Ancient Chinese murals are precious cultural heritage and vulnerable to structural defects like cracking and delamination, which severely impact their preservation. To address early damage detection and deepen mechanistic insights, this study applies fluorescence stress-sensing technology using mechanochromic 1,1,2,2-tetrakis(4-nitrophenyl)ethene (TPE-4N) coatings on laboratory mock-ups. Under UV light, microcracks (tens of microns) were visualized, quantified, and monitored via photographic analysis. Environmental aging tests revealed distinct defect patterns including failure within pigment layer (cracking) and interlayer debonding (cleavage, cupping, and lifting) with crack propagation rates quantitatively analyzed. Elevated adhesive concentrations and humidity variations exacerbated defects and influenced pigment layer failure modes due to the combined effects of pigment layer strength, interlayer bonding, and stress. Furthermore, crack-propagation dynamics in most samples exhibited three characteristic phases: induction, stable development, and saturation, underscoring the necessity for fatigue monitoring in cultural relic conservation to prevent sudden failure.

Dew is a common but important phenomenon. Though water is previously considered to be a threat to earthen heritage sites, artificial dew is showing potential in relic preservation. A model of dew prediction on earthen sites will be essential for developing preventive protection methods, but studies of dew formation processes on relics are limited. In this study, a two parameter model is proposed. It makes approximations according to the features of earthen heritage sites, assuming that a thin and steady air layer exists close to the air–solid interface. This semi-theoretical model was based on calculations of the mass transfer process in the air layer, and was validated by simulations of laboratory experiments (R > 0.9) as well as field experiments. Additionally, a numerical simulation, performed by the commercial software COMSOL, confirmed that the difference between fitting parameter δ and the thickness of assumed mass transfer field was not significant. This model will be helpful in developing automatic environmental control systems for stabilizing water and soluble salts, thus enhancing preventive protection of earthen heritage sites.

This paper presents scientific analyses of the wall paintings in Wudang Lamasery, which is located in the Baotou area of Inner Mongolia, China. Raman spectroscopy was used to analyze the pigments of the mural of the Lam rim Hall. The results show that vermilion, red lead, chrome yellow, emerald green and synthetic ultramarine were used. The existence of synthetic pigments provides a clue for the date the mural was painted.