Re: [math-fun] Fabricating a glass/crystal sphere circa 1500
Henry got that right — in fact, something quite interesting happens, as Wikipedia says: ----- 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 the tail end is even slightly damaged. In nature, similar structures are produced under certain conditions in volcanic lava. ----- more at https://en.wikipedia.org/wiki/Prince_Rupert's_Drop. —Dan Henry Baker wrote: ----- If you don't remove the air in such a column, you're likely to get shot that is more raindrop-shaped than sphere-shaped. ----- I wrote: ----- ... I'd try dropping molten glass some distance through the air to make it form into a sphere, and have it land in water to make it rigid. —Dan Henry Baker wrote: ----- It's the year 1500, and some wealthy patron wants a transparent glass and/or rock crystal sphere perhaps 6-8" in diameter. How would you fabricate it? ... ... ----- -----
On Oct 22, 2017, at 2:57 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Henry got that right — in fact, something quite interesting happens, as Wikipedia says:
----- 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 the tail end is even slightly damaged. In nature, similar structures are produced under certain conditions in volcanic lava. ——
By a strange coincidence I was at the Corning Museum of Glass yesterday, where a Prince Rupert Drop was featured in a hands-on demo of glass toughness. I tried, unsuccessfully, to fracture it with the hefty steel piston in the exhibit.
more at https://en.wikipedia.org/wiki/Prince_Rupert's_Drop.
—Dan
Henry Baker wrote: ----- If you don't remove the air in such a column, you're likely to get shot that is more raindrop-shaped than sphere-shaped. -----
That’s not actually what happens. When moving through the atmosphere at terminal velocity, there is reduced pressure at the “equator” of the drop causing it to bulge as an oblate spheroid (assuming a small drop for which Stokes flow applies). The “rain-drop” = “tear-drop” shape is a non-equilibrium effect, such as when a water drop separates from a faucet or, as with Prince Rupert, is suddenly cooled in a colder liquid. -Veit
participants (2)
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Dan Asimov -
Veit Elser