A spectral imaging methodology for determining on-line the optimum cleaning level of stonework

This study aims to introduce a new spectral imaging methodology that can be used to monitor on-line, non-destructively and in situ the cleaning level of pollution encrustation on stonework. The suggested technique is based on the optical properties of monochromatic light penetration in matter. The calculated differences of images, obtained at two different spectral bands, could reliably map the depth of cleaning. This novel approach was tested in the laboratory during laser cleaning trials on polluted stonework enabling high accuracy measurements (such as the detection of thin crust layers remaining on the under-cleaned marble surfaces). However, it may also apply for the monitoring of any other cleaning technique (micro air-abrasive, etc). A detailed presentation of the results will be demonstrated while the potential of its wide application on everyday conservation practice on stonework will be discussed.