Crimping
Pressing hair between ridged hot plates to make tight, even zigzag waves.
Also: crimped hair
Crimping makes small, sharp zigzag waves by clamping the hair between ridged heated plates, rather like corrugated card. It gives a lot of volume and a textured look and was a defining style of the 1980s, worn by pop and new wave performers. It came back in the 1990s rave scene and in the 2010s. A softer crimp can be made without heat by braiding damp hair in small plaits and letting it dry.