Europe, researchers and cultural heritage
Civilisations are built up over centuries and millennia. The tangible traces they leave behind enable future generations to find their roots in a shared past. With its historical cities, grandiose remains and more modest historical vestiges, Europe is particularly rich in reminders of our shared history. It is no accident that Europe is the continent for the growing business of art and culture tourism. But this culturally – and economically – valuable heritage is also fragile. It is literally crumbling away, not only from age, but also from the effects of climate, pollution and human negligence.
The meeting of science and technology with art and culture includes the provision of invaluable assistance towards conserving and restoring these riches. Given the necessary resources, researchers can help curators understand the causes, mechanisms and consequences of this deterioration in our cultural heritage. They can develop practices and technologies to control it and offset its harmful effects. For this reason, for the past 20 years or so the European Union has wholeheartedly supported projects focused on these objectives. Over 200 partnerships involving researchers from many different disciplines and origins have helped save a host of such testimonies from destruction. This European approach – working in networks and comparing buildings, materials and objects from different parts of the continent – has advanced research into our heritage and improved its conservation.
Less sulphur, more nitrogen?
One long-time enemy of our architectural heritage is sulphur dioxide (SO2), coming mainly from industrial emissions – even though these have been cleaned up considerably in recent years – and coal-fired domestic heating systems. Increases in automotive traffic has also introduced a range of more complex pollutants, including nitrogen derivatives (dioxide and nitric acid) and ozone. This atmospheric cocktail attacks the surface of materials in different ways depending on their exposure to sunlight, air humidity levels, pH, etc.
|The Parthenon is one of the masterpieces of our global heritage which has been most affected by urban pollution.|
Diagnosis and prevention call for much more sophisticated, multi-factoral analyses and standards than currently exist –the pan-European Multi-Assess project addresses such needs. With the help of sensors placed in various urban areas, researchers are undertaking an extensive campaign to identify and sample toxic components, and to model new "dose-response" functions to combat the corrosion and soiling of different materials by complex combinations of pollutants and atmospheric factors. With participants from 14 countries, Multi-Assess has set out to propose new reference “threshold levels” for implementing the Convention on long-distance cross-frontier atmospheric pollution adopted by the United Nations Economic Commission for Europe, as well as the Union’s own directives in this area.
Multi-Assess (Model for multi-pollutant impact and assessment of threshold levels for cultural heritage)
16 partners – 14 countries (SE-AT-DE-CH-IT-GR-UK-CS-NO-PL-LV-FR-EE-BE)
Started: January 2002 – 40 months
Biomedicine to heal stones
Urban monuments have undergone regular cleaning for several decades, either with chemicals, which can cause environmental problems, or with lasers, a method limited by the danger of physical damage to the materials.
|Detailed microphoto of the marble structure covered in black dust – Freedom Monument, Riga (LT).|
Without pretending to actually look for a substitute for these traditional methods, the six universities and one industrial partner in Biobrush are exploring a non-aggressive alternative approach known as bioremediation. The idea is to identify bacterial micro-organisms that can decompose the mineral and organic deposits encrusted on the stone or brick. Test sites currently include the Tholos Dome at Epidauros (GR), Matera Cathedral (IT) and Riga's Brethren Cemetery (LT).
Biobrush (BIOremediation for Building Restoration of the Urban Stone Heritage in European States)
7 partners (UK-DE-GR-IT-LV)
Started: February 2002 – 36 months
Any curator will tell you that the colours of works of art are as sensitive as flowers to sunlight. The harm caused by lighting is, however, difficult to analyse. This depends on the light source – artificial or natural – and, in the latter case, to a large extent on the state of the sky, the season and the time of day, and on the properties of the light itself. In general, the shorter the wavelength (closer to ultraviolet), the more energetic the photons are and the more aggressive the light. This harmful effect also increases after a certain period of exposure. Sophisticated and reliable measuring and surveillance apparatus already exists, but is expensive and often bulky.
|Evaluating the LightCheck® principle on a tapestry at London’s Victoria and Albert Museum.|
© V&A, London
To fill this gap, five European research teams set to work on the LiDo project, with three of them tackling specifically the problems of conserving works of art. The objective was to design a practical and user-friendly ‘light dosimeter’. The result is the LightCheck® mini-sensor with a photosensitive covering that changes colour, indicating the ‘accumulated’ exposure to light. A spin-off from space technology, it won a European Space Agency award in December 2003.
