Quantitative evaluations by infrared thermography in optically semi-transparent paper-based artefacts.

• Numerical model for solution of heat diffusion equation. • Thermographic investigation in optically semi-transparent materials. • Non-destructive detection of graphic features buried in cultural heritage artefacts. • Selective configurations for optical and thermal properties investigation in paper. In this paper, infrared thermography is applied to the quantitative characterization of optically semi-transparent media by using a newly introduced mathematical model. The method is specifically aimed to the detection and evaluations in graphic features buried beneath the surface of some particular kind of cultural heritage artefacts, such as books and documents. A numerical approach based on the finite element method, is proposed for solving the model equations. The computed thermographic signal depends on different inspected material physical properties, which have been selectively evaluated by comparing the theoretical results with the experimental ones in specifically designed test samples. Thereafter, the model is applied to the analysis of the results obtained in the case of graphic elements buried within samples constituted by the same previously characterized materials. [ABSTRACT FROM AUTHOR]