain or automobile exhaust fumes. Furthermore, research on measures toprevent damage by mold and insects is also important to creating a good environment for relicpreservation.
2-4 Preservation and restoration
Traditional techniques for preserving and restoring cultural properties have always beenrecognized to be important, as well as the selection of the correct materials and the best
technology. Traditional materials and techniques are particularly emphasized when preserving or
restoring works of art, handicrafts, and buildings. For example, when one repairs lacquered
handicraft items, one should use the same type of lacquer as was used on the object originally.
Ancient buildings are usually repaired and preserved by miya daiku (carpenters who specialize inbuilding shrines and temples), who have learned the traditional techniques.
However, it is not clear how most relics unearthed during excavation were manufactured,and so there are no known traditional restoration techniques. Since the items have already beenchanged because of the physical and chemical processes of aging, it is necessary to use available
preservation techniques that take full advantage of science.

3. The Conservation of Wet Organic Archaeological objects

Organic excavated relics include wooden artifacts, textiles and paper. Wet Wooden objects are themost abundant in Japan. Usually these wooden artifacts are in the form of building members suchas poles, vessels like bowls and stemmed-cups, tools, and ornaments (fig.3). Some wooden
artifacts are lacquered onto a wooden base. Excavators also find wooden tablets bearing
18

characters written in Chinese ink. These organic relics can only survive in the ground in Japan,
where the climate is very humid, if they have been in an environment where bacteria do not thrive.
Most wooden artifacts excavated in Japan have lost much of their cellulose content. Cellulose isof course the chief constituent of wood. A part from cellulose, wooden artifacts contain a lot ofwater, which makes them quite fragile. (Some excavated wooden artifacts consist of 70 per centor more water.)
In most cases, fresh coniferous wood has moisture content of 100 to 300 per cent as muchwater as its solid content, and broad-leaved tree has 300 to 1000 per cent as much water as solids.
Some broad-leaved tree that has become rotten can contain up to 1500 percent as much water assolids. A rotten wood could contain 15kg of water as against 1 kg of solid weight. Wood in thisstate is called “waterlogged wood”, and when it is subjected to natural drying, it shrinks severely,
cracks, or warps.
Excavated organic relics are examined from various aspects and treated to preserve them.
One of the most popular research activities is deciphering characters written in Chinese ink onwooden tablets or lacquered paper. It is often necessary to read characters that cannot be seen
with the naked eye (under visible light) by using an infrared–ray TV camera or an image
enhancement device. These devices are also used for reading characters, symbols, and pictures
written or drawn in Chinese ink on earthenware or metal ware, as well as on wooden artifacts or
paper (fig.4). However, they may not be as effective for reading markings on the harder materials
as they are for reading those on wooden materials. X-ray radiography and X-ray CT are used to
examine the insides of relics, to clarify their techniques of manufacture.
Organic relics are usually less well preserved than inorganic relics, and in most cases only
small pieces of them remain. However, recent advances in analytical devices for examining
organic substances, such as microscopic FT-IR and GC-MASS, make it possible to analyze small
Fig.3. Left: A Japanesemuntins
windowexcavated at Yamadaderasite in Sakurai, Naraprefecture, and a part of
the temple left falling
down was discovered
with enormous quantitiesof building materials of
wood.
All
the
waterlogged wood fromthis site have beentreated by PEG methods.
Right:The reconstructing
a part of Yamadadera
temple in the museum,using the conservationtreatedwaterlogged
wood.

19

samples. With such devices, methods for identifying lacquer, fibers, dye, amber, and tar have been
put into practice, and the progress is being made at clarifying ancient techniques.
3-1. Brief history of wooden artifact treatment
The study of preserving wooden relics has been
going on since times of old. In the 1850s, when agreat number of wooden relics were found on Funen
Island, in Denmark, it is said that an inquiry was
directed to the Denmark National Museum about
how to preserve them. At that time, the museum
recommended the use of potassium alum. About
100 years later a new method, using ether, wasdevised by Christensen of the Denmark National
Museum. In this method, the water in the wood isreplaced by ether, which has a surface tension 1/4 ofthat of water. This prevents the relic from warping
as it dries. Since then, several other methods havebeen developed and put to practical use, using
various types of organic solvents and synthetic
resin.
In Japan, a great many wooden artifacts were
unearthed during the excavation of the Nara
Imperial Palace site, carried out by the Nara
National Research Institute of Cultural Properties.
This excavation triggered the study of scientificmethods for preserving wooden artifacts and has

Fig.

4.
ReflectgraphyofWet
Wooden-tablet Using an Infrared
VidiconTelevision
System.
(left :IR-image, right: normal)

continued for about 20 years. During this period, avariety of preservation methods appropriate for various kinds of relics has been developed. All ofthese methods rely on replacing water held in the wood with a stable substance that will prevent
shrinkage or deformation of the relics while providing them with needed strength. These arecalled the polyethylene glycol (PEG) impregnation method, the freeze drying (FD) method, andthe higher alcohol impregnation method, depending on the substances or methods to be used.
3-2. PEG Method
The PEG impregnation method is the most widely used method, at present. There are various
types of PEG, differing by molecular weight (table 1). The one with an average molecular weight20

Table 1 Characteristics of PEGs
Name
PEG200
PEG300
PEG400
PEG600
PEG1000
PEG1500
PEG1540
PEG2000
PEG4000S
PEG4000N
PEG6000S
PEG6000P
PEG20000

Mean Molecular Weight

200
300
400
600
1000
550
1450
2000
3300
3000
8300
8500
20000

Melting Point(℃)
−
−
−
−
37
40
45
51
56
55
62
62
63

Appearance
clear, liquid
clear, liquid
clear, liquid
clear, liquid
like-wax, solid
paste
like-wax, solid
like-wax, solid
white, flaky solid
white, flaky solid
white, flaky solid
white, powder
white, flaky solidof 4000 is usually used to preserve archaeological waterlogged woods. This type of PEG has amelting point of 55°C and it has a water solubility of 60 (20°C) (100 g/g). This substance is solid
at room temperature. In the PEG method, 5 to 10% PEG solution is put in an impregnation tankwhose temperature can be maintained at about 60°C, and the wooden artifact is put in the tank for
impregnation. The concentration of the PEG solution is gradually increased until theconcentration of the PEG solution reaches more than 95%. When impregnation is finished, theobject is taken out of the solution (fig.5) and returned to room temperature for set-up. At this point,
the water in the wood has been almost completely replaced by PEG, so the object will not shrink
or deform.
3-3. Freeze dry method
In the Freeze Dry method, the water contained in
the waterlogged wood as liquid is frozen solid
and then vaporized (sublimated) under a highvacuum.

When wood is treated using thismethod, the water contained in the wood cannot
move (diffuse internally) during drying, and thewood solids cannot collapse. Thus, there can be
no shrinkage or deformation. Therefore, theshape of the object is safely maintained.
In actual practice, since there is a danger thatFig.5 A large P.E.G. impregnation tank.

the water will expand during freezing and so damage the relics, the water is first replaced withtertiary butyl alcohol. Then, to reinforce the weakened wood, the relic is impregnated with PEG at
a concentration of about 40 to 50% before freeze drying. The texture of the wood is preserved

21when this method is used, and so
this is widely used to treat
wooden tablets bearing Chinese
ink characters. In recent years, a
process

consistingcombination

of

of

a
PEG

impregnation and freeze drying
has been developed to treat large
excavated relics (fig.6).
Recent excavations carried

Fig.6.

The large freeze-drying unit. (Conservation oflog-boat, 5m long)out in low marshy places yielded a large number of wooden relics. Since they had already been
excavated and were therefore vulnerable to destruction, it was necessary to preserve them swiftly.
It takes a long time to complete impregnation using the conventional PEG (quasi-polymer)
method. Recently, various studies have been carried out with the aim of shortening the timerequired to complete impregnation by using especially permeating low-molecular-weightmaterials to reinforce waterlogged wood. The result has been successful in the impregnation ofarchaeological relics using higher alcohol or sugar alcohol. In the higher alcohol method relics are
impregnated with cetyl or stearyl alcohol. Their molecular weights are so small to PEG that the
impregnation time is substantially shortened. In addition, unlike PEG, they are not hygroscopic,
and so the post-treatment storage of relics is made easier. It has also become possible to treat relics
made of composite materials such, as a combination of wood and metal.

4. Inorganic Archaeological Objects (Metals)
Inorganic relics include earthenware, roof tiles, stone artifacts, glass, pottery and metallic artifacts.
These are made of a wide variety of materials. Metallic artifacts pose a great problem due to their
being subjected to corrosion, especially if they have been buried under ground, and they are alsodifficult to protect against oxidation while in storage.
Ancient metallic artifacts are made of many materials. Some are made of a single metal, suchas iron, copper, silver, tin, or lead. Some are made of bronze (copper alloy). There are also
composite relics made of several metals. For example, some relics are copper, plated onto an ironbase. However, almost all metals (except gold) corrode while they rest underground. Corrosion iscaused by the interaction of oxygen, water, and various ions. Chloride ions play a major role in theadvance of corrosion (fig.7,8). Excavated metallic relics are usually scientifically examined as totheir structure and materials, and treated for preservation before being displayed for exhibition or

22

stored in a storehouse according to: "An Outline of theConservation and Restoration of Stone Buildings".
In the study of and research into cultural properties, theshapes and surface of the relics are very important, andtherefore you must not alter their shapes for the sake of
research. In general, when examining relics, non-destructive
tests or microanalysis must be used.
4-1. Examination before treatment
The study of metallic relics usually includes examining theFig.7.
Iron
rust
has
increased rapidly because
the Iron cannon ballrecovered from sea wasnaturally dried.

techniques used to make them and the extent to which they
have corroded. X-ray radiography has long been used forthese purposes. This method was first used in Japan in 1935,
to examine a glass pillow made of glass beads, when the relic
was excavated from the Abuyama-Tumulus in Osaka
Prefecture. Later, in 1978, a sword was excavated from theInariyama-Tumulus in Saitama Prefecture. This method wasused with great success to decipher a 115-character
inscription written in gold inlay on that sword. Since that time,
the use of X-ray radiography has spread rapidly in the studyof buried cultural properties.
More recently, X-ray CT is also used to study relics. Thishas made it possible to observe the items in more detail byobtaining sectional images of an arbitrary part or by
constructing 3-D images.

Fig.8. The bronze disease isformed with the chemical
reaction of copper and thechloride ion.

In addition, with the development of new analytical instruments and advances in computer
technology, methods for examining the materials used to make inorganic relics have also
progressed rapidly. At present, the most popular method is fluorescent X-ray analysis, whichallows non-destructive assessment. In this method, relics are irradiated by X-rays and the types
and quantities of secondary X-rays generated by excitation are measured. With this method, it ispossible to identify several elements simultaneously in a short period. The use of the PIXE
method for examining cultural materials has also been attempted.
However, most metallic relics corrode while they are under ground and their surfaces change
so much that their original composition can no longer be seen. This makes it difficult to interpretthe results of non-destructive analyses correctly. Recently, a fluorescent X-ray analysis device
has been developed that can be used to study micro-areas (100 μm dia.). After an extremely

23small area of a relic is polished, the freshly exposed surface can be analyzed using this device, tostudy the original material.
This method is used not only on metal but also on glass and pottery, to study the history of thematerial and the area from which the material was produced.
4-2. Corrosion
Generally, excavated metallic relics are covered with various type of oxidation. In some cases,oxidation may be suppressed by a coating of oxidized material, while in other cases oxidation
may progress to complete destruction of the original material. To keep the corrosion of relics fromprogressing after excavation, it is usually important to identify the causes of corrosion andremove them, one by one. Generally, the causes of metal oxidation can be divided into two
categories: external and internal.

The external causes include oxygen and water in theenvironment. The internal cause is soluble salts contained in secondary products (such asoxidized materials) adhering to the relics. You can learn about the history of relics and whether
the corrosion of a relic will progress further or not, by analyzing these secondary substances.
Iron relics are usually covered with oxi-iron hydroxide. The oxi-iron hydroxide found on
excavated objects are of three types: α, β, γ-FeOOH. β-FeOOH is generated in the presenceof chloride ions and poses a particular problem for preservation. This corrosion product was first
discovered by Matsuo Nambu, inside an iron meteorite, about 30 years ago. After that, it wasreported that β-FeOOH is present in excavated iron relics (fig.9) and that it is caused by chloride
ions (Makoto Shima and Hideo Yabuki, 1979). At present, before preservation, the oxidation oniron relics is identified by X-ray diffraction. In addition, to determine the treatment method, thepresence of chloride ions and anions such as sulfide ions, fluorine ions, and nitrate ions areanalyzed quantitatively. Chloride ions are a major cause of the advance of corrosion on relics(especially in Japan, where the relative humidity is so high), and so they should be removed (i.e.,the object should be desalted) to the best extent possible. There are two methods for desalinatingiron relics: the dry and the solution (or washing) methods. The solution method is popular inJapan. The alkaline solution method is one that is widely used. The use of a high-temperature andhigh-pressure device (autoclave)(fig.10) has also been
investigated as a means of extracting chloride ions andsulfide ions. Iron relics that have been chemicallydesalted using one of these methods are thenimpregnated with acrylic resin as a means ofreinforcement and to block air from reaching the relic,to prevent oxidation.

