# Prince Rupert's Ring **URL:** \ **Category:** Factual Questions\ **Created:** [January 3, 2018, 1:36pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794 "2018-01-03T13:36:40Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 3, 2018, 1:36pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794/1 "2018-01-03T13:36:40Z")
Is it possible to make a toughened glass ring with Price Rupert’s Drop-like properties by forming a torus of hot glass then dropping the whole thing into water? I know the glass for PRDs is normally molten to a liquid state, but I don’t think it would be very hard to contrive a device that extrudes and shapes glass into a ring shape whilst keeping it hot enough. Would this result in a PRD with no ‘tail’ and therefore extra durability? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 3, 2018, 2:13pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794/2 "2018-01-03T14:13:53Z")
As I understand it, tempered glass always ends up with a weak point somewhere. When the shape includes a point, that’s usually where the weak point is. But even if it doesn’t, there will still be a weak spot; it’s just harder to tell where it is. And I misread the thread title at first as being about a different prince with a ring associated with his name. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [January 3, 2018, 2:31pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794/3 "2018-01-03T14:31:25Z")
If you just want a toughened glass ring, it may be possible: > [@https://en.wikipedia.org/wiki/Toughened\_glass#Manufacturing](#): > > Chemical toughening results in increased toughness compared with thermal toughening and can be applied to glass objects of complex shapes. I’m not sure if a perfectly symmetrical torus would have stability issues or not, or how tough it would be, but there appears to be no barrier to creating one. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 3, 2018, 2:43pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794/4 "2018-01-03T14:43:48Z")
> [@Chronos](#): > > As I understand it, tempered glass always ends up with a weak point somewhere. When the shape includes a point, that’s usually where the weak point is. But even if it doesn’t, there will still be a weak spot; it’s just harder to tell where it is. I’m not sure if the ‘weak spot somewhere’ is an essential part of the phenomenon (like the stress-balancing version of Hairy Ball Theorem) or if it’s just an accident of the way things are typically, but not compulsorily made. For example a sphere of molten glass cooled rapidly and evenly across its entire surface area should - I think - result in the whole of the inside volume being under tension, pulling the outside surface inward, rendering the entire surface strong (the ‘weak point’ here being inaccessible inside the sphere). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 3, 2018, 3:12pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794/5 "2018-01-03T15:12:33Z")
I’m not sure it’s possible to cool it uniformly enough to do that, though. You can’t just drop it into a bucket of water, for instance, because there’s always going to be some spot that enters the water first and some spot that’s last. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 3, 2018, 3:32pm UTC](https://boards.straightdope.com/t/prince-ruperts-ring/805794/6 "2018-01-03T15:32:47Z")
Tempered Glass windows are made all the time without there being any “hairy Tennis Ball” weak points: [Tempered glass - Wikipedia](https://en.wikipedia.org/wiki/Toughened_glass) The reason that Prince Rupert’s Drops have that shape is that they’re easy to make that way – you take the glob of molten glass you’re working with and drop it into a bucket of water. The skin immediately cools and you get that characteristic temper over the surface, making it tough and capable of withstanding surprising pounding – except I that vulnerable tail. In principle it ought to be possible to get a torus to temper evenly all over, but I have no idea how you’d go about manufacturing one as a practical matter. The OP should’ve included some links – Prince Rupert’s Drops are a fascinating yet not very well-known phenomenon: > **[Prince Rupert's drop](https://en.wikipedia.org/wiki/Prince_Rupert%27s_Drop)** > > Prince Rupert's drops (also known as Dutch or Batavian tears) are toughened glass beads created by dripping molten glass into cold water, which causes it to solidify into a tadpole-shaped droplet with a long, thin tail. These droplets are characterized internally by very high residual stresses, which give rise to counter-intuitive properties, such as the ability to withstand a blow from a hammer or a bullet on the bulbous end without breaking, while exhibiting explosive disintegration if th The d... High Speed video of the drops: [![](https://img.youtube.com/vi/xe-f4gokRBs/hqdefault.jpg "Mystery of Prince Rupert's Drop at 130,000 fps - Smarter Every Day 86") ](https://www.youtube.com/watch?v=xe-f4gokRBs)