Artwork restoration without destruction
Stratigraphy, the study of the internal paint layers of a painting can reveal a great deal of information for the historian. Up to recently, to renovate or even study historic works of art, a micro-sample had to be taken by means of an invasive procedure for analytical spectroscopy. As many artworks are extremely valuable or very vulnerable, even sampling on a micro-scale can be very damaging. To avoid inflicting further damage to priceless pieces, the 'Development of a novel and integrated portable non destructive analysis system for the documentation of artworks' (Infrartsonic) project developed a completely non-invasive method to determine a painting's profile. Information on the local distribution of the pigments in each layer is also available using the new portable technology. Acoustic microscopy combined with diffuse reflectance spectroscopy give a complete depth profile and a map of the pigments in each layer. Using ultra high frequency ultrasound, acoustic microscopes operate non-destructively and penetrate most solid materials to make visible images of internal features, including defects such as cracks and delaminations. The spectroscopy element defines which pigments occur and in what position. For the pigment mapping element, special algorithms have been developed using the Kubelka-Munk theory. Involving reflectance of light from paint films, the resulting system can detect any under-painting or previous restoration attempts, critical information for both historians and restorers. The final product is a 3-D model displaying the paint structure in any area of interest. Three prototype devices have been developed at different Infrartsonic consortium labs. For more detail, there is a website at http://www.infrartsonic.org/Default.aspx giving full technical details of the system as well as a list of relevant articles. The technological advances of Infrartsonic, along with being non-invasive and portable, will no doubt be invaluable to the preservation of the world's irreplaceable artworks. Museums and archaeologists will be able to analyse and restore historic paintings without danger of irreversible damage.
