Detection of Delaminations in Art Objects Using Air-Coupled Ultrasound°

Abstract

ABSTRACTThe possibility of using air-coupled ultrasound to find delaminations between layers in paintings was investigated. Simulations of modern paintings were constructed with hardboard as the support layer, and a layer of gesso, an animal hide glue and chalk, as the upper layer. Delaminations were introduced between the two layers. Scanning the samples using air-coupled ultrasound clearly showed these flaws. A transmitting transducer, which was 25 mm in diameter and had a focal length of 51 mm, was placed 11 mm from the back surface of the sample and an identical receiving transducer was placed 51 mm from the front surface. The transducers were operated in a tone burst mode at a center frequency of 475 kHz. Signal enhancement techniques were used to improve the contrast of the data.