# How often does glass break?



## 4BigFish (Jan 6, 2014)

I just had my door glass replaced in my 6 week old Hearthstone Manchester at a local glass shop.  The guy doing the replacing said I was his 3rd stove glass replacement in the last 2 days and the 6th in the last week.
(the story is in another thread, I just didn't want to wait for warranty replacement due to weather)

I had a Treemont for 24 years, never a break.

I'm curious, how many of us have experienced a glass break and what were the circumstances? and what stove model?
In my case this was my first one,  I was just starting to light a fire and log shifted, hitting the glass, crack.


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## mellow (Jan 6, 2014)

I broke mine while putting in new door/window gaskets,  wasn't burning at the time.  Other than that I have never had a cracked window while burning.   I think you can chalk it up to these bigger windows that everyone wants, more surface area for a log to roll on to cracking it.


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## begreen (Jan 6, 2014)

Hopefully never, though E/W loaders are more prone to log roll than a N/S loader. Then again, how often will you hit a deer? Hopefully never, but then again, chit happens especially if you live in an area with deer overpopulation.


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## Paulywalnut (Jan 6, 2014)

I split everything. Nothing round over 3 or 4 inches in the stove. I know a pie shape can shift but it's less likely.
Sorry to hear that about your glass. Just a tap? maybe if it's real hot. That's a real puzzle.


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## Oldhippie (Jan 6, 2014)

The andirons seem to do a pretty good job protecting the glass in both my EW stoves. One being a side load and the other being a top loader.


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## GeHmTS (Jan 6, 2014)

I'm not sure often glass breaks, yet it will most definitely break if you touch it with something cold while it's hot. I haven't broke my glass yet, but I do have a spare ready in case I do.


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## EatenByLimestone (Jan 7, 2014)

I haven't broken one... yet.  I had to replace a piece of glass on my first stove when I bought it.  There was a piece of steel in it's place.


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## firefighterjake (Jan 7, 2014)

GeHmTS said:


> I'm not sure often glass breaks, yet it will most definitely break if you touch it with something cold while it's hot. I haven't broke my glass yet, but I do have a spare ready in case I do.


 

Are you sure about the temp thing . . .

http://www.woodstove-fireplaceglass.com/Neoceram.html

Pretty sure there is a video out there that has been mentioned where a person heats up the neocream (or pyroceram) and then drops a chunk of ice or snowball on it to show that it is thermal resistant.


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## Hickorynut (Jan 7, 2014)

I wipe my hot door glass all the time with a paper towel wet with cold water, always thought the glass was thermal resistant.  If it can take the heat then..................


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## Highbeam (Jan 7, 2014)

How often does glass break?

Only as often as YOU break it. I don't know of anybody that ever had glass just suddenly break on its own. So this is like trying to prevent a speeding ticket, you are in complete control and it is completely preventable unlike a deer impact which has an element of chance.

Fortunately I have never owned a stove that required E/W loading from the front where you are supposed to chuck the last few logs up on the pile and hope they stay. I would suspect that folks with those stoves are more likely to break their glass since setting those logs securely is more difficult.


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## BrotherBart (Jan 7, 2014)

http://www.fireglass.com/product-testing/


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## andybaker (Jan 7, 2014)

I've had, on several occasions, had a log roll right onto the glass and burn there.  Not me loading but someone from the family that doesn't like getting their hands close to the coals.  Anyway, when I've gotten home a few times I'll see where the log lay rested against the glass and it completely burns down there.  No damage to the glass.  Cleans right off next time I do a cleaning.  I've been impressed with how strong this new glass is.  Mine is a pyroceram type glass.  You say you went to your local glass shop and got a replacement.  Do they carry the newer stove type glass at a shop like that?


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## GeHmTS (Jan 7, 2014)

firefighterjake said:


> Are you sure about the temp thing . . .
> 
> http://www.woodstove-fireplaceglass.com/Neoceram.html
> 
> Pretty sure there is a video out there that has been mentioned where a person heats up the neocream (or pyroceram) and then drops a chunk of ice or snowball on it to show that it is thermal resistant.


I pretty sure glass is brittle and that putting something cold on a hot brittle material is never a good idea.


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## firefighterjake (Jan 7, 2014)

GeHmTS said:


> I pretty sure glass is brittle and that putting something cold on a hot brittle material is never a good idea.



Glass yes . . . pyroceram and neoceram are not glass -- ceramics . . . hence their unique thermal properties.