24

Fig.9. β-FeOOH, “AKAGANEIT” This
corrosion products was foundfrom inside of sword.

4-3. Bronze disease
Copper and bronze relics, as well as iron relics, corrode anddegrade in the presence of chloride ions. For example, bronze
mirrors that seemed stable when excavated, often corrode withina period of some few dozen odd years, and end up withdegradation of the entire object. This phenomenon, when it
occurs to bronze relics, is called “bronze disease”. Copper
chloride or basic copper chloride is detected in the corrosion thatdevelops on bronze relics. The non-destructive X-ray diffraction
device with parallel beams can be used to obtain diffraction data
about corrosion without damaging a precious cultural property,
contributing to the early detection of bronze disease.

Fig.10.
The High-temperatureandhigh-pressuredevice.
Chloride
removalforiron.

4-4. Iron corrosion
Bronze disease can be prevented by removing the causative substance, the chloride ions. However,
the removal of chloride ions from bronze relics is difficult in most cases, because there is often arisk of causing changes to the color of the relic or damaging it in other ways. Therefore, bronze
relics are usually protected from chloride ion attack by giving them a protective film over fresh25

metal to prevent the progress of corrosion. This is called the benzotriazole method (fig.11), a typeof chemical protection. It is generally used for treating excavated copper and bronze relics.

5. Preservation of archaeological remains
Excavated remains are often reburied to preserve the site and its contents. If there arearchaeological structures that would be difficult to rebury in the state they were before excavation,
they are removed from the site and treated to preserve them.
However, it is ideal if the entire archaeological find can be preserved in-situ without either
reburying it or removing it from the site.
5-1. Preservation of archaeological feature
If the soil is dry, houses and kilns can be reinforced and stabilized by impregnating them withsynthetic resin or other materials. However, considering the vulnerability to weathering ofsynthetic resin, and the layout of archaeological features, it is not easy to preserve them if they are
exposed. Generally, archaeological features are exhibited or preserved under a protective facility,
such as an overhead structure, in addition to being impregnated with synthetic resin. Kilns often
have deteriorating ceilings. If this is the case, the ceiling may be partially restored to help
reinforce and support the kiln wall. The ceiling is usually restored using lightweight, somewhat
flexible polyurethane foam. By partially restoring the ceiling, the structure of the kiln can be
specifically revealed. This method therefore enhances exhibition and preservation at the sametime.
5-2. Environmental control
Ancient sites may become degraded or even encroached by robbers, so methods for preserving or
restoring them will vary according to situational demands. The Takamatsuzuka remains (in Nara
Prefecture) are an example of a situation where complete preservation measures were taken. This
site attracted attention among the Japanese people because there were still pictures remaining on
the walls. It was considered important to restore the stone chambers based on the environment
they had been in before excavation. For this reason, a total control system was installed so that thetemperature and humidity inside the chambers could be maintained as they had been before the
excavation. To preserve the remains, due consideration had to be taken of the structural dynamics
of the stone chambers, and care had to be taken to prevent the growth of bacteria and mold,stimulated by the high humidity inside the stone chambers. Of course, since conditions vary at
different sites, appropriate measures must be taken, suitable to the particular situation.

26

5-3. Reduced pressure impregnation
Large- sculptures carved in rock outcroppings, such as stone Buddhist images carved in cliffs, areimportant artifacts. Rocks are exposed to earth and weathering. They can suffer damage due tophysical and chemical actions caused by temperature changes and the effects of water. With
weathering, rocks can develop many gaps and absorb a lot of water, as well. They will therefore
be physically damaged by the actions of the freezing and melting water. For this reason, an
impregnation-reinforcing material is injected into stone outcrop Buddhist images, to protect them.
The impregnated material lowers the water permeability of the rocks. Dipping, continuous
spraying, pressure reduction, or pressurization is used to force the preservative material into rocks.
Reduced pressure- impregnation can be used no matter what the shape or size of the object, and is
widely used to preserve irregular shaped archaeological pieces, including stone Buddhist images
carved into cliffs.

6. Moving materials as a means of preserving them6-1. The removal of fragile archaeological remains from the excavation siteArchaeological relics found during excavation are usually oxidized or decayed and so, if they are
removed from the site as they are, their integrity might be destroyed. On the other hand, there aretimes when you cannot preserve them on site. In other circumstances too, it may be necessary to
dig away the part of the soil layer or the shell layer that contains the relic and take it to thelaboratory for detailed examination. Archaeological relics and structures removed from the site inthese circumstances are often exhibited at museums or other educational institutions.
To remove archaeological relics and other artifacts (fig.12,13), they are usually packed in
rigid polyurethane foam system for internal and external support and taken from the site. There
are presently several types of expanded polyurethane resin
available. Two inactive liquids are mixed and stirred,
activating them to foam and harden, producing an expanded
styrol-like material. This material expands and completely
fills the small and irregular spaces around the object. Using
this material, you can completely package complicated andoddly shaped archaeological relics at the excavation site.
Even after it sets up, this material can be cut easily with aknife.

Fig.12. As for a Wet Organic
objects, liquid nitrogen is applied.

27

6-2. Collecting samples of thin-films of thestratum at archaeological sites
It is important to the sciences of geology, prehistory,archaeology, and soil science to record the stratigraphy.
In Europe, various methods for collecting thin sectionsof the sedimentary layer have long been studied with aview to preserving a profile of the stratum. E.Voigt, in1932 –33, developed a new type of resin to be used forcollecting thin-film samples, from cellulose nitratedissolved in acetone (Firma Gustav Tuth Z4/924). This
resin formed a film quickly, and was flexible and strong.
Later, in 1963, D.E. Dumond developed a method ofusing polyvinyl acetate [Elmer’s Glue-All] to collectthin-film samples of strata. In 1964, a method for using
polybutyl methacrylate resin and toluene (1:10) was
developed by P.H.T. Shore. Then in 1967, a method wasdeveloped by Tokuyama for using 2-acetyl cellulose andthe copolymer of polyvinyl chloride and vinyl acetate,that was used for collecting outcroppings by the lackfilm method in order to examine the microstructure ofstrata and sediment.
6-3. Film removal method for soil layers

Fig.13. The wall, covered withJapanese paper or aluminium foil
and in the cardboard box, areembedded in polyurethane form

In a report of an experiment using this method, he stated that it was possible to use it to collectthin-film samples of volcanic deposits and unset-up sediment like that of quaternary deposits. He
added that this method can also be used for tertiary deposits or Mesozoic or Paleozoic deposits, if
they are porous like sandstone, even if the stratum has hardened to some degree. (Dai-cell LAC-7
and Denka lack #21, and Denka vinyl #1000 were used). In 1977, rubber latex was used as a
backing in Britain, and it proved that it was possible to collect a thin-film sample of the stratum
easily in a humid environment.
At the Nara National Cultural Properties Research Institute, we developed new types of
epoxy and polyurethane resin for collecting thin-film strata samples. These new types of resin
made it possible to collect thin-film samples in a very hard soil and humid environment. Thesematerials were further improved and commercialized as Tomak NR-51 (epoxy resin) and NS-10(polyurethane resin). In addition, isocyanate resin and acrylic resin have been used as surface
treatment agents. The resin is applied to the surface you want to transfer, a backing material is28attached, and then another layer of resin is applied. After the resin has set up completely, the film
is peeled off the stratum. The film is washed with water and surface-treated, and then affixed to apanel for exhibition or storage (fig.14).

Fig. 14. After the stratum is made smooth, the resin is spread. Backing is done by using gauze.
After consolidation, the stratum is peeled off.

29

Finishing stage of preparing the film surface by spraying resin

Film removal result displayed in a museum.
Even heavy materials like potsherds can be fixed onto film

30

Characteristics of Waterlogged Woods

KOHDZUMA Yohsei
Center for Archaeological Operations
National Research Institute for Cultural Properties, Nara
Independent Administrative Institution

1. Introduction
Almost every organic material is a link in a food chain, and will normally be decomposed by fungus orbacteria and eventually disappear. Yet numerous wooden artifacts and pieces of natural wood that arefound from archaeological sites have retained their shapes despite having been in the ground for
centuries. Wooden objects unearthed from archaeological sites are generally referred to as excavatedwood. The reason why excavated wood has survived over the centuries to the present day is not that it
has been in a situation where it was removed from the food chain, but rather that while it was still in
the food chain it was in a special environment where the deterioration process advanced quite slowly.
The site environments where wooden relics are discovered fall into these general categories:
1) Bogs (especially peat bogs)2) Soil where oxygen is cut off by underground water
3) Bottoms of rivers, lakes or seas
4) Glaciers or permafrost5) Deserts
It seems that in these environments, excavated wood retains its form very well over the centuries
because the activity of the decomposers that actively decay wood is largely suppressed. Nevertheless,since deterioration–albeit very slow–has definitely occurred in almost all of the wooden remains
excavated from archaeological sites except those in deserts, some kind of conservation treatment must
be carried out.
Conservation treatments for excavated wood can be traced back to the first use of potassium alumin Denmark in the mid-nineteenth
century. However, after some 80 years
Animals & Plants
had passed, objects treated with thismethod were found to have developed
CO2, H2O, etc.
Organic Materials
serious problems, and potassium alum
has therefore not been used since themiddle of the twentieth century.
Degradation Residues
Thereafter, the defects of the
Figure 1. A food chain

31

potassium alum treatment were overcome as various alternative treatments for excavated wood havecome into use.
This paper outlines what is known at this time about some properties of archaeologicalwaterlogged wood, and then introduces the conservation treatment methods that are now carried out
on excavated wood and other organic materials, including the latest information.

2. Characteristics of Archaeological Waterlogged Wood
2.1 Changes through Deterioration in the Constituent Components of Cell Walls
The cell walls of wood are composed mainly of cellulose, hemicelluloses and lignins. In addition to
those three main components, several percent of ash and extractives are included. Among thosecomponents, cellulose and hemicelluloses are polysaccharides, which are easily decomposed andmetabolized by wood-rot fungi. In the constituent analysis of wood, when lignin is selectively
removed, what is obtained is holocellulose. Holocellulose can be thought of as the total of cellulose
and all hemicelluloses.
Table 1 shows the main constituents of the cell walls of archaeological waterlogged wood. For
simplified comparison purposes, the components have been reduced to holocellulose and lignin.
In recent wood, holocellulose content is about 70% and lignin content is about 30%. In excavatedwood, the holocellulose content drops to about 20% while lignin increases relatively to about 80%.
Holocellulose is the polysaccharide fraction that is easily decomposed by wood-rot fungi. While thewood is buried under the ground, the holocellulose is considerably decomposed and tends to disappear.
In contrast to the polysaccharides, the quantitative decomposition and disappearance of lignin issubstantially less, and as a result its content increases relatively. Although the quantitative decrease is
Table 1. Chemical composition of waterlogged woods
Wood Species

Content, %Cellulose

Hemicelluloses

LigninChemacyparis Obtusa (S. and Z.) Endl.

47.7

21.3

31.0

Pinus densiflora S. and Z. or P. Thunbergii Parl.

11.2

16.0

72.8

Cryptomeria japnica D. Don

40.8

17.8

41.4

Quercus glauca Thunb.

9.8

13.6

76.6

Quercus sessilifolia Blume

10.4

12.2

77.4

Quercus myrsinaefolia Blume

9.5

11.8

78.7

Quercus gilva Blume

10.3

13.0

76.7

Castanopsis cuspidate Schottky var. sieboldii Nakai

11.0

11.9

77.1

Neolitsea sericea (Blume) Koidz.

12.1

11.9

76.0

Vaccinium bracteatum Thunb.

18.3

12.3

69.4

32

small, it is clear that lignin actually decomposes and decreases under the ground. Archaeologicalwaterlogged wood is regarded as wood, but it is actually in a completely different state than recent
wood.
2.2 Increase in Maximum Moisture Content and Reduction in Basic specific gravity
When the structure of waterlogged wood is observed under a microscope, it can be seen to be
surprisingly well preserved. As noted above, regardless of the substantial decomposition anddisappearance of constituents of the cell walls, the structural characteristics are well enough preservedthat the type of wood can be identified. This reflects the fact that components of the cell wall havedecomposed and lost without changing the size of the cell wall itself. New voids have formed in theparts of the cell wall where components have disappeared. Disregarding pieces found in deserts,
glaciers or permafrost, archaeological wood is usually discovered in humid soil. It may therefore be
assumed that the reason that the size of the cell walls does not change is that the new voids opened upby the decomposition and disappearance of constituent of the cell walls are immediately filled bywater.
Maximum moisture content is often used as an indicator of the scale of deterioration ofarchaeological waterlogged wood. The maximum moisture content is the ratio of the weight of water
included in the wood to the wood weight when completely dry (weight of wood substance), expressed
as a percentage.

u=m w − m0× 100
m0

u: maximum moisture content, mw: water saturated weight, m0: weight of wood substanceAs noted above, the constituents of the cell wall decrease along with the deterioration of the wood, andsince water increases by that amount, naturally the maximum moisture content increases. Therefore,
by determining the maximum moisture content of archaeological waterlogged wood, the degree ofdeterioration of the wood can be estimated. To put it simply, the higher the maximum moisture content,
the greater the deterioration. However, since the maximum moisture content generally differs by
species or specimen even for recent wood, in order to gauge the level of deterioration with somedegree of accuracy, it is desirable at the least to compare the figure with the average value for recent
wood of the same species.
Basic specific gravity is the weight of wood substance per cubic centimeter in the state of
maximum swelling.

