Revealing hidden flaws: infrared thermography for detecting delamination in Chinese cloisonné enamels

The enameling process involves layering glass onto a metal substrate, often resulting in interface disconnections due to mismatched thermal expansion coefficients. This study presents the first application of pulsed infrared thermography (PT) to investigate the interface conditions between the bronze base and enamel paste layers in Chinese cloisonné enamels. A novel thermal quadrupole-based method simulates layered structures and uses thermal resistance to detect adhesion deficiencies. An automatic approach is developed to evaluate the adhesion condition of cloisonné enamels, focusing on identifying and locating characteristic peaks in the thermographic signals. Two cloisonné enamels—one from the mid-20th century and the other from the 15th century—are examined. Techniques such as thermographic signal reconstruction (TSR), pulsed phase thermography (PPT), and principal component thermography (PCT) are employed to enhance defect visualization. Abnormal areas are subsequently analyzed for interlayer thermal resistance. The proposed automated assessment method proves highly effective and efficient in evaluating thermal contacts, offering a valuable tool for preserving and studying cloisonné artifacts.