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Abstract
This paper presents and compares two conservation-restoration methods of wooden supports deteriorated by old-house borer (Hylotrupes Bajulus) biological attack. Research of paint layer surfaces has shown that supports are irreversibly changed by the addition of new materials of the same or a different nature than the original, or by the transfer of the paint layer to a different support. This type of operations leaves specific traces transforming the original by altering it permanently. For this reason a different approach to the problematic of support decay due to biological attack was sought, by avoiding to complete unnecessarily the wood support where the paint layer is sufficiently supported by the substrate. The proposed method is based on the mechanical reinforcement of the broken resistance structures with balsa wood, according to a pre-determined order of priorities.
The mindset formed from conservation practice is that the missing timber due to biological attack should be completed with a quantity of material equal in volume, be it wax, glue, Paraloid, synthetic materials or plaster, etc. These materials are selected because once introduced into the wood support they pass from liquid to solid state. We believe that introducing into the support materials, such as consolidants that become irreversible in time, exceeds the competence of the conservator-restorer, whose duty is to prolong the lifespan of the work of art in its original state, without changing it. Supports are changed by the addition of new materials of the same or a different nature than the original, or by the transfer of the paint layer to a different support. This type of operations leaves specific traces transforming the original by altering it irreversibly.
For that reason a different approach to the problematic of support decay due to biological attack was sought. A careful analysis of the work of art before the conservation treatment has shown that: 1) Biological attack breaks the structural resistance of the wood and thereby endangers the existence of the work of art as a whole. 2) After a massive biological attack the weight of the wood required to support the paint layer decreases. Weight measurements have shown that the wooden panel is normally oversized for the paint layer it supports. Hence, we sought to respond these issues that occur before the conservation treatment, as follows: 1) In response to the first problem, we tried to connect the broken resistance structures mechanically with balsa wood, according to a pre-determined order of priorities (depending on factors such as the mounting system, the presentation of the work within the iconostasis ensemble, the compression / traction forces that take place during the completion with new wood, etc.).
2) In response to the second problem, we avoided to unnecessarily complete the wood support where the weight of the paint layer was sufficiently supported by the substrate.
From left to right:
Figure 1-3. Extreme degradation of the support due to biological attack. The support hastransformed into a “box” with very thin walls filled with a mass of sawdust. Figure 4. Aspect of an icon before conservation. Figure 5. Detail of support damaged by biological attack.
Our team was involved in the conservation of two iconostases that presented these specific problems: the Church of Humor Monastery and the Arbore Church.
The two iconostases showed similar conservation problems: both present the same forms of degradation due to widespread biological attack, which caused major degradation of the colour layer.
These forms of degradation were identified as being produced by the old-house borer (Hylotrupes bajulus) that has 3mm as a larva and reaches 10-20mm when mature. It is black or brown, elongated by decorated sheaths and has a life cycle of 3 to 10 years. The galleries it creates are branched and disposed in levels.
