Download: 2004-03
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Hallmarks on silver objects can reveal much about the history of the piece. the name of the silversmith, the date of manufacture, the quality of the metal alloy, as well as other information can be determined form the study of the hallmarks. Because silver requires polishing to maintain its lustrous metallic surface, hallmarks tend to be polished away over time resulting in the loss of important historical information. Utilizing Scanning Acoustic Microscopy can recover and image of these vanished or illegible marks. Several imaging modes are presented: time resolved surface wave imaging of the near surface deformation in the silver, direct reflection images of the surface relief, and direct reflection from the silver back surface through the remnant deformed silver. The contrast in these images is caused by variations in the ultrasonic velocities in the silver, density changes, and acoustic attenuation due to the deformed silver microstructure. This technique is non-destructive, non-contact, and does not require a sample to be taken from the object.