Around 200 Roman stones are stored in the depot of the Universalmuseum Joanneum in Graz, the personal histories of which in many cases remain a mystery. This is because their inscriptions have become illegible – and not just due to weathering. “Some of them were used as building materials in later periods – for example, fitted as door thresholds – and were partially destroyed as a result,” says Gregor Diez, a postdoctoral researcher at the Department of Classics at the University of Graz. The researcher and the team led by project partner Jakob Woisetschläger from Graz University of Technology, an expert in optical measurement technology, are now working to shed light on the matter. And they’re doing so with simple tools: a UV lamp from a DIY store, a wildlife camera and a smartphone to take photos.
“When the inscription is illuminated with UV light at a wavelength of 365 nanometres, previously invisible details become apparent. These may include, amongst other things, traces of paint or dirt in the recesses of the chiselled letters,” explains Diez. Infrared light also reveals what lies hidden. To this end, the scientists use a wildlife camera. “If the stone is no thicker than three to four centimetres, an infrared backlit photograph – that is, an image taken from behind – often provides further insightful information,” says the researcher.
Many inscriptions can be reconstructed in this way. If the surface has been worn away too deeply or is destroyed, a thermal imaging camera may still be of help in some circumstances: “We have heated stones to 60 degrees Celsius. Images taken as they cool reveal irregularities that sometimes allow us to draw conclusions about letters that are no longer legible,” explains Diez.
Roman stones are not only found in museums today. Many have been built into the walls of churches, and sometimes other buildings. That is why the team is also out and about in the Hartberg area and the Murau district, deciphering inscriptions on site.
The project, led by Gregor Diez, was funded by the Province of Styria as part of the UFO – Unconventional Research programme. To ensure that other historians can make the best possible use of this cost-effective method for restoring the legibility of ancient inscriptions, the researchers have compiled a detailed guide. The scientific publication on this topic has just been released.
Publication
„Through a Laser Beam Darkly – Attempting a Reassessment Using Optical Diagnostics in Epigraphy”
Gregor Diez, Matthias Diez, Jakob Woisetschläger
Heritage Science 2026, https://doi.org/10.1038/s40494-026-02828-6
If you are fascinated by the society and culture of people in antiquity, you can study Ancient History and Classical Antiquities at the University of Graz.
