Proceedings e report - Firenze University Press

EFFECT OF THERMAL TREATMENT ON STRUCTURAL DEFECTS
OF MODEL PANEL PAINTINGS
Anna Moutsatsou 1 *, Eleni Kouloumpi 1 , Agni-Vasileia Terlixi 1 , Marc Georges 2 , Cédric Thizy 2 ,
Vici Tornari 3 , Michail Doulgeridis 1
1 National Gallery – Alexandros Soutzos Museum, Athens (NG), Greece
2 Centre Spatial de Liège (CSL), Université de Liège, Belgium
3 Inst. of Electronic Structure and Laser (IESL), Foundation of Research and Technology, Heraklion, Greece
Abstract
The European research project “MultiEncode” (Multifunctional Encoding System for the Assessment of
Movable Cultural Heritage) involves the use of holography for the “encoding” of structural defects of a painting
and consequently the development of a tool to confirm the originality and to diagnose the state of preservation of
the object, before and after exhibition or loan. The National Gallery’s participation includes the construction of
model panel paintings, which were holographically examined before and after thermal treatment. This paper
describes the thermal program followed and some preliminary results of the samples examination by means of
Dynamic Holographic Interferometry (DyHI).
1. Introduction
The MultiEncode European research project aims to use the advantages of holographic technology in
order to develop an innovative Impact Assessment Procedure. The proposed methodology relies on the
idea of holographic “encoding” of structural defects of an artwork that will be transported or loaned.
The selected defects are considered to form the “signature” of the object. The same defects are to be
detected again after the return of the artwork to the museum. By this way, it is possible to confirm the
originality and to diagnose the state of preservation of the object [1].
National Gallery’s participation in the project as an end-user comprises the definition of “signature
defects” of panel paintings, the construction of artificial samples that imitate original panel paintings
and the evaluation of the holographic experimental results [2]. For the construction of the model panel
paintings, an integral protocol has been developed. The protocol comprised the design, construction
and documentation of the samples, as well as the thermal treatment before and after conservation
interventions.
2. Materials and methods
A series of artificial samples was prepared, taking into consideration the typical structure of a panel
painting (for example, a post-Byzantine icon), the factors of deterioration and the type of defects that
usually occur (see Fig. 1). The main target was the simulation of all possible structures of a panel
painting (use of textile, nails, etc.), and the reproduction of all the types of defects, such as knots,
cracked wood, loss of ground and paint layers, etc. The samples were divided into 6 groups; each
group contained 3 identical samples. Thus each of the three technical partners (Centre Spatial de Liège -
CSL, Institute of Electronic Structure and Laser, FORTH Crete - IESL and Institut fuer Technishe Optik,
Stuttgart – ITO) acquired all six types of samples. Pine wood was selected, according to traditional
handbooks that suggest softwoods as substrates for byzantine and post-byzantine icons. At the
beginning, the samples were sent to the three technical partners for holographic examination and then
they were sent back to the National Gallery for thermal treatment.
Referring to thermal treatment, it has to be noticed that the present experimental procedure aimed to
provoke defects to the wooden substrates, in order to evaluate a novel structural diagnostic
methodology, without taking into account the alterations of the painted surface. For this, extended
literature research has been performed. Most of the international standards (ISO, ASTM, etc.)
referring to artificial ageing of wood, aim to test products that prevent wood degradation. Furthermore,
* E-mail: annamoutsatsou@nationalgallery.gr
Joseph Gril (edited by), Wood Science for Conservation of Cultural Heritage –Braga 2008: Proceedings of the International
Conference held by COST Action IE0601 (Braga - Portugal, 5-7 November 2008, ISBN 978-88-6453-157-1 (print)
ISBN 978-88-6453-165-6 (online) © 2010 Firenze University Press