7 partners (DE-FR-IT-UK-CZ)
The outwardly simple mountain church of Santa Maria Maddalena at Rocca Pietore is decorated with frescoes and houses a very beautiful 16th century carved wooden panel behind the altar. In winter, during church services, a ‘complete’ heating system is switched on and runs continuously for several hours. “This is an enormous waste of energy. The entire building is supposedly heated, but worshippers are cold and the art works suffer from variations in temperature and relative humidity,” explains Dario Camuffo, the Italian climatologist who is coordinating the Friendly Heating project. Santa Maria Maddalena is currently a pilot site where a team of European researchers is testing a radically different heating system – based on common sense. Heating is concentrated uniquely on the space occupied by worshippers. Radiant heat and occasionally forced warm air are provided by low-temperature infra-red sources placed among the pews. An extraction system removes excess moisture from respiration. Over 80% of the heat remains concentrated in the first few metres of the nave, whereas previously 93% of the heated air was dispersed throughout the building.
|The church of Rocca Pietore (IT), a pilot site which is experimenting with new heating systems that are effective, economical and respect the works of art.|
7 partners (IT-BE-FI-NL-PL)
Started: April 2002 – 36 months
Tapestries: analysis without destruction
Heavy but fragile, Europe’s tapestries are sensitive to humidity and light. The Modht project has set out to analyse the condition of certain examples in order to develop conservation methods based on scientific evaluation. But how can we analyse these tapestries without damaging them? “Part of our work consists of producing small model tapestries, using traditional materials and dyeing techniques, then artificially ageing them. What we have discovered is that the dyeing process affects the sturdiness of the object," explains project coordinator David Howell. These models also help define the resistance of the tapestries, the largest of which could take the weight of a double-decker bus.
|Sampling, assessment and testing of a tapestry from Hampton Court (UK).|
Other tiny samples are also taken from the tapestries themselves. Conserved in Belgium, Spain and the United Kingdom, and representative of both northern and southern European schools, these works are all the more interesting to researchers as their history is well documented (original workshop, successive locations, etc.) “Our analyses are already producing very interesting correlations, and the results are due to be presented this July at the University of Southampton’s Textile Conservation Centre,” says David Howells.
MODHT (Monitoring of Damage in Historic Tapestries)
7 partners (UK-ES-BE)
Started: April 2002 – 36 months
Paper’s strange radiation
As it ages, paper gives off a very feeble light which can be captured. This phenomenon, known as chemiluminescence, is not unlike the light given off by glow-worms. It is caused by the ultra-slow oxidation of cellulose – the natural polymer which is the main component in paper – which, at the end of the cycle, results in the irreversible degradation of the medium.
|The operating principle of the prototype chemiluminometer which should enable librarians to assess paper degradation.|
Researchers in the Papylum project have set themselves the goal of developing a prototype hypersensitive chemiluminometer which can both pick up and measure the ‘signal’. This new instrument will enable researchers to explore the complex conditions (temperature, air humidity and pH, ambient light, etc.) which encourage or slow down the paper-ageing process. It will also make it possible to evaluate ways of optimising the conservation of this fragile material. Once developed, it will provide the curators of our main ‘library treasures’ with an easy and direct method of analysing the ‘state of health’ of their documents – as well as taking a series of preservation measures. A prototype chemiluminometer will be presented at Ljubljana in November 2004 (see website).
