The role of coatings on the sealing of cork stoppers

Natural cork stoppers, renowned for their sealing efficacy in wine bottles, face challenges in gas-tightness due to cork surface irregularities. This study investigates the impact of lubricant coatings (silicone or paraffin emulsions), on cork stopper gas-tightness. These coatings facilitate cork conformity to glass, minimizing gaps at the interface and significantly improving sealing capacity. A small amount of lubricant leads to a two-order-of-magnitude reduction in gas flow. However, careful control of coating is crucial to ensure reliable sealing. Additionally, water absorption by cork is proposed to contribute to sealing by generating expansion forces and softening the cork, enhancing conformity to glass. This study emphasizes that natural cork stoppers should be viewed as both sealants and membranes. These findings shed light on the importance of surface treatments and water interaction in achieving reliable sealing in cork stoppers, ultimately ensuring the preservation and quality of bottled wine.