|
Limoges enamels along with a lot of glass-based objects suffer from deterioration that affects the condition, structure and longevity of the pieces affected. Understanding the mechanisms and causality of this deterioration can aid in conserving and preserving the wares in an optimal manner. Limoges enamels are composed of multiple layers of glass over a metal substrate, multiple colours and levels of opacity are used with gildings and paillons to create vibrancy and decoration within the artwork. A main concern is the exposure of the glassware to moisture and pollutants that can cause crizzling, cracking and spalling of the enamel and cause detrimental and irreversible damage. Detection and analysis of the moisture content, progression of the gel layer (a compositionally modified layer formed on the surface of the glass due to the attack from moisture or pollutants), and overall subsurface condition of the enamels can help give insight into the level of deterioration. Furthermore, some enamels and certain colours show worse levels of deterioration. Is this a product of the environmental conditions of storage or the composition of the enamels? Non-invasive analytical techniques are a priority in analysis of cultural objects; therefore, multiple non-invasive techniques were employed to survey and analyse eight Limoges enamels from the sixteenth century in the British Museum collection. These techniques were 810nm Ultra-High-Resolution Optical Coherence Tomography (UHR OCT), 400-2300nm Fibre Optical Reflectance Spectroscopy (FORS), X-Ray Fluorescence (XRF), VIS/NIR (400nm-850nm) spectral imaging (PRISMS) and Shortwave Infrared (1000 – 2500nm) spectral imaging (SWIR). UHR OCT images the structure and level of deterioration throughout the enamel by showing the extent of the gel layer in the glass, as well as the structure and condition throughout the top layer. SWIR can be used to give information on the level of hydration in the glass across the entire enamel, this is mapped in 2D over the entire enamel for analysis. XRF has been used widely in glass analysis and can help identify the composition of the glass. PRISMS results give information on the spectra in the visible/NIR region complementing elemental analysis by XRF, it is useful in this investigation as a standardised way to analyse spectra and categorise the spectra and colour of an enamel. By using a combination of all of these techniques, investigations were conducted to understand if there is a link between the composition and deterioration of the selected sixteenth century Limoges enamels. Results using the OCT and SWIR analytical techniques have already shown a strong link between the level of hydration and the level of structural deterioration in these Limoges enamels, further analysis showed there was a correlation between the depth of the gel layer and the level of hydration. Furthermore, when incorporating all the techniques, initial findings have shown interesting insights into how the composition can affect the deterioration of these enamels.
|