A) At the Church of Humor Monastery, the most severe forms of degradation were present in the centre of the iconostasis at the Apostles register level. The support structure of the iconostasis was weakened at the level of the right column and in all the inferior area, destabilizing the connection between the components. The register of Apostles from the central area - Deesis scene – presented extreme degradation due to biological attack: the inside of the support was practically turned into fine powder and the support behind the paint layer was transformed into a “closed box” with very thin walls that held inside a mass of sawdust with flour consistency. The support of the icons consisted of a thin layer behind which the wood was converted into powder. Moreover, if turned upside down, the content of sawdust would move to the other side, as in an hourglass. The entire ensemble was in danger of implosion, collapsing inwards. The reverse is painted in a decorative manner and shows traces of rough trimming, element that provides historical research data. Thus, the iconostasis requires a complete conservation-restoration intervention on both sides. B) At Arbore, the iconostasis presented most of the same problems. Moreover, 80% of the thin frame of the back of the iconostasis that sustained the ensemble was affected by biological attack. The only element that was still resistant was the beam that connected the north and south walls, which remained the pillar of strength to enhance the resistance of the whole iconostasis structure. The support of the iconostasis from Arbore was built in situ on five registers attached and connected between them through mechanical “plug” type connectors, then it was plastered and completed by the application of metal leaf and paint layer. Thus, an eventual detachment of the elements from the iconostasis was impossible without jeopardizing the original. Therefore, the back and the resistance frame of the iconostasis were restored in situ. In this paper, we wish to draw attention to our approach to the conservation methodology and treatment. Our treatment proposal starts from the premise that wood structures contain a percentage of moisture and thus, the introduction of consolidants (wax, colophony, varnish of any kind, or any other injectable consolidating material) will reinforce the structure only apparently and will cause irreversible degradation to the wood structure by filling the wood fibre. With time, these filled structures are left without the ability to produce a regular exchange with the relative humidity of the microclimate and turn into dust, losing their ability to contribute to the resistance of the wood support. Therefore, the conservation of wood structures decayed by biological attack requires a pragmatic approach based on a technical thinking, with attention to the details of the wood structural resistance. The intervention is necessary and appropriate only in those cases when the structural support resistance is compromised inducing degradation of the paint layer. Even in this case, the intervention must be limited solely to the consolidation of those structures that are necessary to the resistance of the ensemble. In case the resistance of the structures is not affected we can say that once stopped, the biological attack removes a part of material that is of no use as long as the scope of the support is to sustain the colour layer; the support is often oversized when compared to the paint layer. Therefore, it is very important to know the actual weight of the layer of paint (together with the ground) to be supported by the wood structure. After determining the weight of the paint layer at the two monuments we found that at Humor it has 31.4 kg ± 3% for 35 square meters, and at Arbore cca. 54.8 kg ± 3% for 54 square meters. However, the support and the resistance structure that are sustaining the above values are in fact capable of handling cca. 443 kg in the first case and cca. 657 kg in the second. The fact that the structure was built on a fixed scaffold with the extremities fasten into the north and south walls increases its ability to support more weight, which can become 1000 times bigger than that necessary to support the colour layer. The two types of forces that are generated - compression (from the layer of paint) and bending (at the back of the iconostasis) - can be obtained by the following mathematical formula to calculate the bending strength:
Where: - P is the force that breaks the sample (expressed in newtons, N); - l is the distance between the resting points of the sample (expressed in meters, m); - b is the base of the sample’s cross-section (expressed in meters, m); - h is the height of the sample’s cross-section (expressed in meters, m). Of course, this formula is not really needed to calculate the strength of a structure to see whether it can support or not the colour layer! This exercise only helps us understand that in general the wooden support behind the paint layer is oversized and when biological attack occurs, we can consider that it diminishes a useless ballast. Our approach angle should be that of understanding the relation between the overall and its components and that the conservation of timber that suffered a widespread biological attack is a matter of reinforcing the structural resistance and not a matter of filling, of replacing old timber with new one or of consolidation with natural or synthetic products. The problem of timber consolidation by injection is old and was already mentioned in the 18th century by Dionysius of Fourna in “The Painter's Manual”, in the section that speaks about "How to repair an old and decayed icon": "When you want to repair an old and decayed icon, do this: if the back of it is rotted and worm-eaten, first clean off the rotten parts thoroughly and shake off the dust. Then soak it in glue so that the panel is well impregnated and put it in the sun to dry; only be careful not to let the glue go through to the other side and ruin the painting. Next take some