D=

m0
V

D: basic specific gravity, V: volume of maximum swelling

33

D=

Rδ
δ + 0.01u

R: density of cell wall,

Maximum Swollen Volume of waterlogged Wood

Wood Substancem0 g

Water (mw-m0) g

Degradation

V cm3

Volume： Not Change
Wood Substance： Decrea
Water： Increase※Increase of Maximum Moisture Content※Decrease of Basic Specific Gravity

Figure 2. Degradation of buried woods
3

0.6
Basic Specific Gravity, g/cm

For archaeological waterlogged wood, since thewood substance is reduced even though the outward
size is unchanged, its basic specific gravity may
decrease along with the progress of deterioration(Figure 2).
As basic specific gravity also varies according to
the wood species or the specimen, as with maximum
moisture content, it is desirable at the least to compare
the figure with the average value for recent wood of thesame species.
Maximum moisture content and basic specificgravity vary according to the decrease of constituents,and hence there is a very close relationship between
these two characteristics that is approximately
expressed by the following equation (Figure 3).

0.5
0.4
0.3
0.2
0.1
0
0

500

1000

1500

Maximum Moisture Content, %: density of water

Figure 3.
A relationship between maximum moisture

2.3 Shrinkage through Drying

content and basic specific gravity

Trees grow in thickness as they grow in length, and there is often some degree of difference in thephysical properties of a piece of wood according to the direction of measurement. In wood science,
three basic directions are defined. Such a difference in properties according to direction is calledanisotropy, and the shrinkage of wood through drying is a physical property that shows striking
anisotropy.
Drying archaeological waterlogged wood often leads to drastic shrinkage and deformation(Figure 4). Once such shrinkage and deformation has occurred it is difficult to return the wood to its
previous size and shape even by reimmersion in water. With recent wood, thorough drying does not
result in such extensive shrinkage, and reimmersion in water will restore it to almost the original size.
The degree of shrinking in wood is expressed as the shrinkage. When a wet wood is shrank by
Figure 4. Deformation of anarcheological waterlogged wood

Before drying
34

After drying

drying, the shrinkage of the wood is the ratio of thedimensional change to the original dimensions,expressed as a percentage. The shrinkage when woodis dried completely from a state of maximum swellingis called the maximum shrinkage.

S=

Lw − L0× 100
Lw

S: maximum shrinkage, Lw: maximum length, L0:
oven-drying length

Figure 5. Deformation of cell walls

shrinkage of buried woods

35

Volumetric Shrinkage, %Void Ratio, %The anisotropy of wood shrinking tends to follow the approximate ratio of 1 for longitudinal
shrinkage to 5 for radial shrinkage to 10 for tangential shrinkage. Since water soaks into
archaeological waterlogged wood in an amount equal to the disappearance of constituent componentsof the cell walls, archaeological waterlogged wood shrinks drastically with drying. While tangential
shrinkage amounts to 7~8% in recent wood, in archaeological waterlogged wood it often exceeds 60%.
In other words, a 10 cm object shrinks to about 4 cm. The more deteriorated the object, the greater theshrinkage. Shrinkage anisotropy in archaeological waterlogged wood is most pronounced in thetangential, then in the radial, then in the longitudinal direction. In recent wood the order is the same,but the ratios are not necessarily the same.
For wood in general, shrinkage occurs in the range of moisture content below 30%, which is thefiber saturation point. When archaeological waterlogged wood is dried, shrinking and deformation
begin to occur over a much higher range of moisture content. That shrinking and deformation does not
result from water escaping from the cell walls, but rather from the evaporation of water from lumina
and other macro-spaces. Water is a liquid with very high surface tension. When a liquid with such highsurface tension starts to evaporate via one of the extremely small pits that connect one cell to another,
the interior of the cell is decompressed and a strong attractive force is generated. This tends to attract
an influx of outside air to the interior of
the cell, but that influx is blocked by the100
100
surface tension of the water that is in the80
80pit, causing the cell to buckle and deform
60
60
along with the reduction in water (Figure
40405). This phenomenon is known as collapse.
20
20
Hence in archaeological waterlogged00wood, the fact that shrinking and
0
500
1000
1500
deformation occurs in a range of moisture
Maximum Moisture Content, %content that is much higher than the fiber
saturation point may be regarded as being Figure 6. Changes of void ratio and volumetriccaused by the cell wall having lost the strength to bear the surface tension generated by theevaporation of water.
The fragility of the cell walls results from decomposition and leaching of components of the cellwall structure, and also depends on the increase in the voids inside the wood. Consequently theshrinkage due to drying of a piece of excavated wood may be expected to escalate suddenly at the
point where the amount of air space inside the wood increases to a certain level. In Figure 6, theoverall porosity and the maximum volumetric shrinkage are plotted against the maximum moisture
content or a wood sample. This shows that the overall void ratio increases sharply in the range of the
maximum moisture content. Meanwhile, assuming that the fiber saturation point is unaffected by the
degree of deterioration and remains virtually unchanged at 0.3, the temporary void ratio will gradually
decrease.
That indicates that as recovery occurs through moisture absorption and the amount of temporary
void decreases, collapse will be caused and the amount of permanent void will rapidly increase. The
rise of the maximum moisture content to the 200% level indicates a maximum bulk shrinkage that
follows the line of the temporary void ratio. In this range, rather than being associated with thecollapse of permanent void, the shrinkage from drying appears to depend rather closely on theblockage of temporary void due to desorption of moisture. If similar correlations can be derived formany kinds of wood, the data may well be useful in the selection of appropriate methods ofconservation treatment.

3. Methods of Conservation Treatment
This section describes the treatment methods that are in current use, in keeping with the principles
outlined in the previous section for the preservative treatment of organic materials.
3.1 Polyethylene Glycol Impregnation
The highly reliable PEG method is one of the best treatment methods using water-soluble
impregnation agents. The PEG method was pioneered in the late 1960s and early 1970s by Broson andChristensen of the National Museum of Denmark with the Skuldelev Viking ships, and by Barkman
with the Wasa warship in Sweden. For small objects an impregnation tank is used to perform thetreatment, while for the huge ships which could not feasibly be placed in tanks, a PEG solution was
sprayed onto the wood. In Japan PEG was first used to treat tablets discovered at the Gokuraku-bo of
the Gango-ji temple in Nara, and the first treatment with the currently used heatable stainless-steel
impregnation tanks, in 1972, was for dam parts excavated from the Kodera site in Matsuyama.
PEG is a polymer with the following formula:
HO(CH2CH2O)nH
where n is the number of repetitions inside the parentheses, i.e. the degree of polymerization

36

The properties vary with the molecular weight. PEG 4000S, with a mean molecular weight ofabout 3300, is used for conservation treatment of wet organic archaeological materials. A solid at
ordinary temperature, PEG 4000S is easily soluble in water and an aqueous solution of about 50% canbe produced at room temperature. It melts when heated to 60°C and becomes entirely liquid.
The PEG impregnation treatment begins by immersing the artifact in a low-concentration 20%
solution. Then the concentration is gradually stepped up along a predetermined gradient. During thetreatment, the PEG concentration and the condition of the artifact must be monitored. With some
objects and some kinds of wood, drastic shrinking and warping may begin as soon as a certain
concentration is reached. This results from too high a concentration gradient inside and outside thewood, and is actually due not to PEG diffusion into the wood, but rather to dehydration of the wood
occurring on a priority basis, similar to the phenomenon of natural drying. To preserve the shape when
this happens, the PEG concentration must be temporarily lowered and then raised very slowly, and insome cases it is better to switch to the freeze-drying method described below. Care must also be takenwith respect to acidity, as PEG will break down in acidic conditions even though it is a stable polymer.
Organic objects are penetrated by a variety of elements while they are buried underground, and manyof them are acidic when excavated. As heating accelerates PEG decomposition, the pH level of thesolution must be monitored during the treatment.

A r c hae o lo g ic al
Wat e r lo g g e d Wo o d sOrganic Solvent

Impregnation of water soluble agents Impregnation of water insoluble agents

Solidification or
Crystallization

DryingChemical Reaction

NaturalFreeze-Drying
Supercritical Fluid

Fig.7 Schematic diagram of conservation treatments of archaeological waterlogged woods

37

Impregnation is usually performed up to nearly 100% PEG concentration. But with coniferous
wood that is in a good state of preservation, it is sometimes advisable to remove the object from thetank when 80% concentration is reached and allow it to dry naturally.
The ease of performance and the safety and stability of the chemical make PEG impregnation ahighly reliable treatment method. Yet there are some problematic aspects: the treated object takes on adarker “wet” coloring, and penetration or diffusion may be difficult due to the high average molecularweight (3300) and large molecular size of PEG. Cleaning away PEG on the surface, using alcohol thathas been warmed in a hot-water bath, can substantially brighten the darkened surface. Objects forwhich penetration is difficult have been successfully treated with a two-stage impregnation method
using PEG with different molecular weights, and by adding a surfactant to the aqueous PEG solution.
The two-stage treatment consists of impregnation first with a solution of PEG 400, which has a low
molecular weight and will penetrate spaces the heavier chemical cannot enter, and then with a solutionof PEG 4000S. There is a risk of PEG elution from the treated artifact if it is placed in anenvironment where the relative humidity exceeds 85%, because PEG itself has high affinity with water.
Hence it is best to store treated artifacts in a stable, low-humidity environment.
3.2 Sugar Alcohol Impregnation
To overcome problems in the conservation treatment of wooden artifacts using PEG and sucrose, andto identify an alternative material for treatment, Morgos of the Hungarian National Museum andImazu of the Kashihara Archaeological Institute have conducted experiments with sugar alcohol
impregnation since the late 1980s. Imazu et al found that lactitol was an outstanding candidate due toits effectiveness in conserving organic artifacts and its low molecular weight, resistance to rotting,stability under heat, high solubility, low hygroscopicity, limited discoloring effect and reasonable cost.
After experimental treatments, lactitol was put into use for conservation.
The impregnation process for lactitol is almost the same as that for PEG. The difference is that
whereas PEG melts at 60°C and thus can be added to a solution that is kept at that temperature,powdered lactitol can be added to a vessel heated to 60~80° only up to a concentration of about 70%,
after which the concentration can be increased to a maximum of about 90% by means of gradualevaporation of water from the solution.
It is in the drying and hardening phases that lactitol treatment differs significantly from PEG
treatment. After removing a PEG-treated artifact from the treatment solution and washing the surface
with water, it is cooled in order to harden the PEG inside it, but cooling alone is not sufficient toharden the lactitol solution inside an artifact. To promote crystallization of lactitol, the surface of theobject must be covered with lactitol powder which will serve as crystal nuclei. Also, because there are
four kinds of lactitol crystals which have different coordinate numbers for water of hydration,
monohydrates must be produced in sufficient quantity to ensure good crystal formation. For thispurpose, after covering the surface with lactitol monohydrate, the object is dried by keeping it at atemperature of at least 50°C.

38

The lactitol impregnation method has many advantages as noted above, and the treatment has
been applied in a growing number of cases. Yet problems remain: sometimes the impregnation density
is low, and cracking may be caused by the formation of trihydrates due to non-uniform crystallization
during the drying process. Further development work is needed.
3.3 Higher Alcohol Treatment
The greatest concern in the conservation treatment of excavated wood is the long time period requiredfor chemical impregnation. One way to shorten the time required for penetration of the chemical into
the excavated wood is to lower the molecular weight, i.e. the molecular size, of the chemical. Amongwater-soluble impregnation agents, as noted above, sucrose and sugar alcohol are the leading
treatment agents. On the other hand, non-water-soluble solvents and resins may also be used, and atreatment method using higher alcohol, which has a low molecular weight, is under development.
Higher alcohol is the term used for any alcohol with more than six carbon atoms. Higher alcoholsthat are used for conservation treatment of archaeological waterlogged wooden artifacts include
stearyl alcohol (molecular weight of about 242) and cetyl alcohol (molecular weight of about 270). In
contrast to methyl alcohol and ethyl alcohol that mix well with water, stearyl alcohol and cetyl alcohol
are insoluble in water. They will melt to liquid form when heated to about 60°C.
The procedure for treatment with higher alcohol is to first substitute methyl alcohol for the waterin the wooden artifact, then immerse it in a methyl alcohol solution containing 20% higher alcohol,and gradually raise the concentration of higher alcohol.
One advantage of this method is the short amount of time required for dehydration andsubstitution with methyl alcohol followed by impregnation with higher alcohol. Another is that since
the higher alcohol itself is not hygroscopic, there is no need to worry about elution of the chemical
after treatment even if the object is placed in a humid environment.
Fatty acid ester is another non-water-soluble agent with which treatments are being performed on
an experimental basis.
3.4 Freeze Drying
Freeze drying methods are another means of drying and stabilizing the treatment chemical. In thefreeze drying treatment, after the sublimated vapor is removed, further sublimation is brought about by
one of two techniques, vacuum freeze drying or freeze drying at normal pressure.
To enhance the efficiency of the freeze-drying treatment, a pretreatment is performed which
temporarily replaces the water contained in the wooden object with tert-butyl alcohol. When the
pretreatment is added, there is a definite brightening in the color of the freeze-dried wooden object.
For that reason this technique is often used for the conservation treatment of wooden tablets (narrowtablets used for official records in seventh and eighth-century Japan).

