Optical Coherence Tomography (OCT) for the Conservation and Interpretation of Vitreous Materials in Museum Collections

Vitreous materials are glass or glass-like substance. This project is focused on the study of enamels and faience. In particular, the study of medieval Limoges enamels and ancient Egyptian faience. Areas of interest range from looking at degradation to finding out more information about the manufacturing techniques.

The PhD project studies the degradation and manufacturing techniques of vitreous objects through application of OCT combined with other analytical techniques to understand the manufacturing and deterioration processes in vitreous materials in the British Museum's collection. OCT will be the main technique employed, as well as supporting techniques such as: FTIR, XRF, SEM-EDX, Raman spectroscopy.

Specific aims of the project include:

• Analyse the degradation of vitreous objects, in particular Limoges Enamels, by combining non-invasive non-contact techniques to quantify degradation and suggest preventative measures to improve the conservation of the objects.
• Develop depth resolved material identification using OCT
• Investigate further the manufacturing techniques, specifically the glazing methods, of Egyptian Faience using OCT as well as supporting analytical techniques.

Enamelling developed and changed during the 14th, 15th and 16th centuries. During the 14th century the medieval champlevé technique was used, where channels were made in the metal layer. During the late 15th century, in Limoges, France the method for enamelling changed, this new technique meant the metal layer was treated with the enamel then painted over it. Degradation of these vitreous objects continues with conservators still trialling and testing different ways of preventative conservation.

OCT gives information about the structural composition of the enamels, giving indications on how the objects are degrading.Egyptian Faience is a non-clay ceramic material consisting of three main layers with one being a quartz core. The top layer is often a transparent glaze layer of a turquoise colour, the next layer is an interaction layer between the glaze and the quartz core and the third layer is the quartz core. There are three identified manufacturing techniques, application, cementation and efflorescence. OCT has the potential to identify or categorise the glazing method from the images.

• Margaret Read presented a poster about 3D imaging with OCT on Enamels at the biannual ICOM – CC Enamels 18 Conference held in Stuttgart, Germany.
• Margaret Read presented a poster about 3D imaging with OCT on Enamels at the Global Heritage Research Theme Showcase Event held at Nottingham Trent University on the 18th May 2018.
• A preliminary survey of a set of Limoges Enamels at the British Museum and Rangers' House (English Heritage) was conducted in May 2018 looking at the deterioration of the enamels with OCT 3D imaging complemented by XRF.

Academic Investigator: Professor Haida Liang

Co-Supervisor

• Dr Fouzia Ouali

Museum Supervisors

• Dr Capucine Korenberg
• Dr Andrew Meek and Denise Ling

PhD Student

• Margaret Read

Sponsors

• AHRC Collaborative Doctoral Award
• The British Museum

Useful Links:

• http://irep.ntu.ac.uk/id/eprint/13541/