An elastomeric surface has been oxidized to give it a glassy skin. When exposed to solvent vapor, the elastomer swells but is restricted by this stiff skin, causing the surface to wrinkle into interesting patterns. Here, we see the wrinkling spread across the surface by a propagating front. As the sample continues to absorb vapor, the straight buckles begin to morph into a zigzag or "herringbone" pattern, and defects in the pattern begin to appear. |