sawdust and mix it with glue and fill the holes with it; when it is dry either give it a gesso covering or strengthen it by gluing some cloth on to the back”. Since then, it has been generally sought to replace the material of the damaged support with a new one occupying the same volume. The same is true today with the use of synthetic products injected in the work of art. To better understand the real impact of consolidation by injection with organic or synthetic products, an experiment was carried out in which the penetration depth of the consolidants was measured in ideal conditions. The aim was to see how deep the consolidants can penetrate into the sample and how many structures it can link between them. To that end, a cardboard box was constructed and filled with fine sawdust extracted from an icon. For the first test, an aqueous solution of skin glue at 6% was injected and for the second, a Ketone solution of Paraloid B72 at 4%. In both cases 10 ml of consolidant were injected. The results were very clear and similar in both tests: the consolidants do not penetrate as deep as would be ideal, but when placed into the sample, they are instantly surrounded by sawdust which basically stops the further penetration of the solution inside, forming a compact bowl that does not regenerate the cohesion of the wood destroyed by biological attack. This is due to several reasons such as the different polarity of the component materials, the hydrophobic substances in the wood composition and the surface tension among other. In case such degraded support is injected at several points, we obtain a series of bowls, which unnecessarily increase the weight of the icon, without achieving the consolidation effect. Moreover, we introduce into the work of art a new material which has its specific particularities, creating tensions other than those of the icon, and that has effect on the colour layer, the ageing cracks, the fissures along the fibre, etc. It is known that all the materials introduced into the work of art produce specific types of degradations that eventually reach the surface of the paint layer, altering its integrity and particularities. This is especially true for the support, which greatly contributes to the production of ageing cracks and fissures on the surface of the paint layer. By employing these methods and knowing their effects in time, we simply change the normal lifespan of the work of art and thereby violate one of the principles of conservation, namely to preserve the character of the work of art as it has reached us. Operations such as the transfer of the paint layer on a new support with the same age and essence as the original and parquetry operations have the same shortcomings, the final result being the same, i.e., changing the specific features of the work. In what concerns the manual of Dionysius of Fourna, it responded to 18th century demands which were very different from those of today. Then, the artwork had to primarily represent and literary describe the reality, and for this it had to be as complete and linear as possible so that the message would be quickly learned. Today the conservator-restorer is asked to preserve the original as a matter of collective memory and a valuable experience, which lays on the foundation of the contemporary thinking that he /she needs and supports. Taking into consideration the above methods and knowing their results, it was decided to establish the exact issues that needed to be addressed and then choose the most appropriate conservation method. The conservation state of the icons from Humor, previously described, did not allow us to intervene on the front or the back because of the existence of a paint layer which was decided to be preserved. Also, the need to remount the icons on the iconostasis in their places, vertically and resting on their bases, forced us to intervene on the sides of the icons. Our aim was to restore the links between the healthy structures inside icons, considering that this will restore the initial mechanical strength of wood substrate, while adding an amount of new timber as low as possible.
Figures 6-10. General view and details of an icon's support. Consolidation of the resistance structures, connected mechanically with balsa wood.
Figures 11-15. General view and details of an icon's
support. Consolidation of the resistance structures, connected
mechanically with balsa wood.
The resistance structures were mainly strengthened from the basis of the icons towards the vertical axis. These structures had the most important contribution to the conservation of the icon. Afterwards the edges that had the role of closing structures between the verso and the front were mounted. The mounting of complete reinforcement structures on the sides of the icons induced new tensions that had to be counterbalanced by opposite forces. Conservation interventions were performed according to the priorities established in the beginning, which stated that the first priority should be given to the reconnection of the healthy structures between them, on the path of the forces that discharge at the basis. The second priority was the construction of the resistance support according to the mounting type of the icons on the iconostasis. If the icons would have had a different mounting system on the iconostasis, the interior structure would have been built with another configuration. The third priority was finding the correct and equilibrated rapport between the original and the newly introduced forces, with as little addition of wood as possible and the minimum contact of this material with the original. This was achieved by creating mobile connections between the new structures and half-mobile connections between these last structures, by constructing counterforce elements using materials with different flexible capabilities and by using wood of different thicknesses.
Figures 16-19. General views and details of two icons' supports. Consolidation of the resistance structures, onnected mechanically with balsa wood.
