I was moving a drinking glass from the kitchen counter to the dishwasher. I barely nicked the edge of the granite countertop, and the glass literally exploded. This is what we collected. You can see that is is truly shattered, not your ordinary glass breaking. Any theories?

 

You must have seen or heard of the singing wine glass trick.
If you wet the tip of your finger and run it on the edge of the wine glass, it will excite the glass at a resonant frequency.
This could cause the wine glass to shatter. Perhaps hitting the wine glass triggered it to vibrate at its resonant frequency causing it to shatter to pieces.

 

Glass shatters like that when it is not, or improperly, annealed.

The outside cooling below the vitrification point before the inside sets up sometimes extreme internal stresses that are released when the glass is broken.

If you use polarized light, you can see the stress.

 

Hi Bob,
A few weeks ago I dropped a moulded glass light fitting on a carpeted wooden floor from a height of about 18 inches, it exploded in to a hundred pieces.

I suspect that the glass fitting had not been correctly annealed after the molten moulding process and was full of heat stress.

E

 

Oh, and look into Prince Rupert’s Drops for an extreme case. The propagation of the fracturing is incredibly fast.

 

You must have seen or heard of the singing wine glass trick.
If you wet the tip of your finger and run it on the edge of the wine glass, it will excite the glass at a resonant frequency.
This could cause the wine glass to shatter. Perhaps hitting the wine glass triggered it to vibrate at its resonant frequency causing it to shatter to pieces.

View attachment 299683

Not to mention singers who allegedly shatter a glass. I thought of exciting a resonance as a possibility.

 

Glass shatters like that when it is not, or improperly, annealed.

The outside cooling below the vitrification point before the inside sets up sometimes extreme internal stresses that are released when the glass is broken.

If you use polarized light, you can see the stress.

Ah, that makes sense. Just needed a minor shock to relieve all that stress.

 

Back in the late 1970s, I worked at a sheet glass-making factory used in window panes. During a particular cold winter day, the natural gas supply faltered.
There was a furnace with over a ton of molten glass, which had to be poured on an open container while it was still a liquid. The container was swiftly towed to the parking lot which had been hastily vacated.
The container was allowed to solidify overnight. Next morning someone with a rifle climbed into a roof perhaps 300 yards away and shot into the now solid lump of glass.
The explosion sounded like a bomb going off, and the thick-walled steel container was shattered. The whole parking lot and an adjacent street were filled with jagged glass particles. Some nearby trees were shredded, like being hit with a fragmentation bomb. Which it was.

This was almost 50 years ago and I still see any large glass objects with distrust.

 

The explosion sounded like a bomb going off, and the thick-walled steel container was shattered

Wow! Lends credence to the lack of annealing theory.

 

Oh, and look into Prince Rupert’s Drops for an extreme case. The propagation of the fracturing is incredibly fast.

Have you ever made them? You can hit the head end with a hammer and it won’t break, but if you break the tip off the tail, the whole thing explodes and turns into a pile of dust.
https://www.academia.edu/7703493/The_Prince_and_the_Popper_The_Mystery_of_Prince_Rupert_s_Drops

 

Have you ever made them? You can hit the head end with a hammer and it won’t break, but if you break the tip off the tail, the whole thing explodes and turns into a pile of dust.
https://www.academia.edu/7703493/The_Prince_and_the_Popper_The_Mystery_of_Prince_Rupert_s_Drops

I played with them a bit when I was working at the science museum. We were considering an exhibit or live session. It was never built while I was there, I don’t know if it ever was.

The Hydraulic Press Channel has several videos featuring them, here’s one of the latest. It may not be the best but it should have the best high speed footage:

 

Tempered glass, which is deliberately cooled in a manner that the stress increases its strength will, of course, break in a many small pieces if it experiences even a small scratch or stress beyond its breaking point.
I had a patio table with a glass top outside in the open, when we had a small hail storm one day.
The next day I discovered a pile of glass below the table with no piece larger that a couple cm.
Apparently the table top was tempered glass, and there was a hail stone big enough to cause it to shatter.

 

Hi,

I second (or third) the internal stress explanation.

There are different phenomena we don't usually see but are ever present in objects of various types.
Different forces that we don't usually see are present in many things and they play a part in how the object is used.

Along with the internal stress phenomenon we also see micro movements, which over time, cause an extreme change in the objects durability. A good example might be when you want to rip a straight edge in a piece of paper or light cardboard. If you fold it over and then fold it over the other way, then back again and again, it gets weaker and weaker, until it gets easy to rip along that fairly straight line. Same with a piece of solid wire.
Making a sword is interesting too, or a knife, where you pound the metal over and over again forcing it to get denser and thus keep a sharp edge better.

How these things are discovered I think is by pure serendipity, probably because it's hard to look for something or some property you don't know is there yet and have no idea that you even should be looking for it. This might be the folly of new inventions.

