Gallon glass exploded - no idea why!

[Snowy Pass Maple]

My wife and I just finished over 2 hours of cleaning up the result of the attached photo - hoping the photo may provide some clues.

I was sitting in another room and suddenly heard glass break followed by what sounded like a water leak. Never occurred to me until I got over there that this is what I would find.

This bottle was packed 3-4 weeks ago. No problems when filled hot. I pre-heated it in the oven at 190 F. The bottling was done indoors and it was sitting on my dining room table - has been there at least a week or so. Room was 70-75 F.

Any ideas what could have caused this? Any time I've heard of bottles doing this, it is when they are being filled or subjected to thermal shock - not weeks later while sitting in a climate controlled room. I've only packed maybe 8 of these ever - usually do smaller glass.

You can imagine the mess this created... the bottle managed to crack open in a way that ensured every last drop ended up all over the floor, running through the folding self-storing leaves inside the dining table, all over tons of other supplies I had out in the dining room... had to take the table outside and pressure wash it to get it clean.

9652

[Foremaple]

the only thing I can think of is that, for some odd reason, fermentation was occurring . It can create tremendous pressure.

[happy thoughts]

Sorry about the mess! Any small nick, chip or hairline crack can put stress on the glass and cause it to break in time. The jug may have had a small defect to begin with. Think of a small chip in a windshieild that runs like a pair of nylons when it goes. That said, the one thing I question is heating such a large basically closed jug in the oven. I know people do that for canning jars but that's not recommended by jar manufacturers because of the uneven dry heat which can cause them to crack. Thinking this may have caused some damage to the jug especially if it was wet or had moisture inside it when heated. You might want to consider warming in the dishwasher as it might be less stressful on a glass jug.

[Run Forest Run!]

Snowy Pass Maple, I'm so sorry to see a gallon of your hard work ruined.

As happy thoughts has mentioned, I never trust heating empty bottles in the oven any more either. Even the slightest flaw etc can cause it to explode during the heating process or on the counter after filling, and not always immediately after. Dry heating used to be done all of the time years ago, but is no longer seen as the safest way to do things. I use hot water baths for my jars now.

It's interesting that your bottle is cracked along a seam. I wonder if there was a manufacturing flaw at the seam that might have contributed to your horrible experience. It's hard to say if the crack ran "to" or "from" that seam, but check along the breakage lines for clues that might help you to identify a similar flaw in any other of your gallon bottles.

I've canned and preserved for years and years, and I'm always worried about bottling in large containers. They are really convenient to fill, but if they spoil or break I've lost a whole batch instead of a smaller sampling. After a few bad experiences I rarely use large containers anymore.

I hope that you have lots more syrup from this year to drown your sorrows in. That was such a shame.

[Snowy Pass Maple]

So I had never realized that it was a bad idea to put glass in an oven - and have seen many other mapletraders suggesting to do so as it goes a long way towards eliminating any risk of cooling leading to mold. But sure enough, looking around google, it seems like some jar manufacturers do indeed discourage this - yet a lot of people don't realize that you should not do this.

I would love to hear from anyone that fills gallon glass if they do any preheating at all. I would be a little worried about doing no preheating and introducing a thermal shock when filling, and a water bath is not very practical with these containers.

I do have convection available on my oven which could reduce hot spots - and wasn't using it before. I am thinking that running something like 135 (I think lowest setting on oven) with convection might be safer?

The other possible problems I could think of is that the jug was rinsed before going into the oven. The evaporating water could have been keeping some areas cooler and adding to stress. This was also not the first use of this jug - so perhaps that didn't help.

Fortunately, this was only a small percentage of our crop, and I will confess to scraping a lot of it off the table and chairs to refilter and process into my personal use stash. Maple syrup making seems to present ample opportunities to screw things up to result in commercial "scrap" that I end up consuming :-)

The most bothersome thing about this incident was having it happen 3-4 weeks after fill so hopefully it was an unfortunate freak incident...

[Run Forest Run!]

