WoodCultHer

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Focused Meeting within the WoodCultHer COST ACTION IE0601, Prague 30-31 March 2009

snapshots from the meetin

 

Consolidation, reinforcement & stabilisation of decorated wooden artefacts

Institute of Chemical Technology in Prague, Czech Republic. 30-31 March 2009 

 

Report

 

Tone M. Olstad, Norwegian Institute for Cultural Heritage Research, Norway 

 & Irena Kucerova, Institute of Chemical Technology, Czech Republic 

 

 

Introduction

The meeting was initiated because there was a need to look into “the state of the art” for the topic: Consolidation, reinforcement & stabilisation of decorated wooden artefacts. The meeting primarily dealt with “non-archaeological”-wood

The outcome of the meeting should give bases and suggestions both for improving present practices, and for clarifying practical research needs on how to consolidate the wood as a carrier for a decorative surface; for example panel paintings, wooden polychrome sculpture, carved and/or painted wooden details in a building or on a ship.

The main objectives for the meeting 

• To present a “state of the art” for the topic
• To improve mutual knowledge and acquaintance between professionals interested in the topic of the meeting
• To provide an arena for exchange of experience and research results among professionals working with the conservation of the wooden cultural heritage, especially conservators and scientists
• To discuss techniques and materials, the criteria and methods applied for evaluating a treatment, as well as the objectives and philosophies used when deciding the aims of different treatments and how to treat an object
• To provide an occasion of discussing interdisciplinary subjects, which are very important for study and conservation of wooden cultural heritage objects (WCHOs)
• To identify the research needs

 

Participants in the meeting – the target group for the meeting

Participants in the meeting were conservators, conservation scientists, wood scientists and engineers dealing with the consolidation of wood in wooden decorated objects and other wooden objects. The meeting did bring together experienced professionals who still ask questions about the methods used and about the current philosophies when it comes to conservation of cultural heritage objects made of wood.

In total 29 participants attended the meeting, coming from 12 countries, all being COST-members.

 

The Contributions

• Keynote lectures by:

Achim Unger, University of Applied Sciences Potsdam, Germany

Jørgen Wadum, National gallery of Denmark, Denmark and

Irena Kucerova, Institute of Chemical Technology Prague, Czech Republik

• 9 orals. In addition: Achim Unger’s presentation on consolidated wood samples.
• 6 posters were presented during the Poster session.

 

Achim Unger gave a historic survey on wood consolidation treatments in Germany starting from about 1912. He discussed the composition of the consolidants used, the damages they have caused and different ways of extracting the consolidants by use of organic solvents and carbondioxide. Among his conclusions were:

• Consolidants containing mixtures of drying oils with addition of resins or resins alone causes strong damage after about 100 years.
• Leaching and extraction procedures with organic solvents or supercritical carbon dioxide can remove the aged consolidants in a limited extent only.
• New consolidants should include a potential reversibility, compatibility and re-treatability.

The problem of removing former treatments is a general problem within the field of conservation. The system showed by Unger on how to extract the consolidant is quite complex, and there is a question if an eventual paintlayer or vulnerable surface, will suffer from the “detreatment”.

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Jørgen Wadum discussed the The Panel Paintings Initiative – a multi year collaborative project initiated by the Getty Conservation Institute. The initiative is a response to the growing recognition that significant collections of paintings on wood panels may be at risk in coming decades due to the waning numbers of conservators and craftspeople with the highly specialized skills required for the conservation of these complex works of art.

The objectives of the Initiative are to:

• enhance understanding of the structural conservation of panel paintings;
• provide expertise in the structural stabilization of panel paintings to a new generation of conservators through focused residencies, workshops, and other training opportunities; and
• disseminate references and learning resources on the structural conservation of wooden panels.

 

Irena Kucerova’s lecture covered one of the main questions asked by the group attending the meeting: how to know the flow of the consolidant into the object? She discussed how to study penetration of acrylic solutions (Solakryl BMX, Veropal, Paraloid B72) into the wood.  The concentration profile of acrylates after wood impregnation was studied with Raman spectroscopy, while Neutron radiography allowed the monitoring of liquid penetration in real time. The study was done on samples of poplar and pine wood (20×20x30mm). Among other conclusions, Kucerova said that the results gained from both methods are in agreement and complement each other well, but more research is needed. An interesting aspect was that the solution used in her experiments was of a higher percentage than what would normally have been used for conservation purposes. This was a  good example on how important this cross disciplinary Cost Action is.

 

Paraloid B 72 was the most often mentioned product during the two days as a consolidant for wood, and also mentioned by Ladislav Reinprecht , Technical University Zvolen, Slovakia, who  shared with us his experience on conservation of wood with acrylics. He has among other things looked into the synthetics influence on decay processes in wood. He found that Paraloid B-72 do not increase the resistance of wood against brown-rot fungi.

