Revealing the Mechanism of Ink Flaking from Surfaces of Palm Leaves (Corypha umbraculifera)

Palm leaves are the primary literary support in South and Southeast Asia before the widespread use of paper. However, palm leaf manuscripts face the threat of information loss due to the persistent issue of ink flaking during long-term preservation. Herein, we focus on studying the botanical structure, surface properties, and surface composition of palm leaves to gain an insightful understanding of the mechanism of ink flaking. According to the surface energy analysis, the surface of palm leaves is dominated by the dispersive component due to the presence of hydrophobic substances, resulting in the weak interaction between the handwriting and palm leaves. Moreover, the accumulation of silicon on palm leaves creates a “cuticle-silicon double layer”, leading to a dense structure that hinders deep ink absorption. These two main reasons are considered to cause the ink flaking easily, which is further proven by the ink flaking test with the simulated palm leaf manuscripts. To the best of our knowledge, this is the first in-depth technical study on the adhesion performance of handwriting on plant leaves. This work also provides a theoretical basis for the study of the deterioration, adhesive repair, enhancement of flexibility, handwriting reinforcement, and beyond, which contributes to the conservation of precious palm leaf manuscripts.