How does glass break?

In what sense are you using the word "remember"?

"or it had a point I do not see?"

Do you mean, "is there an invisible fracture 'starting point'"?

Do not be afraid to be lengthy in your description of what's going on. The more information - the better explanation - the more likely we are to be able to help.

There are a number of things that could be going on here, but your information is sketchy.

Mike

Mike, yes I do mean an invisible fracture starting point.

There could be many scenarios on how a vase would break, I believe...

From the brittle nature of glass, I know that an invisible fracture could initiate a star fracture mode that spreads throughout the vase. This given that there are other invisible fractures that make a bridge and the vase collpases. This for me would require a large compressive force from top to bottom when exerted with the hands. No matter how strong a person is.

I have observed and experienced that when loading my dishwashing and holding a wine glass it suddenly will break in large pieces, one or two...not in multiple pieces. In an martini shaker...could it break in many small pieces when being held by hand with ice and liquids in it? The glass to break in many pieces would require: many internal impurities??? and a large force axially, or , an external initiating impact, or , many external impingements as if marbels would have dented the external surface, or, multiple side ways forces...by hand....

HOW COULD A VASEA BREAK IN MULTIPLE PIECES IF i WAS HOLDING IT TOP AND BOTTOM AND IT WOULD JUST BREAK?

I believe I need and external condition to initiate a multiple break...

First, google it. Who knows?, you might just get something like:

http://www.coursework.info/A2_and_A-Level/Design_and_Technology/How_Does_Glass_Break_L44048.html

Then, I remember being told once, that yes, there are minute weak molecular inconsistencies in glass, because glass is not considered a lattice type of solid, but a "Room-Temperature Super-Cooled Liquid"

"Super-Cooled Liquid" means it is being held together under some high inner-tension, an kind of inner-pressure, waiting to go outwards and explode, at the "slightest" disturbance.

So yes, there might just be cracks invisible to the naked eye there.

Then, given a sound, vibration, harmony, overtone, a rub, some oriented pressure, or a change of temperature, with or without the presence of your mentioned liquid, it will start a crack into a fissure.

The fissure will extend through the glass, supersonic, creating a shockwave, sometimes making opposite cracks meet, not unlike the trail of progression typical to lightning, of all things.

Don't take my word for it, this is just about what I was told.

A rapid change in temperature, like picking up a hot glass, would also cause fractures and cause the glass to break due to micrpscopic air pockets in the glass changing temperatures rapidly, wouldn't it?

...micrpscopic air pockets in the glass...

The tiny bubbles you might see in the glass, were trapped during the making of the glass, not later, when the glass was re-heated.

The glass' inner tension, will resist the trapped gas inside the bubbles, which is trying to expand because of the heat.

If you have ever been in a glass factory - you would see that as soon as the caster completes a glass object - picture tube, perfume bottle, beer bottle, what ever, it goes straight through a temper furnace to relieve the internal stress setup by the rapid cooling.

If the glass furnace has to be drained the glass globules that are formed can explode without beng disturbed just from the residual stresses.

Two important points about glass

1. It does not conduct heat well

2. It is not very flexible (brittle)

Any temperature change on glass must be done evenly on the whole mass, otherwise the stresses built up by the expanding or contracting glass will overcome the flexibility strength of the surrounding glass and cause it to break, shatter, or expode

Also most wine glasses, have a small bump on the top ridge which is a result of the manufacturing process. This small imperfection in thickness is enought to cause small temperature differences and high stress when the glass is heated or cooled. This 'weak' spot, will usually have a semicircle of stress around the bump and is the most likely spot to break.

I have had different occurances when glass shatters in my hand. Temperature in these cases was not an issue,(they had been in my sink at room temperature.) The first glass that shattered was a Pyrex dish. Is this normal?