The Behaviour of Western Artist’s Materials in Tropical Environments
Electronic Speckle Pattern Interferometry (ESPI) and the measure of the dimensional change of Canvas Paintings
Electronic Speckle Pattern Interferometry (ESPI) has the ability to measure the deformation of materials over time. Dimensional change sensitive to one wavelength, which is not even visible under a microscope, was measured with ESPI being a non destructive optical technique incorporating simple technology. A transportable in-plane ESPI unit was built at the University of Melbourne (CCMC and the School of Physics) for use in the four institutions. An in-plane interferometer with a 633nm diode laser was used to highlight the oil paintings and then imaged with a CCD camera for computer software analysis.
The in situ ESPI measurements were taken in tropical museum environments where climatic conditions ranged from non climate controlled to intermittent or continuous use of air conditioning. In 2005 in situ analysis was undertaken and in total, twelve canvas paintings were examined. Image 11 and Image 12 shows in situ analysis in November and December 2005 at Balai Seni Lukis Negara (National Art Gallery Malaysia) in Kuala Lumpur and the Singapore Art Museum, Singapore. Results showed subtle dimensional movements of the canvas support as the relative humidity and temperature changed, as illustrated in the fringe images below.
In 2004 earlier ESPI research was undertaken by Elaine Miles, then an Honours Physics student, titled Investigation of strain in artists’ canvases due to varying humidity conditions using Electron Speckle Pattern Interferometry (ESPI) (a copy of her report can be obtained on request). Elaine is now continuing PhD studies in the Non destructive Imaging Techniques for the Investigation of Subsurface Structure in Artwork in the School of Physics with the support of CCMC. Elaine is continuing some of the earlier ESPI work including phase shifting to quantitatively determine the degree and direction of dimensional change.
Fringe images due to changes in relative humidity and temperature taken at Singapore Art Museum, National Heritage Board
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