High-resolution tomographic analysis of microstructure and porosity in mock-ups of ancient-inspired mosaics

Abstract

This research investigates the use of Synchrotron X-ray Computed Tomography (SXCT) to study Roman mosaic mock-ups, focusing on the three-dimensional distribution of material density, cracks, and stress-strain interactions across layers. Three samples were analysed: one of stone tesserae and two of glass tesserae. High-resolution SXCT scans, using polychromatic radiation at X-ray energies above 70 keV, enabled non-invasive, microscale examination of cracks and assessment of how composition influences crack development at interfaces. Digital reconstruction and phase contrast analysis distinguished cracks from pores, revealing microstructural features and enabling quantification of pore volumes and porosity variations within strata. The results showed that stone tesserae induced more extensive cracking in the Supra Nucleus stratum than glass tesserae. These findings enhance understanding of internal microstructure and stress behaviour in mosaics, providing a basis for developing appropriate conservation strategies. Quantifying fracture dimensions enables conservators to determine the optimal viscosity and formulation of consolidants for effective penetration and stabilization, while insights on compaction and tesserae surface quality inform the design of re-adhesion and cleaning protocols that enhance cohesion and minimize future detachment. Together, these results show how microscale analysis can guide material selection and treatment strategies, ultimately supporting more durable repairs and the long-term preservation of mosaics.