When it comes to the consolidants possibility of strengthening decayed wood he concluded that Solakryl BT 55 (polybutylmethacrylate) had a slightly positive effect on the mechanical properties of biodamaged spruce wood and that it slightly increased the MOE of spruce wood intentionally damaged by the brown-rot fungus Coniophora puteana.

The conservation of two wooden sculptures (lime tree) with Solakryl BT 55 in a 22,5 % toluene solution were given as a case study. He had calculated that the theoretical solids left in the sculptures after treatment was  respectively 31.7 and 32.5%. Also in this case the percentage of the added Solakryl BT55 solution seems to be higher than usually wanted by the conservator.

To save an important surface, deteriorated wood often has to be replaced, or tunnels  and voids in the wood have to be filled. Stefan Demeter, Technical University Munich, Germany, presented the conservation and reconstruction of a Painted Wooden Tomb Chamber dating from 480 BC. This was a case were the treatment of the wooden support clearly could interfere with the paintings on the surface. The surface was treated with rabbitskin-glue as a mist, which consolidated both the paint and the wooden surface. The gaps or rather tunnels just beneath the surface of the wood caused by insects were filled with wood or putty designed for the purpose. The wooden beams are now in a museum in Munich and the fluctuating RH is not a main problem for the future conservation of the objects or the choice of treatment. Replacement of wood in various ways was also shown as a method to save the surface layer by Elżbieta Jeżewska and Krzysztof Chmielewski, from the Academy of fine Arts, Poland. Adding new wood were the old was lost was discussed as a technical as well as an ethical problem by Aleth Lorne, Private conservator, The Netherlands.

 

The change in material properties of the consolidated wood was an important issue in the discussions in the meeting. Arnold Truyen, Stichting Restauratie Atelier Limburg, The Netherlands argued that consolidation of wood is based on experience more than research based knowledge. His questions were in line with the important issues for the meeting; how do we know where the consolidants go, how do we know how deep into the structure it goes? What about possible internal tensions when a solvent is added? The drying times of solvents remain long and how do we know when the consolidation is complete? He also discussed the problems of discoloration of the wood and the “Plasticification” of the wood when consolidants like Paraloid B 72 are added.

Truyen listed some ideas and some possible research areas for consolidation of wood:

• Is it possible to develop “self healing” materials for use in wood consolidation?
• May the frass of the wood be used?
• Is it possible to use gas polymerisation; – to achieve polymerization through the introduction of individual monomers in a gaseous phase?
• Carbon-fibre (nano tubes): Can micro- or nano balloons be used?
• Can air pockets be generated in the polymer to achieve an open structure in the damaged areas without expansion pressure?

 

The importance of the surface layer as possible vapour barrier to reduce the influences of environmental climatic variations was another issue at the meeting. Ottaviano Allegretti CNR-IVALSA Italian research Council- Timber and Trees Institute, Italy, introduced an ongoing project on how the consolidation of a painted surface on wood influences the water vapour transport to and from the wood. The project aims at developing models for the prediction and understanding of the hygroscopic and deformative behavior of wooden, painted artifacts. He had looked at how various consolidants, among them: skin rabbit glue, sturgeon glue and Paraloid B72, influences the barrier effect of tempera and “oil-painted” surfaces. Allegretti concluded that the use of consolidants on the painted surface to control the permeability is not effective, and that the use of consolidants does not alter the existing equilibrium between wood and environment. Allegretti emphasizes that further research is needed.

 

Also Nanke Schellmann, Hochschule für Bildende Künste Dresden, Germany /Victoria & Albert Museum London and Imperial College, London, UK,   discussed a method for evaluating the efficiency of consolidants for decorated wooden artifacts. Her method was so far used for evaluating the treatment of the surface layer, but according to Schellmann, it also appears to be a promising mean for analyzing the changing toughness characteristics of wood consolidated with various adhesives. This is a new method and more work is needed.

The examination of the condition of the objects is often not easy as an undestroyed surface may hide defects in the structure below. Jochen Aderhold, Fraunhofer Institute for Wood Research, Germany, presented a method for non-destructive evaluation of decorated wooden artefacts with active infrared thermography.

 

The conservation of built structures was dealt with by Iben Christensen Danish Technical University, Danmark who introduced a new method on electrochemical in situ impregnation of wood with copper. The results so far imply that the method could be useful in achieving faster protection of wood already in construction.

