Scotch tape has been a household mainstay for nearly a century, but it still holds some scientific surprises. Researchers have discovered that the screeching sound emitted when one rapidly peels Scotch tape—akin to the screech of fingernails on a chalkboard—is the result of shock waves produced by micro-cracks propagating along the tape at supersonic speeds, according to a new paper published in the journal Physical Review E.
It was a 3M engineer named Richard Drew who developed the first transparent sticky tape in 1930. The impetus came from car manufacturing, specifically two-color designs, where the adhesives used were so sticky they often removed the paint when peeled off; the paint then needed to be manually touched up. Drew found a sandpaper adhesive with just the right amount of stickiness and used it to coat a roll of cellophane tape. (Fun fact: Drew also co-invented the snail-style dispenser for the tape with his 3M colleague, John Borden.) The tape was hugely popular during the Great Depression; consumers used it to repair everyday items rather than replace them. That popularity has never waned.
Scotch tape has also generated considerable interest among physicists. Back in 1939, scientists noticed that peeling tape could produce light—specifically, a glowing line where the tape end pulls away from the roll. The phenomenon was first recorded in the 17th century and is known as triboluminescence: the generation of light when a material is crushed, ripped, rubbed, or scratched. Diamonds, for instance, sometimes glow blue or red during the cutting process, while ceramics emit yellow-orange light when being cut by abrasive water jets.
The most popular example is Wint-O-Green Life Savers: crush the candy in a dark closet and you can see the sparks produced. It’s the sugar crystals that produce the effect: the crushing action rips electrons from the molecules, which leap across the gap to the more positively charged side. The jumping electrons collide with nitrogen atoms in the air, which briefly absorb the energy and then emit UV light. The effect is made visible by the wintergreen oil used for flavoring, i.e., fluorescent methyl salicylate, which absorbs UV light and converts it into blue light.
In 1953, Russian scientists peeling Scotch tape in a vacuum reported detecting electrons with sufficient energy to emit X-rays. Other scientists were skeptical, but this phenomenon was finally confirmed in 2008, when UCLA physicists produced X-rays while unwinding a roll of Scotch tape in a vacuum chamber. The goal was to harness triboluminescence for X-ray imaging, and the team produced a low-quality X-ray image of a lab member’s finger (see image below). Fortunately, this only works in a perfect vacuum, so everyday Scotch tape users are safe.
A shock to the system
Peeling Scotch tape produces sound as well as light, typically attributed to the slip-stick mechanism at play during the peeling process. In 2010, co-author Sigurdur Thoroddsen of King Abdullah University in Saudi Arabia and colleagues used ultra-fast imaging to identify a crucial micro-fracture phenomenon of the slip mechanism: a sequence of transverse cracks that travel across the width of the adhesive at supersonic speeds. A follow-up 2024 study found a direct correspondence between the screeching sound and those transverse cracks, but did not identify a mechanism.
That is the purpose of this latest study. Thoroddsen et al. wondered whether the sound was directly generated by a crack’s rapidly moving tip, which would also produce the distinctive discrete sound wave pulses associated with peeling Scotch tape. The authors experimentally tested their hypothesis by conducting simultaneous high-speed imaging of the propagating fractures and the sound waves traveling in the air. They manually unpeeled Scotch tape using a metal rod, capturing the cracks with two video cameras and the sound with two microphones synchronized to the video camera, the better to pinpoint the origin of the pressure pulses.
Their results showed that the screeching arises from a train of weak shocks that culminate when the transverse cracks reach the edge of the tape. The supersonic speed at which they travel, relative to the surrounding air, is crucial to the generation of those shockwaves. “A partial vacuum is produced between the tape and the solid when the crack opens,” the authors explained. “The crack moves too fast for this void to be filled immediately, even though air is sucked in from the direction perpendicular to the crack. The void therefore moves with the crack until it reaches the end of the tape and collapses into the stationary air outside.” Each time a fracture tip reaches the edge of the tape, it generates a sound pulse—hence the telltale screech.
DOI: Physical Review E, 2026. 10.1103/p19h-9ysx (About DOIs).
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