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## Dustin92 (Jan 7, 2014)

I have had logs/splits fall against the glass and burn there even, and I have used the doors to jam in a split that is just "a bit" too long (not recommended). I have had a wet dog shake himself off in front of the stove, leaving only waterspots on the glass. I am guilty of cleaning the glass while the stove is hot. I have never cracked the glass or ever heard of stove glass just cracking. Our stove has small (7"or so) windows, so less chance I guess, but also less fire view.


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## McKeznak (Jan 7, 2014)

I've run my 'glass'_ (it's a clear ceramic or something)_ through the ringer learning how to operate my stoves, high temps, low temps, gasket replacements, even accidentally spilling water from a vaporizer thing down the front of the hot glass and nothing has ever cracked. Quite impressive in fact.

Although on my first walk through when buying this house the 'glass' in the F2400 was shattered... the scary part is they were still burning in it. Anyways I asked them what happened and they mentioned something about the poker but I never got a straight answer.


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## lazeedan (Jan 7, 2014)

I Have had rounds and splits shift. They burn laying against the glass. I load E/W. So for no issues. Knock on wood.


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## McKeznak (Jan 7, 2014)

lazeedan said:


> I Have had rounds and splits shift. They burn laying against the glass. I load E/W. So for no issues. Knock on wood.



You can knock on the wood, just not on the glass


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## begreen (Jan 7, 2014)

The most common cause of glass breakage is from closing the door against a log end and from hitting it with a stove tool.


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## MikoDel (Jan 7, 2014)

Highbeam said:


> How often does glass break?
> 
> Only as often as YOU break it. I don't know of anybody that ever had glass just suddenly break on its own.



It happened to me, when the coals were right against the glass on one of the doors. Of course it had to be during one of the coldest spells ever for PA, about 15 years back. We didn't have our stove for about a week!

I was negligent in emptying the ash, but it wasn't because of laziness. I didn't know about Shelby Firewall gloves at the time. We were burning night and day during that weekend and the stove never cooled down enough to grab that pan with any gloves I owned. The coals had built up enough so that they were actually at or above the highest ash fettle. The glass was taking the heat from the burning splits plus the full onslaught of the coals. Don't you know I was looking right at the stove and actually saw it break. The lower cracked piece slipped down and opened up a horizontal, curvy crack about 1/4".  I thank my Angels we were there when it happened. I can't imagine how hot this heater would run in that condition. And I figured out about the gloves shortly ater that.

Tonight is a cold, cold one too. I tied a new eye-to-eye tail, whipped the ends, and tested the length with a VT friction hitch, all by the warmth of this beautiful stove.

Happy Holidays everyone. I know it's silly but I like getting the birthday greetings from the forums.


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## jharkin (Jan 8, 2014)

In spite of the andirons I have had large splits at te top of the load fall against the glass a couple times during burns. Never an issue.  I pulled my windows out to change the gasket last summer and had to really work on some of the clips.  No issue.

The ceramic is tough.


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## billb3 (Jan 8, 2014)

I've had the window in a brand new stove crack on the 4th fire - the first time the glass hit 600 degrees.
Cracked right under a retaining clip and screw.
The retaining  clip screw was likely just over-torqued just a tiny bit too much.
One single straight vertical crack from the top screw to the one on the bottom directly under it.



I've had glass in a jotul 600 crack when a log(s) shifted and rolled to the front
I heard the log roll/shift, didn't hear the glass crack. It made enough noise to look over immediately after it rolled.
Never used the front doors on that stove because it made such a mess unless you cleaned the ashes out anally.
Logs rolled against the replaced glass occasionally with no issue - stress in the glass maybe ?


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## Bluerubi (Jan 8, 2014)

I've had two panes of glass break on their own with my old Jotul firelight 12 in the midst of a burn with nothing bumping or against them. This happened very shortly after I purchased it used and went through my rebuild.  I thought there was something defective with the stove till I noticed that the spring clips that are supposed to hold the glass against the door were replaced by the previous owner with little pieces of steel bar.  When the cast iron expanded as the stove heated there wasn't any way for the glass to move independently of the door, and there would be a loud cracking sound.  Once I put in the factory clips from Jotul it was smooth sailing ever since.  Pretty scary when it happened on full loads though.


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## billb3 (Jan 8, 2014)

Not much evidence for operator abuse in this thread yet.
C'mon stove abusers, speak up !  !  !  !  !
We know you're out there.
Anybody ?


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## Bluerubi (Jan 8, 2014)

billb3 said:


> Not much evidence for operator abuse in this thread yet.
> C'mon stove abusers, speak up !  !  !  !  !
> We know you're out there.
> Anybody ?



