Technical analysis of mid-Qing official-style Architecture polychrome paintings in Chongjing Hall of the Forbidden city

Chonghua Palace, Emperor Qianlong’s princely residence before his reign, was extensively renovated during the early Qianlong era (1736–1795). Its front hall, Chongjing Hall, retains original early-Qianlong polychrome paintings that exemplify mid-Qing decorative craftsmanship. By now, technical studies of these paintings remain limited, particularly regarding mid-Qing techniques. Therefore, this study, integrating cross-section microscopy, polarized light microscopy, fluorescent staining microscopy and SEM-EDS with archival research, conducted an in-depth analysis of the materials and execution of these paintings. Five key techniques were identified: shuase (刷色), lifen tiejin (沥粉贴金), jinzhuomo (金琢墨), hua (画), and miaonijin (描泥金). Results demonstrate the presence of complex chromatic layering and composite material systems, reflecting technological ingenuity and artistic innovation divergent from late-Qing practices. These findings provide critical technical benchmarks for mid-Qing official architectural polychromy.