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History of materials: a new tool for conservation of glass and ceramics

Carla Machado, Fernanda Carvalho, Marta Pessoa e Costa et Sara Martins

Résumés

Le poster met en évidence des études en cours sur les matériaux utilisés en conservation du verre et de la céramique. Dans le domaine du verre, ils sont relatifs aux matériaux de la peinture utilisés dans le vitrail, principalement liés à la production et à la compatibilité des couches de peinture dans le domaine de la grisaille et aux matériaux de nettoyage appliqués sur des croûtes de corrosion formée sur des émaux bleus. Dans le domaine de la céramique, les matériaux de conservation utilisés dans plusieurs musées portugais dans le domaine de la restauration de céramiques archéologiques ont été étudiés.

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Texte intégral

Introduction

1In the conservation and restoration of historical objects, it is crucial to have a deep knowledge of the materials and techniques used in their production and in the conservation treatments over time, in order to understand the chemical and physical properties as well as the ageing behavior of the applied materials. Therefore, the Laboratory of Glass and Ceramics from the Department of Conservation and Restoration – FCT NOVA has several ongoing studies related to these issues.

Reasearch

2In the Glass field,the study reports the conservation issues concerning painting materials used in stained-glass windows and their relation with the raw materials, the glass composition and the surrounding environment. These studies will lead us to a better understanding of the ageing and degradation mechanisms of glass and the best conservation methods.

3Technical Art History, based on old recipes found in treatises, is a valuable tool to apply to the study of the productions techniques used in the making of glass paints. In Eraclius treatise “De Coloribus et artibus Romanorum” dated from the 10th century and translated by Mrs. Mary P. Merrifield in 1848, for example, we may read:

4XLIX. [272] How to paint upon glass. I must tell you to paint upon glass. Take a grossinum of sapphire, and the scales which are beaten of red – hot iron upon the blacksmith’s anvil; and you must put one-third part of this with the grossinum, and mix it with lead glass, that is, Jewish glass, and grind it well on an iron slab and so you will be able to paint.

5Some of these old recipes, referred above, are being applied on colorless glass reproduced in VICARTE, based on 14th, 16th and 19th century glass compositions from stained-glass panels of the collection of King Ferdinand II (ill.1). The objective is to study the compatibility of the glass substrate with grisaille paint layers, using thermal analyses, such as dilatometry and differential scanning calorimetry (DSC), in order to understand the thermal properties of these two materials.

Fig.1: Historical stained glass windows

Fig.1: Historical stained glass windows

Agnes von Wittelsbach, PNP 2784

Credits: Parques de Sintra – Monte da Lua © copyright

6Stained glass panels from Palácio Nacional da Ajuda dating from the 19th century are being analyzed in order to understand the degradation of the cobalt blue enamel, with the formation of gypsum (CaSO4.2H2O) crusts, both in the surface and at the glass/enamel interface. This is a com only recurring degradation problem. Therefore new cleaning materials such as ionic liquids are being studied to restore the transparency of the stained glass/enamel.

7In the Ceramics field,a study of the materials used in the conservation of archaeological ceramics is in progress. The aim of this investigation is to make a survey, characterization and evaluation of adhesives and filling materials used in Portuguese museums, from the 1970s up to the present. Four institutions were chosen and all the treatment records have been surveyed in order to establish a chronology of the materials and techniques applied over time.

8The adhesives used in those institutions in the course of the last 45 years can be grouped into two main types – acrylics and epoxy, although other types of adhesives were found in a few objects.

9The types of filling materials did not change much over this period and consist predominantly of polyester resins, calcium sulphate and modelling putties. The polyester resins were used pure or mixed with inorganic fillers or modelling putties. In some cases, these mixtures were used just in the making of an internal structure which was then covered with a finishing layer of a modelling putty. The calcium sulphate mostly used was dental plaster. Different brands of dental plasters were analyzed by FTIR-ATR and the results did not show significant differences in the spectra. The modelling putties are generally referenced in the treatment reports without brand specification. However FTIR-ATR spectra showed that the different brands of analyzed putties have completely distinct compositions, which may be calcium carbonate or complex mixtures of calcium sulphate and silica as fillers, and a binder, for example (Fig..2).

Fig. 2 Reconstruction of a pot

Fig. 2 Reconstruction of a pot

Reconstruction made with polyester resin and modelling putty on top.

Credits: Fernanda Carvalho

10The evaluation of the current condition of these materials, by visual examination under natural and UV light, showed significant differences of colour and physical properties of the epoxy, contact adhesives and cellulose nitrate adhesives. Data deriving from this study will be assembled in a database and made available to the conservation community.

Conclusions

11It is intended that the information resulting from these studies will act as a useful aid to the understanding of the relation between production techniques and damage, and the choice of materials, and will contribute to the study of the history of restoration techniques.

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Document annexe

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Table des illustrations

Titre Fig.1: Historical stained glass windows
Légende Agnes von Wittelsbach, PNP 2784
Crédits Credits: Parques de Sintra – Monte da Lua © copyright
URL http://ceroart.revues.org/docannexe/image/5099/img-1.jpg
Fichier image/jpeg, 136k
Titre Fig. 2 Reconstruction of a pot
Légende Reconstruction made with polyester resin and modelling putty on top.
Crédits Credits: Fernanda Carvalho
URL http://ceroart.revues.org/docannexe/image/5099/img-2.jpg
Fichier image/jpeg, 40k
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Référence électronique

Carla Machado, Fernanda Carvalho, Marta Pessoa e Costa et Sara Martins, « History of materials: a new tool for conservation of glass and ceramics », CeROArt [En ligne], HS | 2017, mis en ligne le 31 mai 2017, consulté le 22 septembre 2017. URL : http://ceroart.revues.org/5099

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Auteurs

Carla Machado

Fernanda Carvalho

Marta Pessoa e Costa

Sara Martins

Department of Conservation and Restoration, Faculty of Science and Technology, Universidade NOVA de Lisboa, Portugal; Research UnitVICARTE – Glass and Ceramics for the Arts, Faculty of Science and Technology, Universidade NOVA de Lisboa, Portugal; LAQV-REQUIMTE, Faculty of Science and Technology, Universidade NOVA de Lisboa, Portugal. Study supervised by Andreia Machado, Andreia Ruivo, Augusta Lima,Joana Lia Ferreira, Márcia Vilarigues.

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Droits d’auteur

Licence Creative Commons
CeROArt – Conservation, exposition, restauration d'objets d'arts est mis à disposition selon les termes de la licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International.

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