https://www.popularmechanics.com/science/a40008994/why-the-prince-ruperts-drop-is-so-strong/ SearchSearchClose --------------------------------------------------------------------- * Pop Mech Pro * Subscribe * Home and DIY * Power Tools * Cars * Technology * Military * Science * Adventure * Sci-Fi * Airplanes * Space * Gifts * Deals * Visual Stories * Promotions * Shop * Follow * Get Our Newsletter * My Bookmarks Opt-Out IconYour Privacy Choices Privacy NoticeTerms Of Use Skip to Content Logo * News * Science * Military * Home * Gear Reviews * Pop Mech Pro Subscribe sign in Search Search Search[ ] 7,000-Year-Old Mummies3 Futuristic InventionsBest Pressure WashersA Guide to LeatherNintendo Switch 2 Launch 1. Science 2. Pop Mech Exclusives 3. Why 'Prince Rupert's Drop' Glass Is Strong Enough to Shatter a Bullet Why 'Prince Rupert's Drop' Glass Is Strong Enough to Shatter a Bullet Don't be fooled by this delicate drop of glass. It's actually really hard to destroy. By Manasee WaghUpdated: Aug 04, 2023 12:29 PM EDT bookmarksSave Article youtubeView full post on Youtube * For glassmakers, a "Prince Rupert's drop" is simple to make but strong enough to shatter a bullet. * The way a drop of hot glass cools in water is the secret to its strength. * The physics that make the drop so tough have applications for thin, yet strong, protective surfaces. --------------------------------------------------------------------- Formed of a glass teardrop that elongates into a skinny tail, a "Prince Rupert's drop" looks like a delicate, clear tadpole. It's easy enough to snap the tail, but the rounded drop at the top itself? It's unbelievably strong. You can't even break it with a hammer blow. When a glassmaker drips molten glass into cold water, it freezes into a bead with an extra long tail. Like Sauron's One Ring, you can't break it with a heavy blow from something as strong as an axe. You actually need the speed and force of a bullet to shatter it. The crazy part is that even a bullet can break apart when it hits the drop. (Check out the video at the top of the story from SmarterEveryDay.) The Science Behind the Magic When the bullet grazes the bulb of the drop itself, you can see a line of white take off from the tail and race down the drop. This is a traveling shockwave. Two factors--compressive strength built into the drop during its formation and the residual stress of the impact--cause the near-instantaneous destruction of the smooth glass. A fraction of a second later--a stunning sequence visible at 100,000 frames per second--the entire object vaporizes into sparkly smoke. Rather than exploding in all directions, the glass shatters in place because the compression and tension are released all at once. The bullet itself shatters due to the glass head releasing its compressive force. Bullet fragments fly off in a wide array, embedding themselves into the wall behind the setup. Glass melts between 2,552 degrees and 2,912 degrees Fahrenheit. When a glassmaker drops a molten glass bead into a tank of water, its surface cools rapidly, quickly forming a hardened shell around the liquid interior, similar to an egg white cooking faster than the yolk inside. The molten glass inside continues to cool and retract, pulling the outer layer inward as much as possible. The inner core becomes tightly compressed, which generates an incredible amount of tension in the drop. This is the compressive force that binds together the layers, forming a strong shock absorber made of glass. Surface tension helps hold the drop together. Practical Applications youtubeView full post on Youtube Prince Rupert's drops may be fun to break, but they also present an opportunity to strengthen useful objects--for example, a special type of tough glass could cover our mobile devices. The MythBusters pair in the Corning video above demonstrate Gorilla Glass, a thin sheet of seemingly delicate glass that's actually super strong. Corning developed the glass using the same principles of compressive strength that make the Prince Rupert's drop so hard to break. The glass is made to be tough through a process called ion exchange. During manufacturing, small ion particles form at the surface. These are usually electrically-charged sodium atoms. To toughen the surface, the glass is dipped into a salt solution, causing larger, potassium ions to swap places at the surface of the glass with the smaller ions. These larger particles generate pressure on the interior parts of the glass sheet, compressing it tightly. Unlike the Prince Rupert's drop, Gorilla Glass can be modified during manufacture to control the tension inside the glass, so that it doesn't compete too much with the compressive force. With the forces in balance, the glass gains strength. It's still not unbreakable, but it could add a protective layer to objects like cell phones in the future. If you drop your phone on the pavement, you can breathe easy if it's wearing a thin layer of Gorilla Glass. Here's an extra video with more satisfying smithereens of Prince Rupert's drops. youtubeView full post on Youtube More out-of-this-world stories * [13877095484-5fe7]Why Radioactive Uranium Glass Glows Bright Green * [abstract-backgro]Scientists Create Sci-Fi Metamaterial Using 4D * [lta-research-pat]The Electric Airship Revolution Is Almost Here Headshot of Manasee Wagh Manasee Wagh Features Editor Before joining Popular Mechanics in 2022, Manasee Wagh worked as a science journalist, a newspaper reporter, a technical writer, and an engineer. She has a bachelor's degree in computer engineering and a master's degree in journalism. Her favorite stories are about the discoveries that unearth even deeper mysteries, and she enjoys helping people understand the science behind the remarkable world we live in. She lives in the Northeast with her two favorite people and one curious, feisty feline, but always seeks to combine her love of food, nature, and travel into memorable journeys away from home. 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