With the ability to analyse and diagnose other mediums (textiles, resins and paints), this apparatus could have potential uses in totally different research areas, including pharmaceuticals and foods.
5 partners (SI-SK-NL-FR)
Started: July 2001 – 40 months
The evil effects of iron-gall ink
Used throughout the Middle Ages and into the 17th century, in particular by drawers, iron-gall ink continued to be used for manuscripts into the 20th century. But whilst its scriptural or pictorial quality is undisputed, the corrosive properties of its components ‘self-deteriorate’ the works and writings of which it is the lifeblood. “A recent inventory by the Boijmans van Beuningen Museum (NL) shows that more than a quarter of its collection of 17th century Dutch drawings are affected by this phenomenon. The manuscripts of Victor Hugo’s works, conserved in Paris, have seriously deteriorated, as have 60 to 70% of Leonardo da Vinci’s works,” according to Jana Kolar of National & university Library, a coordinator in the InkCor project. “This project has been set up to learn more about this corrosion phenomenon and to establish the best ways of conserving and preserving documents”, Jana Kolar explains. “European co-operation has made it possible to bring together experts from different fields – art historians, curators, physicists and chemists – to tackle the problem.”
|Antioxidising treatment being carried out at the ZfB, in Germany.|
Their research has shown that three parameters come into play in determining the degree of deterioration of the documents: the thickness of the ink layer, that of the paper, and the acidity of the ink. “Once we know these variables, we can foretell the future behaviour of the documents and, where necessary, apply conservation treatments. InkCor's work on degradation mechanisms should also help us to improve certain existing conservation processes.” A patent for an ‘antioxidising treatment’ for commercial use has recently been registered jointly by the ZfB (Zentrum für Bucherhaltung), the National and University Library of Slovenia, and the University of Ljubljana.
8 partners (SI-DE-NL-FR)
Started: March 2002 – 36 months
Battling with salt
Salts erode stone, eat away brick, and encourage mould. The damage can be caused by the crystallisation of the salts in the pores of the material itself, or as a result of a chemical reaction with the components of the mortar. Heritage restorers have to choose between modern industrial products or traditional methods. What are the advantages and disadvantages of these different approaches? When should one be preferred to the other? Are modern-day materials, in particular mortars, compatible with the damaged materials, for example substrates containing salts.
|Venice: salt damage to brickwork and plaster.|
Partners in the European projects Compass and Asset are seeking to understand better the deterioration processes caused by salts, and the technical demands of restoration. In particular, Compass is studying the problems posed by coatings and plasters applied on top of brick masonry (type of damage, causes, quantity of salts, diagnosis, etc.). The ultimate objective is to develop an expert system – an assessment assistant tool – for choosing the most suitable rehabilitation option in individual cases.
Asset is a huge project aiming to validate restoration products and methodologies, based on on-site studies in Zeeland (NL), Venice (IT), La Rochelle (FR) and the Island of Rhodes (EL).
Compass (Compatibility of Plasters and Renders with Salt-loaded Substrates in Historic Buildings)
7 partners (NL-FR-ES-PT)
Started: March 2002 – 36 months
Asset (Assessment of suitable products for the conservative treatments of sea-salt decay)
7 partners (IT-NL-FR)
Started: February 2001 – 36 months
Regenerating marble ‘materials’
Water, heat, atmospheric pollutants and living organisms all ‘prey’ on historic monuments. The complex interactions between the material itself and these various elements produce degradation, the causes of which we still do not completely understand. For years, experts have been using various materials in an attempt to reinforce stone, few of which have proven truly satisfactory. A new and totally different approach is to treat the stone with ‘biological’ BIMS (Bio Inducing Macromolecules Solutions). These provoke the formation of calcium carbonate crystals using technologies inspired by bacterial genetic engineering methods (B. Subtilis and B. Cereus). Two types of stone, bioclastic limestone and Carrara marble, are currently being tested. Bioreinforce’s partners are seeking to develop natural, water-applicable and more user-friendly products.
