Shattered glass table mystery

Here's a good riddle for you guys: Why did our glass table shatter this morning?

Sometime this morning our glass-topped table just shattered. It's tempered glass inside a steel frame. The table is in a screen room, so it's not like an animal jumped on it. There was nothing on the table aside from a pot holder. It's been a while since we have used the table, too.

Our backyard is also very shady, so I doubt it was suddenly hit by a strong beam of sunlight that caused a rapid temperature change. It was a bit cool this morning, but it was colder last week.

The table is a couple of years old. The original top shattered a few years ago (similar conditions) and the replacement included new glass and a new frame.

So, any ideas? And since I'd rather not clean up a pile of glass every few years, what makes a better alternative?

CTE mismatch between glass & steel? replace with diamond plate.

Kendall

Tempered glass is weird stuff. My guess is if you look at the frame, there is something that has been rubbing the edge of the glass. You can pound the surface with a hammer and it won't break, but just touch the edge hard and it'll explode. Movement from expansion and contraction probably damaged the edge over time. Tempered glass has an amazing amount of surface tension. The tempering process actually compresses the interior of the glass under the surface. Like a balloon, if you damage that surface, it pops.

Use to be a glazer and tempered glass can shatter for no real reason. The glass just lets go.

Small bit of rust inside the steel frame, slowly growing & pushing on it?

If it matters, the replacement glass came with a new frame. The whole table top is just a few years old.

Toyman01 wrote: Tempered glass is weird stuff. My guess is if you look at the frame, there is something that has been rubbing the edge of the glass. You can pound the surface with a hammer and it won't break, but just touch the edge hard and it'll explode. Movement from expansion and contraction probably damaged the edge over time. Tempered glass has an amazing amount of surface tension. The tempering process actually compresses the interior of the glass under the surface. Like a balloon, if you damage that surface, it pops.

Is that why the piece of spark plug will explode a car window?

My wife just corrected me. The first table shattered after a year--the top was replaced under warranty. This top is about 8 years old. Wacky, huh? And who wants to help clean up a bunch of glass?

Um. Is there a hole in your roof?

http://www.thebostonchannel.com/r/29899519/detail.html

In reply to e_pie:

Yep. I have watched a 250 pound guy pound a truck window with a piece of 2" pipe and not break it. But a auto center punch will pop it with just a click.

I just found out that oven safe dosent mean pizza oven safe. The casserole dish shattered unexpectedly. Did you have the glass in the pizza oven ?

Tempered glass is good to about 400 degrees. Pyrex brand stuff is usually a ceramic based glass. It's stable to about 1500.

I had one shatter a few years ago and was quite mystified by it. Glad you posted this.

By the way, the pile of glass hasn't cleaned itself up yet. Last time I remember it filling a good portion of a 5-gallon bucket.

Toyman01 wrote: Tempered glass is good to about 400 degrees. Pyrex brand stuff is usually a ceramic based glass. It's stable to about 1500.

The Pyrex statement was true until about a decade ago. Pyrex changed the type of glass that they use for their consumer products from borosilicate glass to soda lime glass. From what I gather, the soda lime stuff is cheaper to manufacture. However, the lab glass (beakers, graduated cylinders, etc..) is still made from borosilicate, and can take the direct heat. Lab beakers and such can take just about anything that you can throw at them, but they're not cheap.

I know this because a few years back, I heated a glass Pyrex measuring cup on the stove, and it shattered as soon as I set it on the counter. When I was growing up, we would put all of our Pyrex stuff on the stove without any ill effects. We even had a glass saucepan that we used a few times a week to make iced tea for ~20 years.

If hoodlum toddlers and roaming animals can be ruled out as causes of shattering glass, my vote goes for a ticked off ghost. Hear any unusual noises around the place lately?

Were the mythbusters firing a cannon nearby?

Vent window in the '64 Fairlane did that while we were cruising through Missouri lo, these many years ago. Thought we were being fired upon.

ncjay wrote: If hoodlum toddlers and roaming animals can be ruled out as causes of shattering glass, my vote goes for a ticked off ghost. Hear any unusual noises around the place lately?

The biggest thing that could have been in that room was a lizard. Dogs were inside the house, too. Ghosts? Maybe.

ncjay wrote: If hoodlum toddlers and roaming animals can be ruled out as causes of shattering glass, my vote goes for a ticked off ghost. Hear any unusual noises around the place lately?

My vote

My guess is the metal frame table is expanding & contracting with the temperature changes, and the slightest blemish on the outer rim of the glass is a stress fracture waiting to happen. That's why most glass tables are free floating (no outer support), or if they are, it's a wood frame. Get a replacement glass that is slightly smaller (fractions of an inch) than the inner dimensions of the frame.

Had a computer desk crack due to cold being next to a window. It had a computer on it blowing hot air at it. Although in weather with an unstable temperature, I've seen parts of glass tables seemingly randomly shatter.

Glass, especially tempered, is not really solid, but a very viscous liquid - hence why old houses have windows with waves in the glass. Also, tempered glass has to be "Cooled" at a very specific rate once the silica sand its composed of has been molten, and a sheet formed. If it doesnt cool at just the right rate, and evenly across the sheet, it will develop risers in the grain structure - these risers will continue to "cure" for a lack of a better term, indefinitely, at a different rate than the rest of the sheet. Over a long enough timeline, the survival rate of everything is zero...it would appear that tables are no exception.

We do a bunch of Glass art , The media we use is Tempered glass , vinyl and window film . . Cover both sides of new glass with clear hurricane film ........ Check out this www.artofmurf.com

Will trade glass cleanup for tickets to the 24, though we won't be in the area until the 24...