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Highlights in Chemical Technology

Chemical technology news from across RSC Publishing.

Instant insight: Science and art in harmony

24 September 2007

Marc Aucouturier, Centre for Research and Restoration of the Museums of France, and Evelyne Darque-Ceretti, Paris School of Mines illustrate the benefit of a multidisciplinary approach to preserving our cultural heritage.

Lustred ceramic fragments

All that glitters is not gold: glazed ceramic decorated with metallic luster, a very thin layer of vitreous glaze in which are embedded copper and silver nanoparticles.

The understanding and preservation of cultural heritage has been a major challenge for all civilisations. The most modern tools of materials science are rising to the challenge. Knowing the composition and rebuilding the history of an artefact needs sophisticated laboratory instruments and a long enquiry involving intensive collaboration between materials scientists and art historians. Data on the physical constitution of an artefact, its authenticity, its history, the circumstances of its discovery, its treatment after being abandoned and/or stored, are useful not only to increase our knowledge of civilisation and art history, but also to inform conservation policy.

"The application of surface science to cultural heritage materials has undergone a dramatic development in the past few decades, thanks to the impressive improvement of analysis and investigation equipment"
The study of cultural heritage artefacts and their preservation and restoration begins with - and is often limited to - a comprehensive characterisation of their surface by non-destructive methods. The application of surface science to cultural heritage materials has undergone a dramatic development in the past few decades, thanks to the impressive improvement of analysis and investigation equipment.

One example of objects recently submitted to in depth investigation are beautiful ancient ceramics with a metallic lustre decoration. This technique was born in the 9th century in factories created by the Arabs during their conquests in Mesopotamia, Egypt and Persia. With the passing of the centuries, Arab potters spread their know-how all over the Islamic world. It reached Spain and was finally transmitted to the workshops of the Italian Renaissance at the end of the 15th century, giving rise to what is known as majolica ceramics. Lustred ceramics attracted the attention of conservators and scientists on account of the structure of the thin surface film that is responsible for their specific aspect. They exhibit an iridescent shine that sometimes imitates a gold, silver or copper deposit in specular reflection and appears from deep red to bright yellow by diffused light observation. In order to understand this very sophisticated technique and trace its propagation through the ages, a series of investigation were conducted in several materials science laboratories. They showed that the surface film is made of vitreous matter in which nanoparticles of metallic silver and/or copper are embedded. In other words, ancient Islamic potters invented nanotechnology eleven centuries before our solid state physicists.

"Ancient Islamic potters invented nanotechnology eleven centuries before our solid state physicists"
Another example of an ancient decoration technique that is still not fully understood is 'black bronze'. It is the result of intentional surface treatments by ancient craftsmen in order to change the surface aspect and colour of bronze artefacts. It was discovered on bronze artefacts from Egypt (2nd millennium BC), the Roman Empire (1st century AD), China (4th century AD) or Japan (14th century AD). It consists of a chemical treatment applied to specific copper alloys containing always gold (1 to 8 wt%) and/or silver (1 to 4 wt%) in order to give them a black or velvet colour. A comprehensive study has been conducted recently on a large body of Egyptian and Roman Empire pieces from the Louvre museum in France. Most of the black patina appears to be pure cuprite, Cu2O, containing small amounts of gold and/or silver. The natural colour of cuprite is red, and the research on the role of the precious metals on its black coloration is still under investigation.

Many other examples could be given, such as the fruitful application of Raman spectroscopy to the identification of pigments and the restoration of painted artefacts, the use of analytical spectroscopy to organise a preservation policy for the Swedish warship Vasa, the study of environmental degradation of medieval stained glass windows by secondary ion mass spectroscopy or the identification of degradation mechanisms of old paper manuscripts by spectro-photometry and atomic force microscopy.

Read the full Tutorial Review 'The surface of cultural heritage artefacts: physico-chemical investigations for their knowledge and their conservation' in issue 10 of Chemical Society Reviews.

Link to journal article

The surface of cultural heritage artefacts: physicochemical investigations for their knowledge and their conservation
Marc Aucouturier and Evelyne Darque-Ceretti, Chem. Soc. Rev., 2007, 36, 1605
DOI: 10.1039/b605304c

Related Links

Link icon Centre de Recherche et de Restauration des Musées de France
Read more about Aucouturier's research

Link icon Centre for Materials Forming, Ecole des Mines de Paris
Read more about Darque-Ceretti's research

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