You have seen what happens to a balloon when it is left overnight – it slowly deflates because the air inside slowly escapes. Although there are no holes or defects, and the balloon is tightly sealed, the air gradually passes through (permeates) its walls. A similar effect occurs with liquids – they slowly permeate the materials which gloves are made of. This can occur slowly or rapidly, but it will happen. When selecting a glove you must consult the manufacturer’s recommendations and refer to the “breakthrough time” (how long it takes a chemical to pass through a material) and the permeation rate (how quickly it passes through).