Application and Challenges of Plant Oil Detection Techniques in the Conservation of Polychrome Cultural Relics

The identification of plant oils in polychrome cultural relics is crucial for understanding historical craftsmanship and for developing appropriate conservation strategies. Historically, plant oils were used as binders, protective coatings, and plasticizers, directly influencing the stability and appearance of artifacts. Their degradation—through oxidation, hydrolysis, and environmental exposure—makes accurate detection challenging. Recent advances in spectroscopic methods (Fourier-Transform Infrared Spectroscopy, Raman), chromatographic techniques (Gas Chromatography–Mass Spectrometry, High-Performance Liquid Chromatography), and mass spectrometry imaging (Desorption Electrospray Ionization—Mass Spectrometry Imaging) enable non-invasive or minimally invasive analysis of oils, even within complex matrices. Case studies, including the Meiwu ceiling of the Palace Museum and resin–oil varnishes, illustrate how multi-method approaches improve reliability. Ongoing challenges include interference from degradation products, limited sampling due to ethical concerns, and the absence of comprehensive reference libraries. Future research should prioritize non-destructive techniques, standardized protocols, and interdisciplinary collaboration to enhance the precision and applicability of plant oil identification in cultural heritage conservation.