Tuning the surface of Korean Onggi ceramics by grinding and polishing to increase water contact angle

We demonstrate the feasibility of using polished porous Onggi ceramic tableware as food-presenting plates by modifying the water contact angle of the sintered surface. Mechanical grinding and polishing were found to increase the contact angle to values exceeding 60°. Progressive polishing with finer grit papers led, under specific conditions, to the development of a nanoscale surface layer enriched in potassium (K), aluminum (Al), and sodium (Na). During polishing, the relatively soft, low-melting glassy phase underwent plastic deformation and mixed with wear debris, locally altering its composition and forming a thin, modified post-sintering surface film. When this surface layer was removed using an ultra-fine diamond suspension, the water contact angle reverted to its original lower value. This reversible change supports the hypothesis that the enhanced concentrations of K, Al, and Na in the reconstituted surface glass phase are primarily responsible for the observed increase in hydrophobicity.