39For coniferous wood in a relatively good state of preservation, PEG impregnation is notcontinued to the normal 100% concentration but is halted at a level between 60 and 80%, after whichfreeze drying is performed.
Experiments are under way in the application of high-vacuum freeze drying to very large wooden
artifacts. There are three kinds of wood that are especially difficult to treat: camphor, chestnut, and oak.
Large artifacts made from these kinds of wood tend to twist and crack in the course of a normal PEG
treatment. As it is impractical to prepare a heatable treatment tank that can accommodate a very large
wooden artifact, the impregnation treatment for such an object must be performed at room temperature.
It has been found that such large artifacts hold their shapes remarkably well when pretreated at room
temperature with a mixture of tert-butyl alcohol, water and PEG, and then dried in a large facility
using the high-vacuum freeze-drying method.

4. Conclusion
Conservation treatment of wet organic archaeological objects has been performed with the main goalof drying them without shrinkage or deformation so they are suitable for display and can withstandstorage. Yet the purpose of conserving cultural assets is not limited to shape retention. It is vital tokeep in mind that in addition to information that can be grasped visually, there are other kinds ofinformation hidden within a cultural asset.
This paper has surveyed the conservation treatment methods that are currently used for organic
artifacts, and for archaeological waterlogged wood in particular. Further study and development isrequired in the field of conservation treatment of organic artifacts, which includes the preliminary
examination of artifacts to determine their levels of deterioration.

40

Recording Methods on Ruins and Relics
NISHIMURA Yasushi
Cultural Heritage Protection Cooperation Office,Asia /Pacific Cultural Centre for UNESCO (ACCU)

1. Subject - All the things to be recognized as cultural properties
1-1. Archaeological sites, features and remains
1-2. Buildings on the ground made of wood, stone, etc.

2. Purposes of record - Record in the form of numerical data and drawings
2-1. Keep the records
2-2. Communicate the information to a third party as objective data
2-3. Utilize them as research materials (data)

3. Methods of record
3-1. Types of method to communicate to a third party
3-2. Measurement
3-3. PhotographThree Elements

3-4. Description

4. Basis of measurement- Determine the position based on the specific criteria
4-1. Three basic elements: distance, direction,height (x, y, z=h)4-2. Determine the position
4-2-1. Relative position(position determined locally)
4-2-2. Absolute position (position on the earth)41

5. Methods to record the position- The datum point for making records and methods
5-1. Plane position
5-1-1. Record by latitude and longitude
5-1-2. Record by Rectangular Plane Coordinate System

5-2. Height
5-2-1. Make sea level the standard

6. Data of datum point
6-1. Distribution map of control points
6-2. Description of control point
6-3. Results

7. Practice of measurement
7-1. Distance survey
7-1-1. Direct survey of distancea) Foot paceb) Tape measure (plastic, steel)c) Invar measured) Electric Distance Meter (EDM)

Balance Weight

Thermometer

7-1-2. Indirect survey of distancea) Optical rangefinderb) Stadia surveyingc) Triangular surveyingd) Trilatelation(Law of Sine-Cosine and Formula of Heron)7-2. Angle survey
7-2-1. Equipmentsa) Transit, Theodolite, Total station42

7-2-2. Methods of surveya) Set of angle measurementb) Repetition Angle Method
7-3. Traversing - Determine the position by combining thesurveys of angle and distance
7-3-1. Connected Traverse
7-3-2. Closed Traverse
7-3-3. Calculation of latitude and longitude distance

7-4. Height survey (Leveling)
7-4-1. Equipmentsa) Tilting levelb) Self-compensating level, automatic levelc) Extensible staff (rod)d) Foot plate

7-4-2. Method of survey - Center leveling is required.
a) Connectedb) Closed
7-5. Survey of details
7-5-1. Plane Table survey
7-5-2. Actual survey(manual survey)
7-5-3. Laser scanning survey

8. Photogrammetry
Survey based on the recording media, photographs. It includes the technique of the Photo-Interpretation.
Photographs are instantaneous records at the moment taken.
8-1. Principlea) Use a pair of photographs.

43b) A target should be included in thephotograph to restore the original
situation when it was taken.
c) Draw a plan by a plotterd) Analog plotter and analytic plottere) Scale of plans and scale ofphotographs
Photographs in a larger scale are
required for drawing plans in a larger scale.
When an analytic plotter is used, theplot scale becomes variable.
8-2. Photographya) Aerial (vertical ) photographyb) Terrestrial (Ground) photography

9. Global Positioning System (GPS)- Method to determine the position by receiving
radio waves from the satellite
9-1. Principle
24 artificial satellites
9-2. Method of surveya) Independent surveyb) GPS survey
9-3. Possibilities of applicationa) Datum point surveyb) Survey of details

4410. 3-D Laser scanning survey- Utilize a laser beam
10-1. Device
Receive the reflection of alaser beam as three
dimensional dataa) Three types for short to long
distance

Can be applied for survey ofarchaeologicalremains

like

Leica Cyrax2500

Leagle LMS-Z210

potteries, buildings and drawing of maps for general use.
10-2. Calculate and draw the plans by using computers

Measuring survey by Short Range 3-D Laser Scanner45

Stone Wall Measurement by Laser Scanner

Result: Dot Image ( 3-D )Draft Drawing ( 2-D )Final Drawing

46

Archaeological Prospection
NISHIMURA Yasushi
Cultural Heritage Protection Cooperation Office,Asia /Pacific Cultural Centre for UNESCO (ACCU Nara Office)1. Introduction
The nondestructive methods of searching from above the ground for artifacts and features
buried below, without making any changes to the ground surface itself. Recently, however,this field is coming to be thought of more broadly as ‘cultural properties prospection’,including not only the study of subsurface features, but also the diagnosis of the internal
structure of above-ground wood or stone edifices. Additionally, the method of analyzing soil,
in order to learn the nature of a feature after it has been uncovered through excavation,
might be called ‘chemical prospection’ . If a pit has been detected, for example, but its
nature is not well understood, the method of identifying whether it is a rubbish pit, amortuary feature, or a simple depression in the soil through chemical analysis could also becalled a form of prospection, according to the perspective currently being advanced.

2. General principles
Archaeological prospection assumes that subterranean conditions, namely differences in thesoil and the presence of foreign objects, may be elicited through differences in some kind ofphysical property. The ground surface might, for example, be pounded with a hammer; as
an acoustic pulse travels faster through hard strata, but more slowly through soft ones, it
may be possible to distinguish between subsurface strata by its speed of transmission alone.
Or when an electric current is applied to the ground, it does not conduct well in dry soil. In
other words, the electrical resistivity is high. But in damp soil the current conducts well andthe resistivity is low. Such phenomena make it possible to differentiate between soil strata
and to detect foreign objects in the soil, based on differences in electrical resistivity.
In this manner, with regards to subterranean features alone, it is possible todifferentiate between soils, and to detect objects of an alien nature, based on a variety of
their physical properties. Archaeological prospection is a nondestructive means of probing
for artifacts and features from above ground, by searching out the sizes, shapes, and extents
of differences detectable to the physical sciences.
Generally speaking, when trying to infer the existence of foreign objects or differencesin the soil, efforts are made to emphasize the data so that anomalies, thought to show
artifacts and features, are rendered more readily understandable. This processsimultaneously amplifies noise, however, requiring care in the actual treatment of the data.

47

Also, in investigations of limited geographical extent, it becomes impossible to distinguishbetween those portions of the data representing the average ground conditions for thelocation, and those that are anomalous. For this reason, it is desirable to measure the widest
area possible.
It goes without saying that archaeological geophysical prospection differs from generalprospection for ground water or mineral resources. One aspect of this difference is thatprospection for underground resources normally involves the probing of considerable depths(many tens of metres). If such methods of measurement and analysis are applied directly tothe shallower depths of interest in archaeological prospection (often less than one or two
metres), the results will be insufficient. From the perspective of these deeper geologicalinvestigations, the regions of archaeological interest fall within the range of noise
associated with the Earth’s crust.
Of great importance for understanding the results of prospection, since it is being
conducted for archaeological sites and artifacts, is the need to refer to the results of previous
investigations of the site in question and the immediate environs. It is necessary to consult
sufficiently with the archaeologists investigating the site in question. When a geophysicalanomaly is detected, if previous archaeological findings for that site and those of thesurrounding area are taken into consideration, this should enhance understanding of what is
causing the anomaly.
If the site and surrounding are totally unknown archaeologically, and moreover there isno general information about the site, it may be possible nevertheless to distinguish between
different soils on the basis of some inherent property, and to determine the extent of suchdifferences. But in such an area it is not possible to link the results of prospection withparticular types of artifacts or features. If prospection is conducted at a location where noteven a distribution survey has been undertaken, and where no record exists of the recovery
of artifacts, the prospection results will be of little validity.

3. Earth resistance surveys
This method consists of passing an electric current throughthe ground, and then inferring the presence of artifacts andfeatures from differences in electric resistivity produced bydifferent soils or by foreign objects. There are manymethods, using different configurations of electrodes, formeasuring resistance to an electric current flowing throughthe ground. These include the Wenner, Double Dipole,
Schlumberger, twin electrode configurations, and so forth (1) .
The basis of measurement for these configurations is the useof four electrodes, two for the current (‘C’) and two formeasuring the potential difference (‘P’).
The difference between the various electrode configurations is one of measurement

3-D Domain for measurement48

Probe Array Configuration
sensitivity. Double Dipole is the most sensitive,
followed by Schlumberger, Wenner, and then twinelectrode (2) . Of these, the Double Dipole and
Schlumberger configurations are seldom used forarchaeology. This is because variations in the contact
resistance, between the electrodes and the soil in which
they are inserted, greatly affect the resulting
measurements(3) . When using these configurations on
poorly conducting ground, salt water is often poured at
the points of contact in order to obtain sufficient
conductivity between the electrodes and the soil.
Another reason why these configurations are not used archaeologically may be because they
are greatly affected by differences in surface topography (4) , making the results difficult tointerpret.
In archaeological prospection, use of the Wenner and twin electrode configurations iscommon. This appears to be because, unlike geological prospection which aims at
producing a pseudo-section (i.e., a vertical cross-section), and takes measurements with alarge number of fixed electrodes, in order to obtain information showing the sizes andshapes of features extending over a horizontal area, archaeological prospection uses amethod in which the electrodes have to be moved between each measurement. Even though
the contact resistance changes slightly with each measurement as the electrodes are moved,since the modern instrument impedance is high the effect on the measurement is not great(3) .
Another reason why these configurations are commonly used is the commercial availabilityof such equipment adapted for these methods.
Multipurpose Resistivity Meter
andRM15 Resistance Meter

3-1. Survey equipment
Equipment employed in archaeological prospection
includes all-purpose instruments used for generalized
surveying, and those developed especially forarchaeological applications. Generally speaking, allpurpose instruments must be capable of greatly increasing
the electric current, when prospecting in deep strata, forwhich the electrodes must be spread widely apart. These
instruments therefore have the benefit of being able toincrease the signal/noise ratio by elevating the current.
Since they are capable of high-voltage electric output(currents of 20 mA or greater), caution must be exercised
to prevent harmful effects to the operator, and carelesscontact with the electrodes should be avoided. Because it
is not possible to use these instrument in a portablefashion, the power unit location is fixed, and wires are run49

to the electrodes. In geological prospection, the electrodes are not moved for eachmeasurement once they have been initially set. Accordingly, this method is used mainly inarchaeological prospection when the objective is to produce a vertical “pseudo-section”.
The RM15 Resistance Meter (Geoscan Research, England), is an example of equipment
widely used in archaeological prospection. Designed for use mainly with the twin electrodeconfiguration, the instrument is mounted on a portable rectangular frame, with the two
mobile probes (C1 , P 1 ) fixed to the bottom of the frame. The remote probes (C 2 , P 2 ), set at a
position sufficiently removed so that the flow between the current probes (C 1 , C 2 ) is radial,
are connected to the instrument by wires. When the electrodes are pushed into the ground ateach measurement position, data are automatically recorded and saved on a mobile datalogger. The system is one permitting very speedy measurement - typically ~0.7 hectares per
day with experienced operators in suitable locations.
The mobile probes on the frame sold with the RM4, a prototype of this model, were
fixed at an interval of 0.5 m, but with the RM15 the probe interval can be selected from 0.5,
0.75, 1.0, 1.25, and 1.5 m. Also, using several of these intervals, it is possible to takemeasurements for a pseudo-section.
3-2. Survey methods
Survey methods can be divided into two types. One aims to produce a pseudo-section as avertical profile, the other seeks to find the horizontal distribution of electrical resistancevariations. If the mobile probe interval is widened in earth resistance prospection, it ispossible to obtain information from deeper strata in the soil. In three-dimensional terms,
each measurement roughly represents the average electrical resistivity of a hemisphericalvolume in the soil. If the probe interval is widened, proportionately greater volumes of soil
are averaged, but small objects become difficult to detect. From experience, the greater
portion of the information is obtained from a depth up to half the probe interval; if the latteris 1 m, for example, the readings typically reflect conditions down to 0.5 m in depth.
3-3. Vertical profiling
By traversing a single line several
times, and increasing the electrodeinterval on each traverse, followedby displaying the results as a seriesof rows laid next to each other (withthe smaller intervals toward the top),
the result has the appearance of avertical profile cut through the soil. This is referred to as an apparent or pseudo-section (5) .
While research on analytical techniques for converting this approximate section into a true
section has been underway for some time (6) , it is still a matter of trial and error, and an
appropriate method has yet to be developed. It is particularly difficult to analyze the soils
lying underneath a stratum of high electrical resistivity near the surface.
50

