Damage risk prediction of wall paintings with clay and earthen plaster substrates during drying

Conservation of cultural artifacts requires understanding allowable humidity fluctuations to prevent damage. Previous predictions of humidity-induced damage did not consider multilayered materials and transient moisture transfer. This study evaluated the risk of drying-induced damage to wall paintings composed of layered clay and earthen plaster. A numerical model combining poroelastic and coupled heat and moisture transfer models was developed and evaluated risks during drying under different humidity steps and rates. Results suggested that considering changing material properties would be required to predict damage risks to the originals. On the other hand, relative comparison of damage risk was effective: drying from a relative humidity of 0.7 (-) to 0.5 (-) in 6 h showed lower risk than the existing standard, indicating no damage risk. These approaches and findings support environmental control strategies for the paintings and provide knowledge for predicting damage risks of artifacts composed of multilayered materials considering transient moisture transfer.