 

My dad had a Morris Oxford station wagon. One day he was repairing the wood trim on the rear window with a hammer and nails.
A couple taps later, the glass was shattered into a zillion pieces.

 

Regarding singers shattering wine glasses.....

A few years back, I was asked by an advertising friend to help him develop a "Live or Memorex" type exhibit to celebrate a new exhibit at the Tacoma Museum of Glass.

My partner and I did some research and other people had done it before, including the TV program Myth Busters. The common method was using a Peavy 44 public address system horn driver and a power amp. It didn't seem too difficult.....



We located a supply of used Peavy 44s for as I recall 50 bucks a piece (better get two, just to be safe), and I wired up a sine generator controlled by a rotary encoder. A case of cheap Costco wine glasses, ear muffs and safety goggles and we were ready to start testing.

If you put a plastic drinking straw in a wine glass, it will start dancing around as you adjust the oscillator to the glass's resonant frequency and then you just increase the amplitude until....wait for it....the straw is really dancing around....almost....just a little more..... POOF.

Poof? A wine glass goes poof? No. The 50 buck Peavy driver goes poof! With a cloud of smoke!

Turns out that cheap wine glasses are nearly impossible to shatter. As are not-so-cheap wine glasses. Recognizing that people put their wine glasses in the dishwasher, great strides have been made to make them shatter resistant.

Long story short, after exhausting the supply of cheap Peavy drivers, we found some $25 a stem wine glasses that would reliably shatter without blowing up the Peavy drivers. Just barely.

They never managed to get singing to break a glass, but for a nice donation to the museum, people could tune the oscillator and make a glass explode.

 

A few pictures....

 

I was moving a drinking glass from the kitchen counter to the dishwasher. I barely nicked the edge of the granite countertop, and the glass literally exploded. This is what we collected. You can see that is is truly shattered, not your ordinary glass breaking. Any theories?



View attachment 299682

It was granite, right. That's a very hard surface.

 

It was granite, right. That's a very hard surface.

Agreed, if we tip a glass over on the counter it almost certain to break into several large pieces. It is how it broke that was remarkable. It exploded with a loud pop (not glass breaking sound) and glass flew in all directions. Wish I had a video. And I really just nicked the edge of the counter, not a blow you would expect to break it.

 

Your very observant.

 

Regarding singers shattering wine glasses.....

A few years back, I was asked by an advertising friend to help him develop a "Live or Memorex" type exhibit to celebrate a new exhibit at the Tacoma Museum of Glass.

My partner and I did some research and other people had done it before, including the TV program Myth Busters. The common method was using a Peavy 44 public address system horn driver and a power amp. It didn't seem too difficult.....

View attachment 299926View attachment 299927

We located a supply of used Peavy 44s for as I recall 50 bucks a piece (better get two, just to be safe), and I wired up a sine generator controlled by a rotary encoder. A case of cheap Costco wine glasses, ear muffs and safety goggles and we were ready to start testing.

If you put a plastic drinking straw in a wine glass, it will start dancing around as you adjust the oscillator to the glass's resonant frequency and then you just increase the amplitude until....wait for it....the straw is really dancing around....almost....just a little more..... POOF.

Poof? A wine glass goes poof? No. The 50 buck Peavy driver goes poof! With a cloud of smoke!

Turns out that cheap wine glasses are nearly impossible to shatter. As are not-so-cheap wine glasses. Recognizing that people put their wine glasses in the dishwasher, great strides have been made to make them shatter resistant.

Long story short, after exhausting the supply of cheap Peavy drivers, we found some $25 a stem wine glasses that would reliably shatter without blowing up the Peavy drivers. Just barely.

They never managed to get singing to break a glass, but for a nice donation to the museum, people could tune the oscillator and make a glass explode.

Hello,

That's very interesting, but why didn't you guys watch out for how much power you were applying to the horns vs how much they were rated for. Could have saved you a lot of moola.
I played in a few rock bands in the past and one time during a concert my 15 inch speaker (guitar amplifier) blew out. We had to stop the whole show. That was nuts. Again, it was too much power. I had rewired the amplifier to provide more power and that was the main issue as the speaker could not handle the increase in power.

I noticed your member's name because there is an actor who played the part of a bomb making expert on one episode of Columbo whose name is John Chandler. The episode was titled "Publish or Perish". That's one of my favorite episodes and there is some interesting background info about the actor that played the really bad guy. Briefly, in the episode, he got drunk on purpose and smashed his car so he would get put in jail for the night to act as an alibi for a murder he had the bomb guy commit for him. In real life, the actor got drunk and was smoking in bed and he fell asleep. His bed caught on fire and he died. That was a shame he was a good actor.

The moral of both stories is, don't smoke in bed and do not apply too much power to your speakers.