3-4 Horizontal surveying

Horizontal Map: A burial mound

Surveys made over a horizontal area
are more common in archaeologicalprospection than those made to obtain
vertical profiles. This is because thepurpose of prospection is more often
to determine the location of artifacts
and features, by observing the
distribution of electrical resistance,
and attempting to infer the nature ofanomalies from their shapes, sizes,
positions, and relative strengths.
In
this
type
of
survey,measurements are often displayed as
maps
showingthehorizontal
distribution of earth resistance, withcollected data often averaged bydedicated software over a number ofadjacent measurement points. In otherwords, the value for any point is
replaced with the average of its own
measured value plus those of the fournearest measurement points. Since this is the smallest area for which averaged values can becalculated, the use of this method is common. This is because there may be anomalies in theprocess of taking any individual measurement, or discrepancies in the actual measurement
interval; making the averaged area small is intended to minimize the resulting disparities.
If vertical profiling as described above is conducted over a large number of parallellines, it is possible to obtain results similar to those from a horizontal survey (7) . These data
may first be processed to approximate a series of true vertical sections, and then it ispossible to compile a horizontal plan for specific depths. This is similar to the time slice
technique used with ground-penetrating radar data. Further, it becomes possible to produce
three-dimensional renderings which approximate the particular object under study, using
only resistivity data (8) . Research aimed at developing this type of three-dimensional
resistivity representation is likely to advance in the near future.

51

Image of Magnetic Survey

4. Magnetometer surveys
This method infers the presence ofsubterranean artifacts and features bymeasuring magnetic fields. If there is adifference in magnetism between a featureand the surrounding soil, there will also be aslight difference in their effect on the Earth’s
magnetic field, which can be detected bymagnetometer surveys (9) . Iron-oxides (Fe 2 O 3 ,Fe 3 O 4 ) are the most widely-distributed
strongly magnetic substance on the Earth’s
surface.
Apart from searching for features which
may be detected by slight differences inmagnetism, magnetometer surveys have theunique characteristic of being a very powerful
method for the prospection of kilns andhearths which display thermoremanent
magnetism. Even though a hearth may haveturned visibly red as a result of being heated,as the soils making the hearth and thosearound it are essentially the same, it is very
difficult to detect a difference in electricalresistivity. Becauseof thephysicalphenomenon of thermoremanence, in which
the magnetic domains within the feature are
re-aligned by heating, the hearth produces alarge anomaly by greatly distorting the Earth’s magnetic field, which is possible to detectwith magnetometers (10) .
In contrast to other, more active, survey methods, magnetometer surveys consists of apassive measurement of the Earth’s magnetic field, which is a drawback in conducting thesurvey. When railroads, motor vehicles, houses, or other objects containing masses of ironwhich produce magnetic anomalies greater than those of archaeological features, are near
the survey site, the small variations caused by the features are masked by these larger
disturbances, and are impossible to detect. Moving objects such as trains and motor vehicles
are especially disruptive for magnetic survey work. In addition to these human influences,variations in the magnetic field surrounding the Earth also produce disturbances. These
include diurnal changes in the Earth’s magnetic field, as well as those which take place overthe space of hours, and others occurring in a matter of minutes(11) . All these disturbances arelabelled ‘noise’.

524-1 Survey methods and equipment
At present, there are two methods utilized in archaeological magnetic prospection. One
measures the total intensity of the magnetic field, while the other measures its component
on the vertical axis. For measuring total intensity, proton magnetometers are most popular,
but recently cesium magnetometers have also become available. For vertical axis
measurement, the fluxgate gradiometer, developed especially for archaeologicalapplications, has become universal. Because these instruments measure different
components of the Earth’s magnetic field, it is necessary to exercise caution regarding theresults they display.
In a proton magnetometer, it is necessary to excite the protons in heavy water orkerosene enclosed within the sensor, during which time the device must be fixed in place.
This interval is short, only about one second, but this still means that more time is required
for measurement than with fluxgate gradiometers or cesium magnetometers, which provide
constant excitation and make continuous measurements possible.
When making a survey, measures are taken to reduce the effects of noise. For example,
in total intensity surveying with a proton magnetometer, measurements can be madesimultaneously using two sensors attached to the upper and lower portions of a pole
(gradiometer), or using some other arrangement of two measuring devices, one of which
serves as a reference station
while the other is moved frompoint to point over the target area.
In either case, assuming that bothdevices are subject to the samebackground noise, then by taking
the difference between the twovalues, only the effects due toartifacts and features are obtained.
The same method is followed
Survey results (Goshogawara kiln site)
Fuluxgate magnetometer (Left), Proton Magnetometer
when using the newer cesium

53

magnetometers. As noted above, the fluxgate gradiometer was devised specifically forarchaeological prospection. The FM18 and FM36 are two models developed by Geoscan
Research, which have two sensors stacked vertically 50 cm apart, and record the differences
between their readings.
For both proton magnetometers and fluxgate gradiometers using sensors positioned 50
cm apart vertically, the effective depth of reading is about 1.5 m. Any attempt to increase
the sensitivity and collect data from greater depth would require setting the sensors farther
apart. Since these are placed vertically on the same pole, it becomes difficult to maintain avertical orientation while moving, making the arrangement impractical. A tri-axial fluxgate
gradiometer, which measures independently each of the three directional components of themagnetic field, has been developed (12) , but it cannot be said to have been used widely yet.
Analytical methods utilizing the three components independently may be a future
development in this field.

5. Ground-penetrating radar (GPR)
This type of prospection applies the system and methods utilized in general survey work,
such as investigations of buried pipes and underground cavities, and accordingly there is noequipment developed specifically for archaeological research. As applied research in thisarea is rapidly advancing, there is much information which should be given consideration
for archaeological prospection. GPR in archaeology is necessarily connected with thisresearch (13) .

5-1 Principles
If an electromagnetic wave is propagated towards the ground, about 40% of the energy isreflected at the ground surface, but the remainder penetrates into the ground, with a portion
subsequently bouncing back to the surface from any buried interface. If the returning signal

54

is displayed in temporal sequence, indifferent colours or shades on a grey
scale according to its strength, an image
looking very much like a section of thestrata in the ground may be obtained.
Making inferences about subterranean
conditions, namely the presence ofartifacts and features, by observing theseimages is the basis of this method.
The electromagnetic waves utilized
fall within the band known as
microwaves, and the antennae used inarchaeology are nearly all within therange of several tens to several hundredsof Megahertz (MHz). As this band
overlaps the VHF and UHF ranges used
for ordinary television broadcasts, lifting the antenna unduly when surveying in the vicinityof houses may produce noise in their reception. Electromagnetic waves also tend to leak out
from the gap between the antenna and the ground surface. It is accordingly necessary to takeprecautions while surveying, such as maintaining a sufficient distance from dwellings.
The waves travel freely through a medium of uniform density, but if there is adifference between soils, for example, they will reflect or refract at the soil interface, where
different media come together. If radical density differences, such as those offered by metals,
rock, or cavities, are encountered, these will cause strong reflections. Even in cases such as
postholes, where the difference between the soil within the feature and that comprising it is
not great, nonetheless there will be reflections according to the degree of difference, which
may allow detection of the feature.
As the waves reflect most strongly where media ofvery different densities come together, the largest
reflection in GPR is produced between the antenna andthe ground, or where the waves encounter an air and soil
boundary. This is especially pronounced in pulsed radar.
For this reason, any variation produced by shallow soil
differences or the presence of artifacts can be obliterated
by the saturated condition of the signal from the region
immediately below the ground surface. It is advisable tothink that this condition will apply to the first 30 cm or sofrom the surface, a point of caution associated with thismethod of prospection.

Threshold level55

5-2 Instrumental considerations
At present, the most widely-used method compresses the electromagnetic waves into pulses
for transmission and reception. As the compressed wave strikes an object and is reflected byit, resonances are produced, which cause a succession of similar reflections to show below
the object as a characteristic of this method. At a particular soil interface, for example,
because of the reflection occurring there, a pattern of horizontal stripes continues from thatpoint on. The occurrence of this phenomenon can be misinterpreted as a series of thin soil
layers. In extremely large reflections caused by metals or subterranean cavities, theserepetitive reflections continue downward for a considerable extent. In such cases, thedistinctive pattern of reflection enables the inference of the object as being of metal or asimilar material.
A single wave or scan can be displayed in the manner shown in Figure. In displaying
images made from such data as a vertical section, portions of the scan falling within specificranges are assigned different colours or grey scale intensities. The lowermost values ofthese ranges are called the threshold levels.
During actual survey work, these scans are lined up across the display image, and as
the number of scans taken per second varies from several tens to more than a hundred, if theantenna is moved at a pace of about 8 – 10 sec/m, the number of scans representing the datafor 1m ranges from 100 to more than 1,000. Because of this, one characteristic of GPR isthat large amounts of data are obtained in comparison with other prospection methods. In
most other surveys it is normal to take only one measurement over a 50 cm or 1 m interval,
hence GPR is noteworthy as a prospection method which may enable studying subterranean
conditions in great detail (13) .
5-3 Antennae
There are two types of antennae for sending and receiving the pulses. In the combined orunitary antenna arrangement, the same antenna is used for transmission and reception,
while the split or dual arrangement uses separate
antennae for sending and receiving signals. With the
split arrangement it is possible to combine the twoantennae into a single bundle. Where a gap separates
the two in a split arrangement, an angle is produced in
the signal path which may be better suited to detecting
certain objects, but the vertical path travelled by thesignal going upwards and downwards in the unitaryarrangement provides more potential for detecting an
object in detail. Perhaps because only one antenna isused for sending and receiving, frequencies are
generally lower in the unitary arrangement. In fact, it isdifficult to distinguish between the results of the two
Different display from same data
arrangements in actual use.
56

Methods for moving the antenna over the survey area include pulling a unit fitted withwheels, dragging one mounted on a sled, and carrying one by hand. The use of a sled keeps
the unit in contact with the ground, minimizing energy loss of the pulse. The method ofcarrying an antenna suspended from the shoulders by ropes is used with low frequency
antennae of 70 or even 40 MHz. In low-frequency surveying, the disturbance arising fromthe interval between the antenna and the ground surface does not greatly affect the data.
With the dual arrangement, in which the antennae can be separated by fixing thetransmitter and moving the receiving antenna, it is possible to measure the velocity of thesignal to a particular stratum(14) . The initial and final receiving times for a wave reflectingfrom the top of the stratum can be read from an image recorded over a specific period oftime, and therefore the wave velocity calculated from the distance travelled by the receiving
antenna. The only requirements in this case is information about the distance travelled by
the antenna and the travel times of the waves. In this manner, by having the transmitter andreceiver in separate locations, it is possible to calculate the actual depth of subterranean
features.
5-4 Angle of transmission
The wave radiating from the transmitting antenna is generally taken to be wider than 90°,
although it depends on the frequency. With this wide an angle of transmission, even before
the antenna arrives directly over an object, its presence may be detected from (albeit weak)reflections, travelling diagonally and being displayed on the resulting image. For this reason,
objects such as pipes or even isolated stones may be displayed on the screen before theantenna reaches their actual position, and their images may appear larger than reality. These
images typically describe a parabolic form below the object in the radar image (15) . In a
separate phenomenon, a V-shaped ditch may be displayed with an inverted V-shaped form
extending downward from its bottom. Also, the edges of ditches or post holes are sometimes
seen to assume sharp angles, with reflections centring upon the edge. This phenomenon,
known as the edge effect, is seen not only in GPR, but also in magnetometer surveys andother methods. For all of the above phenomena, the reflection is not an expression of theactual condition of the soil or features.
5-5 Wave frequency and resolution
The wavelength of the emitted pulse is related to antenna size and frequency. A largeantenna with a low frequency emits a pulse with a long wavelength, whereas that from ahigh-frequency antenna is short. Furthermore, the ability of the antenna to discriminate
objects, or its power of resolution, is related to the wavelength, with longer wavelengths
lacking the ability to detect smaller objects. Generally speaking, antennae used inarchaeological prospection with frequencies around 500 to 900 MHz are called highfrequency, and those of 300 MHz or less called low. This difference in frequency is also
related to the penetrating power of the wave. High frequency antennae are able to survey
only shallow strata, while lower frequencies may work at deeper levels (16) . With high57

frequency antennae of 500 to 700 MHz, it is difficult to survey depths of 1 m in wet paddy
soils as seen in Southeast Asia, but it is possible to obtain data for nearly 2 m with antennaeof 200 to 400 MHz. However, for dry soils such as sand or volcanic ash, it is not difficult toobtain data up to 4 m below the surface with antennae of around 300 MHz. The electric
resistivity of the soil is of some value as a criterion for judging the penetration of the wave.
If the overall resistivity is low, radar prospection at deep levels is not hopeful. Conversely,
if the resistivity is high, then prospects for deeper radar prospection are good. Generally
speaking, if the relative dielectric constant of the soil is around 27, prospection to a depth ofabout 2 m should be possible with a 300 MHz antenna.
5-6 Surveying
GPR equipment consists of an antenna (or antennae) for transmitting and receiving signals,
a control unit which sends the signals to the transmitter, and a device to record data picked
up by the receiver. It is common for the control unit and data recorder to be combined into asingle device. Electric generators and batteries are used as the power source; batteries range
from large items made for automobiles, to specially-designed smaller ones.
The antenna or antennae are connected to the control unit by cables, but caution must
be exercised with these in operation. Since the cables themselves are capable of acting asantennae, they should be kept as far from the receiving antenna as possible. If suchmeasures are not taken during the survey, the cables may produce noise, making it
impossible to obtain good data. Similarly, when surveying with long wavelength antennae
Radar survey result from post-hole building58