The results of the meeting

The state of the art resulting from this meeting has some obvious limits, like the limited number of persons attending, and the limited geographical spread of the contributors. So when talking about the state of the art, it is the state of the art resulting from this meeting, not the state of the art of the topic in general.

A meeting place for professionals interested in the same topic was created during the two days. Likewise was sharing of information, of research results and other important issues made possible during the two meeting-days and for the future. This Meeting was an important arena for defining the future activities within one area of the COST-Action. A very good atmosphere, full of enthusiasm and of availability towards cooperation, emerged in this occasion, and hopefully will be maintained during future meetings and activities. The delegates expressed interest in keeping the group together and facilitate communication among the delegates.

 

New ideas came up at the meeting, but still there is a way to go before the newly introduced methods may be launched and proved useful for the consolidation, reinforcement & stabilisation of decorated wooden artefacts.

There is definitely a need for research within the field. During the meeting the following were the main questions or topics for further research that emerged:

• The idea of consolidation – what do we want? A “plastification” of the structure through added synthetics, or a support of the structure perhaps by a some added ”selfgrowing” open structure?
• The consolidant – what to use – how to apply it – how to control it
• The problem of the interface between the consolidated and non consolidated area
• The material knowledge and the skills and of the woodworker
• The need for mutual understanding and communication between conservators and scientists.

 

Day 1, Monday March 30

10:00 -11:00	Registration and coffee
11:00 -11:30	Welcome and introduction to the meeting
11:30- 12:15	Jørgen Wadum, Key note speaker Statens Museum for Kunst, Danmark The objectives of the Panel Paintings Initiative – a multi year collaborative project between the Getty Conservation Institute, the Getty Foundation, the J. Paul Getty Museum, and partners.
12:15- 13:00	Achim Unger, Key note speaker. University of Applied Sciences Potsdam, Germany Historic consolidants for wooden works of art – damage to the wood, chemical analysis and experiments for re-treatment Unger
14:30 -15:15	Irena Kučerová, Key note speaker Institute of Chemical Technology Prague , Czech Republic Studying penetration of acrylic solutions into wood with Raman spectroscopy and neutron radiography Kucerova
15:15 – 15:45	Stefan Demeter Technical University Munich, Germany Tatarlı: Study, Conservation and Reconstruction of a Painted Wooden Tomb Chamber in Phrygia (today Central Anatolia, Turkey)
15:45 -16:15	Arnold Truyen Stichting Restauratie Atelier Limburg, The Netherlands Conservation of wood – selected experiments Truyen

Day 2, Tuesday March 31

09:00 -09:10	Summing up day 1.
09:10 -09:40	Ladislav Reinprecht Technical University Zvolen, Slovakia Conservation of wood with acrylics – selected experiments Reinprecht
09:40 -10:10	Ottaviano Allegretti CNR-IVALSA Italian research Council- Timber and Trees Institute, Italy Barrier Effect to Water Vapour of Consolidant Substances on Tempera and Oil paints on Wood Specimens Allegretti
10:30 -11:00	Nanke Schellmann Hochschule für Bildende Künste Dresden , Germany (in collaboration with Victoria & Albert Museum London and Imperial College London) A new method for evaluating the efficiency of consolidants for decorated wooden artefacts
11:00-11:30	Aleth Lorne Private conservator, The Netherlands Hands on experiences on consolidation of wooden artefacts
11:30-12:30	Achim Unger Consolidation of wood – samples
14:00 -14:30	Elżbieta Jeżewska and Krzysztof Chmielewski, Academy of fine Arts, Poland Consolidation, stabilisation and reinforcement of polychromed wooden artefacts in Warsaw Academy of Fine Arts Chmielewski
14:30-15:00	Jochen Aderhold Fraunhofer Institute for Wood Research, Germany Non-destructive evaluation of decorated wooden artefacts by active infrared thermography Aderhold
15:00-15:30	Iben Christensen Danish Technical University, Danmark Electrochemical in situ impregnation of wood Christensen
Posters
	Hubert Baija: Consolidating insect damaged wood: understanding what to use. Rijksmuseum Amsterdam, The Netherlands
Drncova	Daniela Drncová: Wood consolidation: influence of liquid surface tension on its penetration into wood Institute of Chemical Technology Prague, Czech Republic
	Michal Formosa: Consolidation and reinforcement of wooden cultural heritage at Heritage Malta Heritage Malta, Malta
Kostecki	Grzegorz Kostecki: Structural consolidation and stabilisation of panel paintings Academy of Fine Arts, Krakow, Poland
	Kim Hou Petersen: Conservation of painted inventory from churches demonstrated with an example National Museum of Denmark, Denmark
	Nazeré Tojal: Conservation of a wood painted sculpture: cultural, methodological and technical issues Portugal