Sparkling wine
Sparkling wine corks are mostly built from three sections and are referred to as agglomerated corks. The mushroom shape that occurs in the transition is a result of the bottom section's being composed of two stacked discs of pristine cork cemented to the upper portion, which is a conglomerate of ground cork and glue. The bottom section is in contact with the wine. Before insertion, a sparkling wine cork is almost 50% larger than the opening of the bottle. Originally, the cork starts as a cylinder and is compressed before insertion into the bottle. Over time, their compressed shape becomes more permanent and the distinctive "mushroom" shape becomes more apparent.