(300 or 400 MHz), there is danger of noise from nearby dwellings or other structures. At
these frequencies, the antenna’s reception will be greatly affected when close to structurescontaining steel piping spaced less than 1 m apart, for example. Also, in large-scale surveys,
if an automobile serves as the power source, or the control unit is mounted on an automobile
which follows the antenna, it is conceivable that reflections will be received from themetallic body of the automobile itself.
Ordinarily, the receiving antenna is scanned over the survey area along lines separated
by a set interval. This interval is determined by the size of the object being sought. If theobject is small (e.g., of the order of 50 cm), the space between scan lines must be smaller
than this. But no matter how narrow the interval, if the wavelength is too long for the object
being sought it cannot be detected. Moreover, as discussed above with regard to resolution,
since higher frequency antennae are unable to survey deeper strata, deeply-lying small items
cannot be found. This is true regardless of the method of prospection employed.
Even though the signal radiates over a wide angle, if the object being sought is shallow,
depending upon the scan interval used, it may fall between scan lines, and only a small
portion of it may be detected. Accordingly, there are instances when it is necessary to makethe interval very close. Also, depending on the characteristics of the particular antenna used,
the angle of transmission may be rather narrow, making it possible that even deep lying
objects will not be picked up in detail with wider scan intervals.
Another vital practical aspect of surveying is to run the scans in zigzag fashion, witheach line being measured in the
opposite direction from theprevious one. If a feature such asa ditch presents a symmetric Vshaped or U-shaped section the
direction of the scan will notmatter, but if one side has adifferent angle from the other, it
is likely that the reflection of thesignal will vary between the twosides. If this feature is surveyedfrom both directions, eachdirectional set will obtain adifferent type of data, and bycomparing both sets it may bepossible to learn more accurately
the actual shape. With scanstaken from a single direction only,
there is a risk of losing important
Radar survey result from Dien Ban/Thang Chiem,
data. On the other hand, some
Viet Namlinear features may be detected
Bulletin of the Research Center for Silk Roadology
SILK ROADOLOGY 15, colour page 4, 2003
accurately when the antenna
59makes a traverse perpendicular to the feature, whereas the reflection obtained when the scan
direction is parallel to the object is insufficient. Accordingly, it is ideally preferable to cover
the survey area twice, with one set of scans run at right angles to the other. From limitationsof time, however, this method often cannot be followed. As the next best measure, it is best
to make scans at as fine an interval as possible.
5-7 Displaying the results
As stated above, displaying GPR results in a manner resembling a vertical section is thebasis of this surveying method. A variety of techniques are used for this, such as displaying
in different colours or grey scale values, or showing the outline of the wave trace itself. In
examining such displays, caution must be paid to special patterns of reflection such as
ringing or the edge effects described above. Also, as a characteristic of wave transmission,
the velocity will be slower for wet soils, and faster in dry ones. Accordingly, should there bea feature presenting a straight line in actuality, if the soil above varies locally from drier towetter, the object will be displayed as a curved line because the time of travel to and fromthe object varies with the overlying soil conditions(17) . Generally speaking, no matter what
the topography of the ground surface surveyed, the results will be displayed with the surface
shown as a horizontal line. Accordingly, the topography must be kept in mind wheninterpreting the results. Also, when scans are taken with the antenna run up or down a slope,
the waves are transmitted and received at angles perpendicular to the slope, and it must beborne in mind that the results will differ in nature from those taken along a level surface.
5-8 Compiling a horizontal plan
The technique of making horizontal plans using datataken from apparent profiles, previously mentioned
for resistivity, is widely gaining popularity in GPR.
Data from profiles taken at a set interval are enteredinto a computer, and data for a particular period oftravel time are extracted from each profile andarranged horizontally. This produces a horizontal
plan of the distribution of the reflection, refraction,
and attenuation in wave strength for a particular time
period, and is called a ‘time slice’ (18) . Whentransposing the results of the wave behaviour onto ahorizontal plan, the data must be converted tonumeric values; as large differences between thegreatest and smallest values make computationdifficult, measures are ordinarily taken to reduce theorder of magnitude of this difference.
The reason for producing these horizontal plans
is because the shape and size of an anomaly thus60

observed becomes the basis for making inferences
about the nature of artifacts and features of interest toarchaeology. If supplemental information about thephysical properties of the anomaly in question isavailable, the inference may draw closer to the actual
condition. If GPR shows a feature extending in astraight line, for example, and from the archaeology ofthe surrounding region this is thought to be perhaps aditch or a moat, a road, a rampart, a roofed earthen wall,etc., then it becomes easier to infer the nature of thefeature if the physical properties of the object can bebrought into consideration, such as very low readings
in a resistivity survey, or high signal attenuation in theradar survey. Low resistivity would suggest a featureassociated with wetter soils, such as a ditch or moat;high resistivity would indicate a different sort offeature, such as a stone wall or earthen rampart. However, should a ditch with low
resistivity, or a road with high resistivity be encountered in a GPR survey, if the soil above
such a feature is different, this may cause a strong radar reflection. Accordingly, thereflection provides no way to determine the nature of the feature. But by utilizing the resultsof a resistivity survey over the same area, it is possible to specify certain physical propertiesof a particular locus, and it becomes possible to infer the nature of the feature.
By making a horizontal plan, at times it becomes possible not only to infer the
existence of features, but also to observe historical changes in the strata they occupy. As
shown in Figure for example, in a survey in search of subterranean chamber graves, fromthe stratigraphic positions of graves where the chamber still survives, differences may beinferred in the direction of cultivation and in the boundaries of cultivation. These
differences are thought to be associated with changes over time in land ownership.
In the time slice method, when the intent is to differentiate and display separately
features in overlying layers from different periods, it may not be possible to depict thedesired features adequately unless the proper time slice is selected. At times it is necessary
to proceed in trial-and-error fashion. Also, although data are taken continuously along thelines surveyed, as the interval between lines is ordinarily 50 cm or 1 m, it is necessary tointerpolate for these regions to display the same amount of data along both the vertical andhorizontal axes of the plan. Accordingly, when averaging the data in the interpolations,some definition is lost for the finer details of features, such as the corners of a squarefeature being displayed as rounded. Some method of preventing this effect will be needed in
the future.
5-9 Topographically-modified time slices
As stated above, in GPR profiles the ground surface is normally displayed as a flat horizon.

61

In actual survey work, such as a mound of earth covering a stone burial chamber, the groundsurface rises and falls, yet the structure underneath was built with a level surface as its base.
If the normal time slice procedure is followed, the slices will be made parallel to the groundsurface, and the structure will not be accurately represented. For such cases some means ofmodifying the profile is required, so that they conform with the actual topography prior to
making the slices. It is also possible to use topographically-modified time slice techniques
not just where the surface level varies, but also when the ground surface itself may be flat,but the buried features are on an incline. In this case, the slices need to be taken parallel to areflective layer in the profile images.
In comparison with other prospection methods, GPR is characterized by an abundanceof data. As a tool for archaeological prospection, it is still in need of further research. It
should also be borne in mind that, under certain topographic conditions, it may not be
possible to use an antenna effectively, and that there is also a limit on the depth that can besurveyed.

6. Other prospection methods
While the three methods described above are those most widely used in archaeologicalprospection, other techniques are also employed, including electromagnetic (EM) andseismic methods, and occasionally the microgravity. The following account introduces EM.
6-1 Electromagnetic prospection (EM)If an electric current is passed through acoil this sets up a primary magnetic field,
and when this passes over substancessuch as soil or metals with highconductivity, a secondary magnetic fieldis generated (19) . The EM method ofprospection is performed by observing
the strength of the latter, and the size ofthe secondary field is often expressed inunits of conductance (mho or Siemens),
the inverse of the ohm used for earth resistance measurements. This type of survey cantherefore be used to the same effect as an earth resistance survey, and is thus classed as a
non-contact type of resistivity prospection. As the characteristic of this method is thegeneration of a magnetic field during measurement, it has the drawback that accurate
readings cannot be taken if more powerful magnetic fields or other types of noise interfere.
But as there is no need to set up electrodes, it has the advantage of being easy to perform.
In addition to being utilized for the same purpose as resistivity surveying, EM is often
employed in the detection of metals. Using it in parallel with magnetometer surveys for this62

purpose increases the effectiveness (20) . By surveying the same area with both methods,
should any location show an anomaly in both surveys, this means there is some form of ironobject present. But should an anomaly be detected by EM but not be picked up by themagnetometer, it is likely that some non-ferrous metal is buried at that location.
6-2 Equipment
It is generally agreed that the greater the spacing
between the transmitting and receiving coils, thedeeper the penetration of the survey (3) . Amongequipment utilized archaeologically there aremodels designed for detecting shallow-lying
metals with a spacing of 1 m, and thoseintended for searching out large deep structures
such as ditches and moats, with a coil spacing of
3.6 m. The EM38 produced by the Canadianfirm Geonics is an example of an instrumentwith a 1 m spacing, where the measuring coilcan be used in two modes, one with the coilvertical to the ground surface and the other withit horizontal. The depth of information
detectable in the two modes is 1.5 m for thevertical, and 0.75 for the horizontal position.
Also, by taking data in both modes, it can beused for analyzing the conditions of buried strata.

7. Summary: essential points of geophysical prospection
In archaeological geophysical prospection, since the purpose is to detect the presence ofsubterranean features and artifacts, collecting information on previous site investigations,and historic information on the surrounding region, and making use of these in interpretingthe survey are essential elements of the process. In addition, it is necessary to utilize
different types of survey on the same target area, and to compare the results. The various
geophysical prospection methods reviewed here such as earth resistance, magnetometer,
GPR surveys, and so forth, all detect different physical characteristics of the soil. If any ofthese detect an anomaly, it is highly possible that an artifact or archaeological feature ofsome kind lies buried at that spot. Experience over the past 50 years has shown that thesetechniques, alone or (preferably) in combination, can provide rapid and reliable informationon the location, depth and nature of buried features without the need for excavation. Not
only does this reduce expense in archaeological research but it offers a uniquely powerfultool in the broader area of cultural heritage management.

63

References
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15. Vaughan CJ., Ground-penetrating radar surveys used in archaeological investigations,Geophysics 51, pp. 595-604, 1986
16. Daniels D., Surface Penetrating Radar, Institution of Electrical Engineers: Stevenage, 1996
17. Goodman D., Ground-penetrating radar simulation in engineering and archaeology.
Geophysics 59, pp. 224-232, 1994
18. Goodman D, Nishimura Y and Rogers JD., GPR time slices in archaeological prospection,
Archaeological Prospection 2, pp.85-90, 1995
19. Reynolds JM., An Introduction to Applied and Environmental Geophysics, Wiley, Chichester,1997
20. Tabbagh A., On the comparison between magnetic and electromagnetic prospection methods
for magnetic features detection, Archaeometry 26, pp.171-82, 198464

Temperature and Relative Humidity Environment of the North
Section of Shoso-in Repository

NARUSE Masakazu
Office of the Shoso-in Treasure-House,
Imperial Household Agency

Temperature and relative humidity environment in the Shoso-in repository has drawn
the attention of various researchers interested in the conservation of cultural properties
since the Edo period. Investigations with a self-recording thermo-hygrometer (using abimetal strip and a bundle of human hair) were made between 1949 and 1959 by the
Osaka District Meteorological Observatory. In the last few years we have used dataloggers to record temperature and relative humidity in the north section of therepository and in a storage chest inside that section. This paper presents the results ofmeasurement over a six-week and a one-year period in 1999 and 2000.
At the daily amplitudes of variations, the average ratio of the temperature
variations in the upper story of north section to the outdoors was 14/100 and that in thechest to the outdoors was 13/100, while the average ratios of variations in relative
humidity to the outdoors were 20/100 and 3/100, respectively. At the annual amplitudes
of variations, the ratio of the temperature variation in the upper story of north section to
outdoors was 77/100 and that in the chest to the outdoors was 76/100, while the ratios
of variations in relative humidity to outdoors were 60/100 and 25/100, respectively. The
limited humidity variation inside the chest is due to the buffering properties of wood
used.

65

Temperature and relative
humidity variation from May
20 to June 9, 2000

Temperature and relative
humidity variations from
September 17, 1999 toSeptember 16, 2000

The temperature variations
curves for the lower story
and inside the chest are notshown because they arenearly identical to that for
the upper story. The
relative humidity variation
curve for the lower story is
not shown because it isnearly identical to that for
the upper story.

