What is osmotic blistering?

Osmotic blistering occurs when moisture penetrates a coating, leading to the formation of blisters. This process involves subcoating water diffusion through a film, which creates internal pressure as it reacts with contaminants or dissolution products in the substrate. The resulting osmotic pressure can force the coating away from the surface, leading to visible blisters.

Understanding this phenomenon is crucial for paint inspectors, as it highlights the importance of properly preparing surfaces and ensuring that coatings are applied in conditions that minimize moisture exposure. It also emphasizes the role of barriers and sealants in protecting substrates from moisture, which can ultimately prolong the life of the applied coatings and maintain the integrity of the structures they are designed to protect.