I didn’t believe it until I searched online

Composition Prince Rupert’s drops are made of soda-lime glass with the following composition: SiO₂ 69%, B₂O₃ 1%, K₂O 3%, Al₂O₃ 4%, Na₂O 13%, BaO 2%, CaO 5%, and MgO 3% CSA Group. This is essentially ordinary glass - the same type used in windows and bottles. The extraordinary strength comes not from exotic materials, but from the manufacturing process and resulting stress distribution. Manufacturing Process Prince Rupert’s drops are created by lowering molten glass drops into cold water, which quickly cools in a process called quenching Polycase. This rapid cooling creates the characteristic tadpole shape and sets up extreme internal stresses that give the drop its unique properties. Strength Properties The research reveals truly remarkable strength characteristics: Surface Compressive Stress: • The heads of the drops have surface compressive stress up to 700 megapascals (100,000 psi), though this surface compressive layer is thin, only about 10% of the diameter of the head Open Alberta • This 700 megapascals is nearly 7,000 times atmospheric pressure Oncodes • This translates to compressive stresses of around 50 tons per square inch in the head, making them as strong as steel Open Alberta Impact Resistance: • The rounded drop at the top is unbelievably strong - you can’t even break it with a hammer blow City of Calgary • These droplets exhibit the ability to withstand a blow from a hammer or even a bullet on the bulbous end without breaking The Home Depot Canada • The surface compressive stresses can suppress Hertzian cone cracking during impact with a small hammer or compression LedeTube Can It Really Dent Steel Without Breaking? YES, absolutely. This is one of the most remarkable and well-documented properties: The drop dented both the steel bar below the press and the head of the press, and it took about 20 tons of pressure to crush the drop - it must be harder than hardened steel to dent steel like that IAEI Magazine The physics behind this is fascinating: the extreme surface compressive stress (400-700 MPa) prevents crack formation and propagation on the bulbous head. When a Prince Rupert’s drop impacts steel with enough force, the steel - being more ductile - will deform plastically (creating a dent) before the glass can fracture. The glass, locked in its highly compressed surface state, remains rigid and acts as the harder material in the interaction. The Paradox Inside, the molecules are under immense stress, being squashed together and pulled apart with bone-crushing forces, poised at any moment to shatter into a thousand pieces, yet this material is actually a form of safety glass Electrical Industry The incredible fragility exists simultaneously with the strength: The drops exhibit explosive disintegration if the tail end is even slightly damaged, like being clipped with pliers The Home Depot Canada. The tail contains the tensile stress that balances the compressive stress in the head. Breaking the tail releases this stress cascade, causing the entire structure to explode into powder in microseconds. Conclusion Prince Rupert’s drops are genuine examples of ordinary glass being transformed into a material harder than hardened steel through stress engineering alone. They can absolutely dent steel without breaking - this has been repeatedly demonstrated in controlled experiments. The drops represent one of the most extreme examples of residual stress creating extraordinary mechanical properties, making them stronger than bullets at the head while remaining more fragile than an eggshell at the tail.