Physics for Cultural Heritage

Multispectral imaging captures data across visible, infrared (reflectography), and UV fluorescence using CCD detectors, revealing underdrawings, pigments, and restoration layers. 

Visible imaging uses high spatial resolution cameras with professional broadband light sources to capture detailed surface textures and color distributions in cultural heritage artifacts. Macrophotography offers high-magnification imaging (1:1 ratios or greater) via specialized lenses and high-resolution CCD sensors, revealing fine details, brushstrokes, and surface defects invisible to the naked eye. Raking light applies low-angle illumination from professional sources to highlight surface topography, including raised paint, canvas texture, retouches, craquelure and panel deformations. Transillumination transmits light through thin supports like canvas or paper to reveal underlying repairs, variations in paint thickness, and hidden damage.

 Infrared reflectography (IRR) employs CCD sensors sensitive up to 1.1-1.3 μm, paired with optimized incandescent lamps emitting near-infrared radiation (roughly 760 nm to 2000 nm), to capture IR images that visualize preparatory underdrawings beneath paint layers in paintings and manuscripts. This non-destructive optical technique takes advantage of the partial transparency of many pigments and binders to near-IR light, allowing the radiation to penetrate the pictorial layer, reflect off the preparatory ground, and reveal hidden features like initial sketches, pentimenti (artist changes), signatures, dates, and underpaintings that are opaque in visible light. Its simplicity—requiring only standard or slightly modified cameras and common lighting—makes it highly practical for in-situ use, cost-effective and valuable for authentication, technique analysis, and restoration planning without risking damage to artifacts.

UV fluorescence imaging uses professional Wood lamps or UV flash systems paired with high-resolution CCD cameras to capture RGB images highlighting different pigments, varnishes, and retouches via characteristic colors (e.g., bright yellow for oils, salmon for zinc white, dark for modern retouches). This non-destructive method reveals varnish layers, differentiates binders/pigments (e.g., intense yellow for natural resins, weak for synthetics), and detects repairs darker due to less aging fluorescence, aiding restoration and authentication simply with portable, low-cost equipment.