Snowy Pass Maple, do you have any large pot that would be able to hold the gallon glass jug? I agree with you that putting hot syrup into an unwarmed bottle is not ideal. You don't need to heat the jugs in a water bath after filling (as with traditional canning of preserves) but it would go a long way to prep the jug before filling. The jug wouldn't even need to be covered with water, just heating in it.

[happy thoughts]

The convection oven would be more even heat but it's still dry heat. I think you'd be better off heating them in a dishwasher which is an approved method of jar heating. Use the sanicycle.

[happy thoughts]

The jug wouldn't even need to be covered with water, just heating in it.

I have a feeling partially submerging glass could lead to the same potential breaking problem. Per USDA guidelines jars to be heated in water should to be covered with water but only need to be heated to 180*F..

[Run Forest Run!]

I'll definitely look into that happy thoughts. Thanks for the comment.

[Snowy Pass Maple]

What I haven't been able to figure out is why dry heat is bad for glass... I'm an engineer so I can't help but want to understand that.

I'm guessing that the idea with the dishwasher is that the moisture in the air helps improve the convective heat transfer to the surface so it ends up heating the bottles more uniformly vs. radiant transfer that would be a lot less uniform?

Then I'd think they'd just say put a pan of boiling water in an oven - but perhaps the heating elements still create some radiant heating stress? (my wife does this when baking certain breads since I haven't built her a steam injection system...)

Another easy approach for me would be to just fill the jugs with hot tap water to temper them somewhat and empty the water out just before filling - that would cut the temperature difference to < 80 degrees during the fill.

Hoping some other users working with large glass jugs have some tips on what works for them!

[Cabin]

How old was the jug?? I have had canning jars do that. What was the oven temp? Are you sure about the oven. If the glass is way hotter than the liquid you can crack the glass and it usualy does not show as a problem until you try to move the jar. Not sure why but I have had a few jars leave the buttoms on the table when I picked them up.

[Snowy Pass Maple]

How old was the jug?? I have had canning jars do that. What was the oven temp? Are you sure about the oven. If the glass is way hotter than the liquid you can crack the glass and it usualy does not show as a problem until you try to move the jar. Not sure why but I have had a few jars leave the buttoms on the table when I picked them up.

This was the second use for the jug... had filled once before. Oven was 190 F. It's a normal kitchen oven. Agree with the concern about shock during filling - which was why I went through the trouble to preheat the glass to around the same filling temperature which I see a lot of people on mapletrader suggesting. Obviously we have to rethink that!

One other thing that I will not be doing going forward is putting the filled hot jar on the stone counter - that is also a big temperature difference. But again, I'd expect those issues to fail right after cooling. Not 3-4 weeks later after the bottle has been moved around at least 3-4 times, and has been sitting in a room untouched for days - and then suddenly just ruptures.

[Cabin]

This was the second use for the jug... had filled once before. Oven was 190 F. It's a normal kitchen oven. Agree with the concern about shock during filling - which was why I went through the trouble to preheat the glass to around the same filling temperature which I see a lot of people on mapletrader suggesting. Obviously we have to rethink that!

One other thing that I will not be doing going forward is putting the filled hot jar on the stone counter - that is also a big temperature difference. But again, I'd expect those issues to fail right after cooling. Not 3-4 weeks later after the bottle has been moved around at least 3-4 times, and has been sitting in a room untouched for days - and then suddenly just ruptures.

While I have had a number of jars crack like that after a water bath or boiling the only time I had breakage like that from dry heat the themostat for the oven went bad and was going up to 500+ degrees but saying 200. I always place my jars on a plate with a hot pad under it. And avoid drafts when filling and cooling the glass. Cracks can start out small and will not break open for some time. Probably has to do with glass being a solid 'liquid'.

[happy thoughts]

What I haven't been able to figure out is why dry heat is bad for glass... I'm an engineer so I can't help but want to understand that.

I'm guessing that the idea with the dishwasher is that the moisture in the air helps improve the convective heat transfer to the surface so it ends up heating the bottles more uniformly vs. radiant transfer that would be a lot less uniform?

