Optical Diagnostics in Epigraphy

This work is the result of a collaboration between the University of Graz, Department of Classics, Section of Ancient History and Epigraphy, and the Graz University of Technology, Institute of Experimental Physics and the Institute of Thermal Turbomachinery and Machine Dynamics, Working Group Metrology in Turbomachinery - Laser Optical Metrology.

ABSTRACT: In 1990, the late ancient historian Mortimer Chambers presented a work in which a weathered inscription was made visible by a laser beam shining through a 19 cm thick marble slab from behind. Criticism was not long in coming and read: “Through a laser beam darkly”. But was the criticism justified? This work attempts to answer the question of whether and how it was possible thirty years ago to make the invisible visible using a laser beam, but now with the help of various methods of highly developed modern measurement technology, with a special focus on methods that can also be used in field research. For this purpose, a marble stone with an epitaph from the 4th century A.D. was examined under laboratory conditions. This research led to the conclusion that in 1990 it was possible to make a weathered inscription visible by shining a laser beam through a block of marble, and that it is probably color pigments deep within the object that are seen as shadows when the marble is backlit by a laser beam.