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.

Broken Bottle_Small.jpg

[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!