66

4. Final ReportTraining course on cultural heritage protection in Asia and the pacific
ReportNguyen Kim Dung
Vietnam Institute of Archaeology
National Center for Social Sciences and Humanities
Ha Noi, Viet Nam

The training programme for Cultural Heritage and Archaeological Conservation Science was organised by the
Cultural Heritage Protection Cooperation Office, Asia/Pacific Cultural Centre for UNESCO in Nara, Japan(ACCU), from 2003, July 7th to August 30th. I am a Vietnamese archaeologist and have fortunately been
accepted as a participant of the programme titled: “Training course for Researchers in charge of Cultural
Heritage Protection in Asia and the Pacific”.

The training course was very well organised by ACCU, Nara. It focused on two important
subjects:
Subject A: Cultural Heritage Conservation Science.
Subject B: Archaeological science: Archaeological research and survey methods.
The training course took place at various venues, including the Conservation Science
Laboratory of Nara, the National Research Institute for Cultural Properties (Nabunken), theInstitute of Archaeology in Kashihara (Koshikoken), Nara University, and the ACCU, Nara
Office.
During the training course, field trips to various museums, temples, shrines, archaeologicalsites, as well as conservation laboratories were taken. These field trips provided a valuable
opportunity for the participants to network with experts within this field; this has promoted
mutual understanding and cooperation in our work. Looking back to what I have learnt andwhat I have seen, I could hardly believe that I was able to achieve so much practicalexperiences and professional liaisons in just two months. These will be very useful for mywork and I wish to share my new-gained knowledge and skills with my colleagues. The
subjects covered in this training program were broad and detailed; this report could only serve
as a summary of some of the main topics and what I have learnt in this training course.

67

I. Cultural Heritage Conservation Science
1. Conservation science for archaeological objects:
Archaeological objects are classified into many categories according to their materials and production
techniques. Unearthed archaeological objects could also be scientifically classified by the degree towhich their inorganic and organic components have deteriorated. Artefacts within these classifications
still differ in their type and sources. Conservation science involves the study of excavated objects andtheir treatment methods so that they may be preserved for various purposes such as exhibition andresearch.
Conservation Science as a formal discipline was established in Japan in the early 1970’s; it has
been developed to a high standard in response to the necessity of protecting the cultural heritage inJapan.
Conservation Science is sub-divided into various branches of study:
1. XR (X-Ray Radiography) analysis for metal and wooden archaeological objects.
2. CR (Computed-Radiography) analysis for glass objects.
3. XRF (X – Ray Fluorescence spectroscopy) analysis for metal and glass objects.
4. XRD (X-Ray diffraction) analysis for metal and glass objects.
5. FT-IR (Fourier Transform Infrared spectroscopy) analysis for textile (organic) objects. Thismethod is developed with the use of a Computed Scanner equipment.
6. PEG (Polyethylene Glycol), FD (Freeze drying), Higher alcohol, Lactitol and Trehalose mixture
methods used for the treatment of waterlogged wood.
7. Environment and Zoo archaeology analysis.
8. Dendrochronology.
9. Pottery reconstruction and treatment.
10. Air pollution and its effects on cultural heritage.
11. Conservation treatment used in excavation.

68

Workshops in which the above conservation methods were demonstrated were held by conservation
scientists of the Nabunken, Kashikoken and Nara University. I was able to learn about various
methodologies and conduct practical experiments. Although there was an opportunity to learn about awide range of techniques, due to time constraints in the two-month training course, I wasn’t able tofollow through the experiments daily and observe their outcomes. Conservation science activities
undertaken in other Japanese institutions such as museums, temples and other conservationlaboratories such as the Gangoji Institute, Laboratory of Cultural Properties in Sosho-in and Todaiji
Temple gave me further insight. I observed that high technological instruments were used for
conducting conservation work in many of these institutions and was impressed by the advancedevelopment of conservation science in Japan.

1-1. Conservation of Inorganic archaeological objects(Inorganic objects include bronze, iron, gold, clay, pottery, roof tiles, stone and glass etc.)
Within this subject, I learnt about two key stages in the conservation process:1. Analysis of excavated articles before conservation treatment.
The examination ofarchaeological objects before applying conservation treatment is considered a high priority.

2. Selection and application of appropriate conservation treatments in consideration of thecharacteristics of the artifact. The production technique used and the current condition of an
object are also important considerations in determining the appropriate treatment to apply.

1-2. Analysis of iron objects before conservation treatment
X-ray Radiography is commonly used to analyse objects in the first stage. I practised the various stepsof analysing an iron object before the conservation treatment stage. Being an Archaeologist, I
understand the importance of the analysis process and in this case I was very interested in learning
how to apply scientific technologies usefully. The analytical procedures usually takes a long timesince it is important to gain a thorough understanding of the nature of an artefact before an appropriate
conservation treatment can be determined. In particular, we need to choose a suitable resin solution touse for treatment.
The procedures of analysing iron objects is described below:
1. Take digital photographs to record the original condition of an artefact before
conservation treatment.
2. Use X-ray Radiography to understand an object.
wavelength hard X-rays are used.

In the case of iron objects, short

3. Use stereo X-ray Radiography to study the inner structure of objects.
4. Use X-ray Diffraction to understand their degree of damage and locate cracks, corrosion
etc.. This method is also used to identify the mineral composition of oxidized iron.
5. Use X-ray computed tomography (X-CT) on the object to obtain a three dimensional view
(3D image). From this, we can analyse the distribution and extent of cracks and corrosion
on the surface of objects.
6. Hand-drawings are made as records which are placed on object-cards. In the process ofdrawing and recording, the condition of an object can be better understood.

69

7. Observation using a stereomicroscope to determine the cleaning and conservation
methods to be applied.
8. Initial cleaning of the object by a hard steel tool. More thorough cleaning is achieved byapplying the Brasive method (blowing alumina powder onto the object) or by using agrinder to clean its surface.
9. Desalination of iron objects , ie. extracting chloride ion from the object by using
deoxidized water with an inhibitor under high temperature and pressure .
Within X-ray Radiography, I was introduced to various advanced equipment, including the X-ray
fluorescence analyser and the X- ray diffract meter. These are essential instruments for the analysis of
inorganic objects.
The analysis process may involve a combination of different techniques. For example, a bronze
mirror was analysed by using a digital microscope, X-ray Fluorescence Analyser as well as a
Computed 3-D laser Scanner. The analysis results were remarkable.
Examination of materials by X-ray is preferable as it causes no damage. The chemical
constituents of an artefact can be identified using an X-ray fluorescence analyser. X-ray is fired into asample and the energy emitted is measured. This provides an accurate quantitative analysis of thematerial.
X-ray Radiograph of iron artefacts are examined using a stereomicroscope. The microstructureof cracks and corrosion on the surface of objects can be observed. In our case study, the artefact under
examination also contained damage caused by chloride compounds (salt damage). These were drawn
and recorded in detail based on examining the X-ray photographs. Desalination is commonly achievedby using mechanical methods; a precision grinder or hard steel tool is used to remove corrosion.

1-3. Iron object conservation treatment
After desalination, the iron objects were impregnated byacrylic resin and immersed in a solution (1000ml H2O + 0,2%
Natri Boras BTA + 0,1% Benzotriazole) under hightemperature and high pressure. Benzotriazole treatment isapplied for iron objects that contain chlorides and extensive
corrosion. Acrylic resin Paraloid B-72 is effective for the
consolidation and protection of objects.

2. Conservation of organic archaeological objects(Organic objects include wooden objects, wooden container, wooden tablets, waterlogged wooden
objects, textile, lacquer etc.)2-1. Before conservation treatment
In the case of organic objects, non destructive analytical tools commonly used include fluorescent Xray analysis, X-ray diffraction, and high technology equipment FT-IR. Soft X-ray).
Advance techniques such as the application of stereo X-ray Radiography for wooden objects
were also taught.
X-ray Fluorescence Spectroscope (Three dimensional emission of fluorescent rays) and
Scanning electron microscope or microscopic FT-IR spectroscope is used on textile materials to70

understand the infrared spectra of silk fibres. The gas chromatographic mass spectrometer and theultraviolet absorption spectrum method are also used to identify organic objects. However, samples ofancient textile materials are usually rare, especially those featuring urushi (Japanese lacquer), dye orresin. To solve this problem, according to Prof. Masanori Sato, the FT-IR spectroscope used together
with a scanning electron microscope can provide useful information even from small fibres.

2-2. Conservation Methods for waterlogged wood
This topic was covered at the Nabunken and Kashikoken. I
was engaged in experimental work at both institutions andhave found the various conservation methods applied forwaterlogged wood very interesting. As an archaeologist, I haveoften excavated sites where wooden objects were found, yet I
have had very little experience in treating wood. I cantherefore appreciate the importance of training in thesetechniques. I hope that I can further my knowledge after
reading the numerous reports and publications which were so
generously given to me.
Similar to other conservation procedures, the analyticalstage for the conservation of wooden object is of highimportance. In particular, the characteristics of waterlogged
wooden object must be identified.
Wood is composed mainly of cellulose, hemicelluloses and lignin. In the case of excavatedwood, the content of holocellulose and lignin is 20% and 80% respectively according to Dr. Koezuka.
Compared to recent timber, old wood that has been buried underground has a high content of lignin.
Other constituents have deteriorated while the percentage of water have increased. With this inconsideration, excavated wooden objects must be kept soaked in water.
The following are key considerations when analysing samples of wooden artefacts:
1. Observation of waterlogged wood sample with a microscope.
2. Measuring changes in moisture content.
3. Shrinkage from drying is measured by taking radial and longitudinal measurements. This
helps in understanding the direction in which shrinkage occurs.

4. Choice of conservation technique is dependent on the size, weight, fragmentation and physicalstrength of the wooden object.

2-3. PEG treatment method:
PEG is a type of polymer with the chemical formula HO(CH2CH2O)n H. ‘n’ signifies the degree ofpolymerization.
The PEG 4000S method is often used for treating wet organic materials.
At ordinary temperature, a solid sample of PEG 4000S is soluble in water. At room temperature,
50% solution of PEG is widely used. However, a low concentration of 20% solution is used at the
beginning of the impregnation process. The concentration is then monitored and increased slowly.
When the concentration of the PEG solution has reached 80%, the wooden object is considered
to be well treated for preservation. It is then washed with warm water and left to dry naturally.

71

After applying conservation treatment, the wooden object should be kept in low humidity
conditions.

2-4. Lactitol Conservation method:
Lactitol is a sugar alcohol composed of galactose and glucose units. Trehalose is also a sugar alcohol.
Lactitol with Trehalose can be mixed at a ratio of 9:1. Wood is often immersed in a 1% solution of
EDTA-2Na for 24 hours to help preserve its natural colour.
Summary of experiment:
1. Lactitol ( 50% lactitol+50%water); Trehalose ( 50% trehalose+50% water) were used in thisexperiment.
2. Immerse wood object in tap water for 2 to 3 days.
3. Sugar concentration of the impregnation solution may be increased at room temperature.
4. At the beginning, 30 % lactitol-trehalose solution is used. 0.02% Kathon CG is then added tothe solution. The melting temperature of lactitol-trehalose is 60oC. The sugar concentrationof the solution is gradually increased to up to 65% sugar concentration at room temperatureduring the impregnation process.
5. When the impregnation process has been completed, the drying process can occur at room
temperature, or in an oven at 50°C.
6. The wood is then in water and absorbent paper is used to pat its surface dry. Sometimes, thedrying process is repeated at a temperature of 50°C.
7. The treated wooden object is then kept at room temperature.
Other methods also used in the experiment include freeze drying and treatment using higher
alcohol content solution.

3. Practices observed at excavation sites:
It was particularly interesting to observe the practice ofmaking imprints of the section of an excavation site (itscultural layer). This was done by applying epoxy andpolyurethane resin onto the surface of the soil section. A
backing material such as thin cotton fibre is then attached,
and more resin is applied onto its surface. When the resin
has consolidated, a soil imprint of the section of an
excavation site is achieved. Such imprints of the culturallayer of an excavation site are important as a record of
the result of an excavation, or for exhibition purposes.
Various methods used to extract objects from an
excavation site were also observed. Liquid nitrogenmixed with polyurethane foam was used to remove
organic object from wet soil. Fragile artefacts are
removed by using the synthetic resin casting method.

72

4. Air pollution and its effect on archaeological objects and cultural heritage
An interesting research Air Pollution and its effecton Cultural Properties presented in this training
programme highlighted that there has been much
focus to increase scientific research in the area ofcultural heritage protection. Our cultural heritage isbeing adversely affected by environmental
conditions, such as the changes in humidity andtemperature, acid rain and other pollution. Further
damage is being caused by mould and insects. For
example, numerous stone carvings and tablets havebeen damaged by environmental factors. Bronze
objects are often damaged by acid rain.
Archaeological objects and historical monuments
have deteriorated due to corrosion, discoloration, thepresence of iron sulphate and calcium carbonate etc.
At Nara University, I learnt about the methods
for monitoring air pollution. We prepared 25 filterswith 30% Triethanolamine solution for our
experimental work.
Filters were replaced at various sites. Old filters thatwere collected were analysed by transferring thedigital recording data into a computer. From theseresults, I observed changes in humidity and temperature, and the effect of air pollution on plates ofmetal samples from the site. Analyses of these samples were carried out using an Ion
Chromatography equipment. Results were interpreted using a computer and scanner, which
automatically classified the causes of changes on the metal sample. From these information, scientists
can determine the appropriate actions for cultural property protection at specific sites.