Okay.  I also broke a third pane of glass when my poker slipped while pulling a log close to the front.  Busted a hole right through it for yet another $100 bill up the chimney.


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## 4BigFish (Jan 10, 2014)

andybaker said:


> I've had, on several occasions, had a log roll right onto the glass and burn there.  Not me loading but someone from the family that doesn't like getting their hands close to the coals.  Anyway, when I've gotten home a few times I'll see where the log lay rested against the glass and it completely burns down there.  No damage to the glass.  Cleans right off next time I do a cleaning.  I've been impressed with how strong this new glass is.  Mine is a pyroceram type glass.  You say you went to your local glass shop and got a replacement.  Do they carry the newer stove type glass at a shop like that?



The glass shop did carry pyro.  One of the few in the area that does.  The local windshield places didn't have it.  Been burning strong all week. The more I'm using this stove the less I'm liking the large glass because now I am paranoid with every log I place in.  I'm kind of wanting that Tremont back...


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## 4BigFish (Jan 10, 2014)

Highbeam said:


> How often does glass break?
> 
> Only as often as YOU break it. I don't know of anybody that ever had glass just suddenly break on its own. So this is like trying to prevent a speeding ticket, you are in complete control and it is completely preventable unlike a deer impact which has an element of chance.
> 
> Fortunately I have never owned a stove that required E/W loading from the front where you are supposed to chuck the last few logs up on the pile and hope they stay. I would suspect that folks with those stoves are more likely to break their glass since setting those logs securely is more difficult.



I agree "I broke it" but it was a log rolling a half turn. I've had that happen dozens of times on my old Tremont over the years.  The Manchester has a side load door which is why I purchased that model.  It burns great. Puts out good heat, easy to keep stoked an has a nice ash pan.  I keeping looking at that large glass door.  It is fun to watch the fire but its a lot of glass to be careful with...


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## 4BigFish (Jan 10, 2014)

Anyone have the glass break on a Blaze King, King or Princess model?


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## ridemgis (Jan 10, 2014)

Check out this video from Kuma stove:



The ceramic will handle a direct hit without breaking, but it doesn't bend well.  So a log rolling into it will do no harm.  Force the door shut against an oversize split and you are toast.  And no I don't plan to test this on my stove!


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## Highbeam (Jan 10, 2014)

4BigFish said:


> Anyone have the glass break on a Blaze King, King or Princess model?


 
The BKs you mention are very square and designed primarily as north/south burners. As such nothing to worry about.


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## firefighterjake (Jan 10, 2014)

ridemgis said:


> Check out this video from Kuma stove:
> 
> 
> 
> The ceramic will handle a direct hit without breaking, but it doesn't bend well.  So a log rolling into it will do no harm.  Force the door shut against an oversize split and you are toast.  And no I don't plan to test this on my stove!




Great video . . . and it shows what some of us have stated about the durability. That said . . . I must confess that I cringed every time with every hit.


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## ridemgis (Jan 10, 2014)

firefighterjake said:


> . . . I must confess that I cringed every time with every hit.



Me too!  The first time he hit it I about leapt out of my chair!  I wake up in the night thinking that thump I heard was a split falling hard against that huge fragile window.  Actually it's my shift working neighbor slamming his car door at 4am.


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## billb3 (Jan 10, 2014)

4BigFish said:


> The glass shop did carry pyro.  One of the few in the area that does.  The local windshield places didn't have it.  Been burning strong all week. The more I'm using this stove the less I'm liking the large glass because now I am paranoid with every log I place in.  I'm kind of wanting that Tremont back...


Having a second  window break would be like winning Megabucks  a second time.
You've had your once in a lifetime event. Get some sleep.


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## PercivallPotts (Feb 13, 2014)

The reason regular glass and even pyrex glass is sensitive to thermal shock is two fold.  It has a relatively large coefficient of thermal expansion (gets larger as it gets hot and smaller as it gets colder) and it has a relatively low thermal conductivity (does not conduct heat very fast the way metals do).  With these two properties combined, a hot glass that is cooled in a small area by a splash of water or a random snow ball results in cold spot that shrinks and pulls on the surrounding material (tensile strain).  Since the glass does not conduct heat to the cold area very quickly the thermal strain grows much faster than thermal conduction can relieve. 
With the high temps in the burn box of wood stoves this can result in tremendous internal strain.  Since glass is a non-compressible/ stretchable material it can only take a limited amount of strain before it shears / cracks.  Couple that with a retaining clip / screw that is just a bit too tight and hot burn... the metal in the door expands more than the glass resulting in a pressure point (internal strain) on the glass and then the thermal shock puts it over and Wa-La.  A crack runs through it.

