Graz researchers make Roman inscriptions readable

Researchers in Graz have developed a simple method to reveal Roman inscriptions that have become illegible, ORF reported. The team is testing the procedure on Roman stones at several locations in Styria.

Around 200 Roman stones are stored in the depot of the Universalmuseum Joanneum in Graz, but in many cases their history and significance remain unclear. Their inscriptions have become difficult to read not only because of weathering.

Some stones were later used as building materials, including as doorsteps, and were partly destroyed as a result, said Gregor Diez of the University of Graz’s Institute of Ancient Studies. Diez and a team led by Jakob Woisetschläger of Graz University of Technology, an expert in optical measurement technology, are working to make the inscriptions visible again.

The researchers use simple equipment: a commercially available ultraviolet lamp, a wildlife camera and a smartphone. Fluorescence can reveal details that are invisible to the naked eye. When an inscription is illuminated with ultraviolet light at a wavelength of 365 nanometres, traces of paint or dirt in the grooves of carved letters can become visible.

Infrared light can also reveal hidden information. The researchers use a wildlife camera for this purpose. If a stone is no more than three to four centimetres thick, an infrared through-light photograph taken from the back often provides additional clues, Diez said.

A thermal imaging camera may help when the surface has been worn down or destroyed too deeply. The researchers heated stones to 60 degrees Celsius and photographed them as they cooled. The images can reveal disturbances that sometimes allow conclusions to be drawn about letters that can no longer be read.

Roman stones are found not only in museums. Many have been built into churches and other buildings, so the research team is also working in the Hartberg area and Murau district to decipher inscriptions.