II. Archaeological science: Archaeological research and survey methods
1. Archaeological method and Archaeological survey science
Archaeological research in Japan is highly developed and incorporates the latest technologies.
Advanced survey and excavation equipments, as well as various scientific instruments are used forinvestigation and analytical work. They are very useful tools for conducting archaeological research.
Archaeological excavation procedures in Japan are summarised in the following:
1. Preliminary research to identify the site: Site investigation by photographing and mapping torecord the features and topography of the site; collect soil samples for dating; research thehistory of the site from old drawings and archives.

732. Making an excavation plan: Taking detailed site surveys using geophysical survey methods;
taking original topographical recordings; setting up small test pits to collect and analyse soil
samples; setting up control points for the measuring survey; preparing large-scale maps.
3. Excavation: Firstly, grids are set up on the site. Further measuring surveys are taken by handdrafting, photogrammetry, 3D laser scanning and photographing. Excavation pits are then dug
taking into account the site layers and features identified. Soil samples are taken for pollen
analysis. After excavation, conservation science is applied for the preservation of soft remains,
important soil layers or at times the entire site (such as a burial site) is preserved. The public
is informed about the findings and the historical significance of the site.
4. Post excavation work. Mapping of the archaeological features; Analyses and classification ofunearthed objects, records are taken of artefacts by hand-drawing or photographing. Reports
are published and artefacts are preserved and prepared for exhibition.
5. Preservation of the excavated site if necessary. This may include landscaping work or the
addition of public facilities.
The following is a detailed description of some of the above archaeological procedures:

2. Preliminary Site Identification
Information from maps, photos and other local documents are collected for an archaeological site andfield trips are taken. The surface of the site is examined to obtain further information to determine thenature of the site (ie. Whether it’s a settlement site, burial site or architectural site.) Often aerial
photographs are taken.
Collected samples are analysed for further information such as the historical period to which thesite belongs. Further historical research is undertaken by studying old drawings, ancient archives orby interviewing local residents.
Site distribution maps are printed to educate the public about the location of archaeological sites
and the role of archaeological research. This is done so that the historic importance of a site can beunderstood before the site is used for other purposes. I consider this a very important part of thepreliminary research stage.

2-1. Test pit
Test pits are dug before excavation in order to understand the stratigraph (the cultural layers) of thesite and hence the nature of the artefacts to be found. This information is used to plan large scale
excavations. Traditionally several small pits around 1m3 are dug around the site. The core boring
tube method is used in some cases. However more advanced techniques have been used recently, suchas the Geophysical Survey method. This method will be described in detail later.

2-2. Excavation.
1m2 or larger pits are set up in grids. The size of the pits may vary depending on site characteristics.
Advanced survey methods are now commonly used in Japan. Besides the traditional techniques,Japanese archaeologists use advanced scientific instruments such as EDM (Electromagnetic DistanceMeter), Photogrammetry and 3D laser scanning.

74

2-3. Post excavation work.
In Japan, reports are produced after archaeological excavations. The technology available for creating
photos, drawings, maps, and other documents is very important in this stage. Such archaeologicalreports are produced as records, which could be used for future reference, information sharing, and as
research data. The records take various forms and are produced by various means to suit a range ofuses

3. Survey methods:
I undertook a lesson on basic survey methods to determine the location of a site. There are 3components: distance, direction and height. Absolute position is determined by giving the longitudinaland latitudinal location of the site on earth. Relative position is determined by giving the xycoordinates of the site - this describes the location of the site by its distance (in meters) and direction
from a local datum; this is known as the Rectangular Plane Coordinate System. The height of the site
is measured relative to sea level.
Various measuring techniques and survey equipments were introduced during the course. I also
learnt how to calculate the latitudinal and longitudinal distance of a site, as well as how to take alevelling survey. Archaeologists often use database from topographical research, and usually havehands-on experience with survey instruments. However, I have very limited knowledge in taking
surveys and this training course has given me a valuable insight on the techniques involved.
Photogrammetry, GPS and 3-D Laser scanning are commonly used in Japan for archaeologicalsurveys. I was given basic training in the techniques of Photo-interpretation and its principles, Aerial
photography as well as Terrestrial photogrammetry. From this training, I can appreciate theimportance of scientific technology and its application in Archaeology.

4. Archaeological Prospection
Archaeological Prospection was a very interesting subject taught. Using various techniques,archaeological features and objects buried underground may be detected prior to excavation. The
lectures introduced the principles of archaeological prospection and some of the techniques used:
・Earth resistance survey: this technology is applied in archaeological vertical cross-section
surveying as well as horizontal surveying. Mr. NISHIMURA Yasushi pointed out that inarchaeological survey, the Wenner and Twin electrode configurations method is popularly used.
・Magnetometer surveys. Buried archaeological artefacts or features are detected by measuring
earth magnetic fields.
・ Ground-Penetrating Radar (GPR). This method is useful for taking general surveys, forexample, to investigate buried pipes and underground cavities. I was introduced to the
instruments used for this technique and the ways in which results were presented, such as usinga ‘wave trace’. I also learnt how to compile a horizontal plan (Time Slice) from GPR profile
survey. The lecture also covered Topographically-modified time slices.

75

5. Conclusion
On completion of this training program, a comparison between various conservation andarchaeological methods was possible. I was able to understand the importance of selecting theappropriate method in conservation and archaeological practice. As an archaeologist, such knowledge
and practical experience is essential.

Acknowledgements:
Finally, I wish to express my gratitude in the first place to Mr. USHIKAWA Yoshiyuki, Director ofCultural Heritage Protection Cooperation Office, Asia/Pacific Cultural Centre for UNESCO (ACCU) in
Nara, and to Mr. NISHIMURA Yasushi (ACCU) for their help and teaching. I also owe much thanks to theassistance given by the staff of ACCU, Nara Office, Conservation laboratories, Archaeological Institutes
and Museum. Thanks are also expressed to Dr.KOEZUKA Takayasu, Dr. KOHDZUMA Yohsei, Dr.
SATO Masanori and their assistants at the Nabunken; Dr. IMAZU Setsuo, Dr. HASHIMOTO Hiroyuki, Dr.
KAWAKAMI Yoichi from the Kashihara Institute of Archaeology; Prof. NISHIYAMA Yoichi of Nara
University. This training has been a keystone in advancing work in the field of cultural heritage
conservation, the advanced knowledge that has been gained will be of much use.

76

5. Appendix
5-1. Programme Schedule
5-2. List of Instructors

Nguyen Kim Dung
（Viet Nam）
Training Schedule
July 7th (Mon)
8 (Tue)Arrival in Japan
Introduction to ACCU and Greeting（Nabunken, Kashikoken, Nara Univ., Gangoji）

9 (Wed)＜Conservation Science for Archaeological Remains＞ （Nabunken）

Introduction to Conservation Sciences and Facilities
10 (Thur)

Removal of Fragile Objects from Archaeological Site

11 (Fri)Removal of Fragile Objects from Archaeological Site

12 (Sat)13 (Sun)
14 (Mon)First Aid for Finds

15 (Tue)First Aid for Finds

16 (Wed)

Lacquer Film Method for Soil Layer Removal

17 (Thur)

Lacquer Film Method for Soil Layer Removal

18 (Fri)

Restoration and Preservation of Finds, Keeping and Display(Tobunken, Tokyo National Museum)

19 (Sat)Seminar of Viet Nam Archaeology (Kokugakuin Univ.)

20 (Sun)21 (Mon)National Holiday

22 (Tue)

Conservation Science for Metal Objects

23 (Wed)

Conservation Science for Metal Objects

24 (Thur)Conservation Science for Metal Objects

25 (Fri)

Environmental Archaeology

Wood and Dendrochronology

26 (Sat)27 (Sun)
28 (Mon)Conservation Science for Water-logged Wood

29 (Tue)

Conservation Science for Water-logged Wood

30 (Wed)

Conservation Science for Water-logged Wood

31 (Thur)Planning of Conservation Science Training Course
Details of Conservation Science Training Course and Studyof Training Facilities

August 1st (Fri)
2 (Sat)77

3 (Sun)4 (Mon)＜Conservation Science of the Restoration and Preservation ofArchaeological Remains＞ （Kashikoken）

Introduction to Conservation Sciences and Facilities
5 (Tue)Conservation Science of Excavation Site

6 (Wed)Conservation Science of Burials and Artifacts

7 (Thur)

Restoration and Preservation of Finds

8 (Fri)

Restoration Methods and Materials for Bronze Artifacts

9 (Sat)10 (Sun)
11 (Mon)＜Air Pollution and Cultural Heritage＞ （Nara University）

Introduction to Environmental Science Study
12 (Tue)

Introduction to Environmental Science Study

13 (Wed)Air Pollution and Cultural Heritage Protection

14 (Thur)On Site Observation Method of Air Pollution

15 (Fri)

On Site Observation Method of Air Pollution

16 (Sat)
17 (Sun)18 (Mon)＜Archaeological Survey and Conservation Science＞ （ＡＣＣＵ）

General Introduction of Archaeological Survey Methods
19 (Tue)

Measuring Survey Method

20 (Wed)Archaeological Prospection Method

21 (Thur)

Restoration of Japanese Fine Arts (Kyoto Nat. Museum)

22 (Fri)

Conservation Science, Treatment Method（Gangoji）

23 (Sat)24 (Sun)
25 (Mon)27 (Wed)

Conservation Science of Heirloom Treasures（Shosoin）
Restoration of Japanese Lacquer Fine Arts
(Nara National Museum)Traditional Handcraft in Nara and Restration

28 (Thur)

Draw out of Report to ACCU

29 (Fri)

Submission of Report to ACCU

30 (Sat)

Departure for Viet Nam

26 (Tue)

Schedule had been slightly modified due to weather and excavation site procedure.

78

Lectures

KOEZUKA Takayasu

IMAZU Setsuo

Center for Archaeological Operations,
National Research Institute for Cultural
Properties, Nara
Independent Administrative Institution
9-1, 2 chome Nijyo-cho, Nara-shi 630-8577
Tel. +81-(0)742-30-6847
Fax. +81-(0)742-30-6846
E-Mail: koezukat@nabunken.go.jp

Archaeological Institute of Kashihara,
Information Department, Conservation
Science Laboratory
1 Unebi-cho, Kashihara-shi, Nara pref.
634-0065
Tel. +81-(0)744-24-1101
Fax. +81-(0)744-6747
E-Mail: setsuo.imazu@nifty.com

NARUSE Masakazu

KOHDZUMA Yohsei

Office of the Shoso-in Treasure-House,
Imperial Household Agency
129 Zoshi-cho, Nara-shi 630-8211
Tel. +81-(0)742-26-2811
Fax. +81-(0)742-24-0132
E-Mail: ssi25a@kunaicho.go.jp

Center for Archaeological Operations,
National Research Institute for Cultural
Properties, Nara
Independent Administrative Institution
9-1, 2 chome Nijyo-cho, Nara-shi 630-8577
Tel. +81-(0)742-30-6847
Fax. +81-(0)742-30-6846
E-Mail: kouzumay@nabunken.go.jo

OKA Iwataro
Oka Bokkodo Studio, Kyoto National
Museum, The Conservation Center for
Cultural Properties
527 Chayamachi, Higashiyama-ku,
Kyoto-shi 605-0931
Tel. +81-(0)75-525-2179
Fax. +81-(0)75-252-0233

MATSUI Akira
Center for Archaeological Operations
National Research Institute for Cultural
Properties, Nara
Independent Administrative Institution
9-1, 2 chome Nijyo-cho, Nara-shi 630-8577
Tel. +81-(0)742-30-6851
Fax. +81-(0)742-30-6856
E-Mail: makira@nabunken.go.jp

UEDA Naomi
Gangoji Institute for Research of Cultural
Property
2-14-8, Motomachi, Ikoma-shi 630-0257
Tel. +81-(0)743-74-6419
Fax. +81-(0)743-73-0125
E-Mail: ueda@gangoji.or.jp

MITSUTANI Takumi
Center for Archaeological Operations
National Research Institute for Cultural
Properties, Nara
Independent Administrative Institution
9-1, 2 chome Nijyo-cho, Nara-shi 630-8577
Tel. +81-(0)742-30-6845
Fax. +81-(0)742-30-6856
E-Mail: takumi@nabunken.go.jp

INOKUCHI Yoshiharu
Nara National Museum, Department ofArchaeology
50 Noborioji-cho, Nara-shi 630-8213
Tel. +81-(0)742-22-4462
Fax. +81-(0)742-22-7221
E-Mail: inokuchi@narahaku.go.jp

NISHIYAMA Yoichi
Nara University
The Faculty of Literary, Department of
Study of Cultural Properties
1500 Misasagi-cho, Nara-shi 630-8502
Tel. +81-(0)742-41-9548
Fax. +81-(0)742-41-9548
E-Mail:nisiyama@daibutsu.nara-u.ac.jp79