Ceramics are not this way, they have virtually zero thermal expansion coefficient therefore the difference in temperature in v. hot area and v.cold area causes very little internal strain.  The transparent ceramic window used in modern wood stoves is quite stable to thermal shock.  (As others have noted)

I did learn something new about how impact resistant they are from that video, THANKS.  I bet it would be a different result if he used a harder object and not a soft 2x4...


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## Dakotas Dad (Feb 14, 2014)

firefighterjake said:


> Great video . . . and it shows what some of us have stated about the durability. That said . . . *I must confess that I cringed every time with every hit.*



Heck, I said a four letter word! and it wasn't "fudge"..


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## DanCorcoran (Feb 14, 2014)

*"How often does glass break?"*

Only once, usually...(sorry, I couldn't resist).


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## begreen (Feb 14, 2014)

Rarely.


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## Hogwildz (Feb 14, 2014)

Ah another reason to love a north to south loading stove. No broken glass, unless you try to close the door against a pc that is too long.
Sorry, just not enough to wish to going back to an old smoke dragon.
Not the stoves fault.


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## BrotherBart (Feb 14, 2014)

My old stove has glass in the doors. 21 years of burning in the house and eight years burning in the backyard and still going with the original glass.


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## fitter9 (Feb 14, 2014)

the wife and i went to atlantic city for the weekend 2weeks ago. the first thing we wanted to do when we came home was fire up the stove. while i was out in the yard getting kindling she was sweeping the hearth around the stove. this is a thread about broken stove glass so guess what happened?? she came outside almost in tears and said she hit the open door with the broom and cracked the glass. i was so mad i had smoke coming out of my ears. still waiting for the glass from the dealer. the ups delivery was delayed because of the latest snow storm. the gas fired steam boiler has been running non stop just to keep the house at 63. my gas and electric bill has only been about 550$ total since i had the stove installed in october. its going to be that much just for the month of  feb. if that glass doesnt get here soon.  i just showed her that video from Kuma stove and i asked her how hard she was sweeping. i thought it was funny.....she did not !


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## tarzan (Feb 14, 2014)

BrotherBart said:


> My old stove has glass in the doors. 21 years of burning in the house and eight years burning in the backyard and still going with the original glass.


Ok BB, gotta ask. How come ya burning a wood stove in your back yard?


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## BrotherBart (Feb 14, 2014)

Don't care for firepits and it makes a great redneck meat smoker.


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## husky345 vermont resolute (Feb 14, 2014)

Hickorynut said:


> I wipe my hot door glass all the time with a paper towel wet with cold water, always thought the glass was thermal resistant.  If it can take the heat then..................


I do the same with a damp cloth every day


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## Hogwildz (Feb 14, 2014)

Good luck with that.


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## firefighterjake (Feb 15, 2014)

fitter9 said:


> the wife and i went to atlantic city for the weekend 2weeks ago. the first thing we wanted to do when we came home was fire up the stove. while i was out in the yard getting kindling she was sweeping the hearth around the stove. this is a thread about broken stove glass so guess what happened?? she came outside almost in tears and said she hit the open door with the broom and cracked the glass. i was so mad i had smoke coming out of my ears. still waiting for the glass from the dealer. the ups delivery was delayed because of the latest snow storm. the gas fired steam boiler has been running non stop just to keep the house at 63. my gas and electric bill has only been about 550$ total since i had the stove installed in october. its going to be that much just for the month of  feb. if that glass doesnt get here soon.  i just showed her that video from Kuma stove and i asked her how hard she was sweeping. i thought it was funny.....she did not !



So inquiring minds want to know ... did you win enough at Atlantic City to pay for the new glass?


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## fitter9 (Feb 15, 2014)

lets see..losses in ac, the broken glass, and the huge gas and electric bill. the wife might have to get a second job.


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## Sunfish (Feb 15, 2014)

We've had three stoves with glass since 1980 & never broke any glass.


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## dvto2 (Feb 17, 2014)

Sunfish said:


> We've had three stoves with glass since 1980 & never broke any glass.



I have relatively small pieces of glass on a double door of my CDW Federal Airtight and one pane was broken with a hockey puck, fortunately, not during the winter.  The stove has some pretty good grates in front of the glass, but I have wondered what I should do if the glass ever breaks while I am burning.


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