Speakers
Description
Soapstone (steatite) is widely documented as a quarried material; Alpine and Scandinavian contexts provide well-known examples in monuments, archaeological quarry landscapes, and utilitarian artefacts such as cookware. Its technological relevance derives from distinctive thermophysical properties, notably efficient heat transfer and rapid transient thermal response, which govern surface heat exchange. These properties affect processes of direct interest in cultural heritage, including moisture cycling and thermally induced stress fields, and may modulate near-surface microclimatic conditions in quarry environments. Quantitative characterization on real stone surfaces, in the laboratory and in situ, therefore requires non-invasive methods compatible with access constraints and heritage-preservation requirements. The workflow is applied in situ at the Caurga trench quarry (Parco del Paradiso, Chiavenna) and on oriented samples from Chiavenna Unit lithotypes, enabling direct laboratory–field comparison. Thermal diffusivity is measured within a quantitative infrared thermography framework using laser spot thermography in reflection. A portable low-power laser imposes a quasi-Gaussian circular heat input on a planar surface, and a radiometrically calibrated infrared camera with macro optics records the time-resolved two-dimensional temperature field during heating and subsequent cooling. Diffusivity is estimated by fitting the temporal evolution of spot spreading, quantified by the effective radius or spatial second moment, to analytical or numerical solutions of the two-dimensional heat equation. In-plane anisotropy is derived from directional analysis of the spot broadening, providing constraints on direction-dependent thermal transport. Repeatability and uncertainty are assessed through replicate acquisitions, radiometric calibration, and sensitivity analyses to emissivity assumptions and segmentation procedures. Moisture effects are investigated by IR thermography through the Spilling Drop Test (SDT). The thermal transient induced by a fixed-volume droplet is used to derive cooling-curve descriptors, and droplet segmentation and thresholding strategies are tested to ensure reproducibility across lithotypes and measurement conditions. SDT metrics are interpreted together with laser-based diffusivity and complementary material characterization, including X-ray diffraction, bulk density and water-accessible porosity from immersion methods, water imbibition capacity, specific heat, and ultrasonic P- and S-wave velocities with derived dynamic elastic moduli. Microclimatic implications are assessed by integrating lithotype-specific thermophysical parameters with near-surface temperature and humidity monitoring and local meteorological series. Surface energy exchange is interpreted using the Bowen ratio method. This combined approach supports site-scale characterization of soapstone thermal behavior in geoheritage and built heritage contexts.