At the iconostasis from Arbore, the conservation approach took into account the specific state of degradation of the paint layer in relation to the support. Because this layer presented a good adhesion to the substructures from the immediate vicinity (about 5 mm depth) and because deeper inside the support the connections were destroyed by the biological attack, it was considered that the most appropriate approach would be to link the substructures between them, from the paint layer inwards. This was achieved by introducing a number of approx. 2400 elements made of acacia wood with thickness less than that of the flight holes, that were placed inside them to take over the bending forces of the support. In this context, measurements to determine the weight of the component layers were made, as follows: A) The paint layer weighs ~54.8 Kg. This value was obtained by measuring a sample of 8 grams and multiplying it by the total area of the iconostasis. B) The support weighs ~657 kg. This value was obtained by measuring the mass of several detachable support elements. The support is able to withstand a weight 10 times bigger, i.e., 6.570 kg. Afterwards it was proceeded with the localisation and identification of the healthy structures on the back of the icons. These were linked between them with wooden rods placed through the flight holes in anchor type connections with cross direction. After drying the new materials introduced into the work of art it was found that the support has a visibly improved resistance and the paint layer has a better adhesion to the substrate.
Figures 20-22. General view of some icons from the Apostols register after conservation treatment.
Figure 23. Final aspect of the isonostasis from the Church of Humor Monastery after conservation. 1. Consolidation by different types of injection with various consolidants, whether of animal or synthetic nature, does not solve the problems of cohesion between the layers of timber damaged by biological attack. The consolidation of the support by the injection of different solutions should only be used where tests confirm a positive result and where other methods of consolidation may not apply. 2. The transfer to a new support made of different type of wood, or to other types of support, can cause major degradation of the paint layer, causing an accelerated degradation rather than a consolidation of the support (eg., through new cracks due to the shrinkage forces of the fibre of the new wood introduced into the work). 3. The treatment of the timber that has suffered a massive biological attack should be addressed by focusing the attention to issues such as the resistance of the component structures and the tensions between them, the interpretation of the objects based on their location after the conservation treatment and the conditions of micro and macro climate in which the objects will be preserved. Resistance problems must be resolved by the use of wooden elements that balance each other in terms of stress, and which must be put into the work by “welding” points and not by applying adhesive on the entire contact surface. Elements of new wood should be used so as to follow the path of the old wood resistance structures.
About the authors
Cornelia Sãvescu and Dinu Sãvescu
Conservator-restorersContact: contact@savescu.com Cornelia Savescu is a panel paintings conservator. She has a degree in Monumental Art and Restoration (1984) from the Fine Arts Institute “Nicolae Grigorescu”. She specialized in the conservation of panel paintings (1985-1988) at the Centre of Professional Training in Culture (CPPE) of the Ministry of Culture and National Heritage. She worked as a conservator at the National Art Museum in Bucharest (1984-1987) and was a lecturer at the National Art University, Conservation-Restoration Department. Dinu Savescu has a degree in painting (1984) from the Fine Arts Institute “Nicolae Grigorescu”. He specialized in the technique of oil painting on wood and canvas (1985-1988) at the Centre of Professional Training in Culture (CPPE) of the Ministry of Culture and National Heritage. He worked as a curator / conservator at the National Art Museum in Bucharest (1984-1987). He is a member of the Romanian Fine Art Association, Painting Specialty. Cornelia and Dinu Savescu have worked for more than 20 years in the conservation of panel paintings and other wooden objects and works of art. Their experience includes complex conservation projects such as the Iconostasis of several monuments from Romania (Sf. Silvestru - Bucharest, Voronet, Moldovita, Humor, Sf Gheorghe – Iasi, Kretzulescu), conservation of furniture and frames, and restoration of icons (15-19th century) and oil paintings on canvas in private collections from Romania, Greece, Germany, Switzerland. They participated in national and international research projects and workshops, published several specialty papers and have a rich expositional activity.
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