Then I'd think they'd just say put a pan of boiling water in an oven - but perhaps the heating elements still create some radiant heating stress? (my wife does this when baking certain breads since I haven't built her a steam injection system...)

Another easy approach for me would be to just fill the jugs with hot tap water to temper them somewhat and empty the water out just before filling - that would cut the temperature difference to < 80 degrees during the fill.

Hoping some other users working with large glass jugs have some tips on what works for them!

This is what Bernardin has to say about jar breakage http://www.bernardin.ca/pages/faq/33.php#34


What causes mason jar breakage?

BERNARDIN® mason jars are designed to withstand the repeated heating, cooling and multiple uses associated with home canning. However, they must be handled correctly to avoid certain situations that may result in breakage. The three main causes of accidental jar breakage and preventative measures are outlined below.

1) SCRATCHES: Scratches especially those on the interior surface of mason jars, can weaken the glass and cause breakage when the jars are heated or handled. Scratches are caused by:

Metal utensils used to remove food from jars
Knifing out air bubbles using a metallic utensil
Cleaning jars with steel wool or a wire stem brush

To ensure long lasting durability of your mason jars, clean them with a soft cloth and warm soapy water or in a dishwasher. Only use non-metallic utensils when removing bubbles and serving. Use jar lifters that have a coated surface over the metal.

2) THERMAL SHOCK: Although mason jars can withstand repeated heating and cooling, they are sensitive to quick temperature changes. Sudden cooling or heating can cause thermal shock and result in breakage. These are examples of actions that can thermal shock by:

Pouring boiling water or food product into a room temperature jar
Placing a room temperature jar into boiling water
Setting hot jars on a cool or wet surface
Oven sterilization (Jars heat unevenly due to dry heat and temperature fluctuations inside the oven may be too drastic for the jars)

Always put hot food into a hot jar and never place a jar directly into boiling water. Sterilize jars by covering with room temperature water and bringing to a boil. Boil 10 minutes. Place hot jars on a dishtowel or wooden cutting board when filling and cooling.



So you're on the right track with your uneven heating theory. Not sure if filling with hot tap water would work or not. It might not heat the jar up enough to prevent thermal shock when filling with syrup at packing temp. An 80*F difference still sounds like a lot to me considering that glass doesn't take rapid changes well. You might want to see if you can find the temp range tolerance for bottle glass. But that said, I'm with Karen. Just use smaller bottles :)

[Snowy Pass Maple]

So you're on the right track with your uneven heating theory. Not sure if filling with hot tap water would work or not. It might not heat the jar up enough to prevent thermal shock when filling with syrup at packing temp. An 80*F difference still sounds like a lot to me considering that glass doesn't take rapid changes well. You might want to see if you can find the temp range tolerance for bottle glass. But that said, I'm with Karen. Just use smaller bottles :)

I've heard < 100 F as a rule of thumb in the past. Which also explains the concern of directly filling glass in unheated sugarhouses where the difference can be 150 F. Another point to consider is that when you run your dishwasher, you're regularly hitting your glassware that may be 60-70F with 120-130F water, so all your glass sees a 50-70F difference pretty regularly.

We are only using gallon glass for a restaurant customer - and I would have used 1/2 gallons just to ensure they are opening fresh ones more frequently, but Burch Bottle was out of stock on 1/2 gallon growlers when I picked up.

Anything else we sell is in much smaller glass, and we haven't had a single break in hundreds of bottles last year - but we only oven heated the glass on about 1/4 of those fills. Our market much prefers glass and I like to use something renewable when possible. The good shelf life is another big plus for us when this is still a part time side operation. But it won't take many incidents like that to convert me to plastic for bulk :-)

[happy thoughts]

I've heard < 100 F as a rule of thumb in the past. Which also explains the concern of directly filling glass in unheated sugarhouses where the difference can be 150 F. Another point to consider is that when you run your dishwasher, you're regularly hitting your glassware that may be 60-70F with 120-130F water, so all your glass sees a 50-70F difference pretty regularly

You're right about <100F. I just found it in a discussion on Pyrex breakage and glass thermal stress. In the article they state 55C or ~99*F for soda lime glass, the glass used for most bottles. And good point on dishwasher temps. Now I don't have to worry about which to put in my glass first- the ice or the gin and tonic :)

Here's the link to the pyrex article in pdf. As an engineer you may find it interesting. I too prefer glass myself for many of your own reasons.
http://www3.nd.edu/~rroeder/ame60646/slides/glasscookware.pdf

Good luck getting your orders filled and hope all broken glass is behind you.