|Château of Champs-sur-Marne: this early 18th century castle in the Île de France, close to Paris (known to film fans), is one of the sites where BIMS treatments are being tried out.|
Bioreinforce (Biomediated calcite precipitation for monumental stones reinforcement)
7 partners (IT– UK – ES – BE – FR – IL)
Started: February 2001 – 36 months
“With its unique architecture and tones, the organ was a high-technology object well before this concept was invented, combining expert knowledge of the properties of wood and metal with the art of working these two materials. Ingenious remote-control systems are used to operate the mechanisms and bellows,” explains Carl Johan Bergsten, a researcher at GOArt (Göteborg Organ Art Centre) of the University of Göteborg (Sweden) and the enthusiastic coordinator of the Collapse project. Europe's organ landscape presents many common features, but also fascinating differences of construction, style and sound, reflecting the social and economic development of the various regions. All this knowledge and skill are put to the service of music.”
|Organ in the basilica of Santa Maria di Collemaggio in L’Aquila (IT). Built in the second half of the 17th century, this is one of the reference instruments in the Collapse project – 90% of its pipes are corroded.|
Designed by organ builders who signed their instruments with inimitable tones, organs suffer problems of ageing, and certain of their most famous voices have started going hoarse with age. The first case was discovered in 1992 in the famous Stellwagen at the St-Jakobskirche in Lübeck, Germany, the oldest parts of which date back to 1467. Little corrosion holes had appeared in the lead-tin alloy tubes. But the St Jakob’s organ was not the only case of its kind, and it was soon observed that a number of instruments, in many cases from the 15th, 16th and 17thcenturies, were also panting and wheezing. Under GOArt’s baton, the Collapse project was launched in 2002, bringing together the Swedish institute, the parish of St Jakob in Lübeck, a Danish SME specialising in organ building and restoration, chemical researchers from Chalmers University (SE) and archaeometallurgy specialists from the University of Bologna (IT).
“We selected seven organs for reference, all suffering from corrosion, in Italy, Germany and the Netherlands. We also compared them with ‘healthy’ instruments, housed in similar conditions in the same regions. One year into the project we realised that certain of the corroded instruments showed a high and unexpected concentration of acetic acid, a known metal corroder. This acid comes from the wooden parts and gets into the bellows.”
But where exactly does it come from? The acid is found in oak which is used for restoration, although many organs repaired in a traditional way with this material do not demonstrate this problem. Could it be young oak? Could it be that central heating encourages the migration of acetic acid from newly used wood?
These are not the only enigmas posed by these impressive instruments. All the affected organs studied here were built in the German way, with only a very small percentage of tin in their pipes. In the United Kingdom, where tin is mined locally, it can represent up to 20% of the alloy ... and corrosion is almost non-existent. This looks like a serious avenue of investigation, and the Italian researchers' initial results seem to indicate that corrosion is inevitable in alloys containing less than 2% of tin. But specialists are not stopping here and are evaluating the impurities that slip into the metal and could possibly change its microstructure, and once again encourage corrosion.
|One of 1 467 pipes with corrosion holes from the Stellwagen in the St-Jakobskirche in Lübeck, Germany. Magnification of the microstructure of the same element, by the University of Bologna Metallurgy Institute (IT).|
© Ibo Ortgies
Collapse's researchers are not just looking for causes – they also want remedies. Methods for treating corroded pipes and preventing this degradation are currently being studied and tested. At the end of the day, the European partners wish to propose a new vision of organ restoration and maintenance methods. “We hope that the results of this study will be useful in particular in the Central and Eastern European countries with their enormous heritage of around 10 000 instruments," Carl Johan Bergsten concludes.
Collapse (Corrosion of Lead and Lead-Tin Alloys of Organ Pipes in Europe)
5 partners (SE-DE-IT)
Started: 2002 – 36 months