[Cabin]

I've heard < 100 F as a rule of thumb in the past. Which also explains the concern of directly filling glass in unheated sugarhouses where the difference can be 150 F. Another point to consider is that when you run your dishwasher, you're regularly hitting your glassware that may be 60-70F with 120-130F water, so all your glass sees a 50-70F difference pretty regularly.

We are only using gallon glass for a restaurant customer - and I would have used 1/2 gallons just to ensure they are opening fresh ones more frequently, but Burch Bottle was out of stock on 1/2 gallon growlers when I picked up.

Anything else we sell is in much smaller glass, and we haven't had a single break in hundreds of bottles last year - but we only oven heated the glass on about 1/4 of those fills. Our market much prefers glass and I like to use something renewable when possible. The good shelf life is another big plus for us when this is still a part time side operation. But it won't take many incidents like that to convert me to plastic for bulk :-)

When you oven heat the jugs do you always start with a cold oven? I like to go from a cold oven to 250 degrees(same temps as a preasure canner) for 15 minutes then reduce the heat to 180 degrees at least 15 minutes before I bottle. I can handle 18 - 20 8 ox bottles at a time. But then this is for personal use and time is not that much of an issue.

[KevinS]

Stress fractures in glass are no where near always instant. and I suspect it had to do with setting the hot glass on the cool stone. use a rack without much mass so it heats up fast. I even set them where I have had plastic ones that were just filled so the temp differential was less.

[Snowy Pass Maple]

To answer a question above - no, I did not start with a cold oven. So this probably didn't help either.

Based on all the feedback, it seems like the following two changes should improve things and I will implement on my next bottling:

Preheat jug to ~120 F by filling with hot tap water or using dishwasher rinse cycle and ensure that the hot filled bottles never go on the stone counter.

Interestingly, my smaller bottles have always been placed on wood, so this could also explain why I never had issues with them. One other question on these large growlers I had was how much headspace do people typically leave when capping hot?

Thanks for all the feedback!

[happy thoughts]

Interestingly, my smaller bottles have always been placed on wood, so this could also explain why I never had issues with them. One other question on these large growlers I had was how much headspace do people typically leave when capping hot?!

I always pack glass on a large wood cutting board. I wish someone that has packed in gallon glass jugs would jump in since I personally have never used them for bottling but as for head space, I think the same would apply for any size jar. Since you don't need to allow room for expansion as in a boiling water bath. I fill them full to about 1/4 in. ( at ~185F). In a narrow necked bottle, that's going to leave about an 1- 1 1/2" head space on cooling (probably more in a gallon sized jug) and keeps the syrup level in the neck where I want it to be. Less head space means less air to support mold growth in storage. I have only rarely gotten jars that fail to seal.

[clarkridgefarm]

Less head space means less air to support mold growth in storage. I have only rarely gotten jars that fail to seal.
Do you reboil the sap and jar if this happens?

[happy thoughts]

Yes, but I don't reboil, just reheat to packing temps (185ish) and rebottle into a clean warm jar with a new lid. Reheating above 200F will create new sugar sand and the syrup would need to be refiltered.

[happy thoughts]

clarkridgefarm- I should have added that I only reprocess those jars that fail to seal within a day of packing. Any container older than that found with a failed seal is likely an indication of spoilage and should be discarded. Thankfully, that hasn't happened to me yet.

[rayi]

I never pack anything over a quart in glass. To fragile. If a customer wants to know what it looks like I can pull the small bottle that I keep from every batch. I have even dropped a gallon and it was OK