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For a canner, the telltale “pop” of a canning jar sealing is music to our ears. But there’s another “pop” sound that is every canner’s nightmare. The “pop” of a glass jar bottom cracking and popping off shortly after you put a jar full of goodness into the boiling water bath to process. It is a devastating “pop” with all your hard work quickly swirling around the water of the canning pot and making a big ol’ mess.
A number of years ago, I was thrilled to become the new owner of a over 100 old canning jars for free. I cleaned them up and got to work canning with them, all the while daydreaming of the prior homesteading ladies who may have canned in them since the early 1900’s. But I quickly learned that some of these old beauties just weren’t meant to be canned with anymore. In that one season, I lost countless jars of produce and hard work to that awful “pop” when the bottom blew out of the glass jar. I also had multiple jars not seal due to tiny chips in the rim of the jar mouth. A good portion of those old glass canning jars became glass storage jars in the pantry or turned into mason jar solar lanterns to light up our porch at night (we sell the mason jar solar lanterns in our Etsy shop so check ’em out!)
After that season, I swore off using old canning jars. I wish I had the money to buy all new jars to use, but just look at how expensive these babies are! Instead I shop yard sales and gladly take gifts of old, dusty boxes of canning jars from friends to build my stash. Because of this, I make a point of inspecting each canning jar before using it to ensure no more incidents of jar bottoms popping off or lids not sealing due to chipped glass. I’ve had a pretty good success rate the last few years with my canning endeavors and only had one glass jar bottom pop off last season out of the 100+ jars I canned.
Then this year rolled around. Last month we washed and stored a couple dozen canning jars gifted to us by friends. I inspected each jar before placing it in the cardboard box for storage. The ones with chipped jar mouths were put into my stash of jars for food storage in the pantry. The ones with visible cracks in the side or bottom were thrown out to prevent any future breaking incidents from the weakend glass. The boxes of jars were labeled with the size jars and stored in our mudroom.
This week I was scrambling to get some of our ripe apricots canned one afternoon. As I was gathering my canning supplies, I realized the boxes of pint size jars were stored on a high shelf that I couldn’t reach. My husband was at work and there was no ladder that would fit in there for me to use. So I started scrounging around my cupboards for some glass jars. In my rush to get jars, I totally spaced the need to inspect the jars thoroughly. I did a quick check of the jar mouths and got to work.
I was canning a small batch of halved apricots in a light syrup in seven pint jars. As I placed the filled jars into the boiling water canner I heard that awful “pop” of a glass jar bottom blowing out. I removed the jar and quickly tried to ladle the fruit out of the canning water. Then I placed the last of the filled jars and quickly filled another jar to replace the broken one. While I was doing this, I heard another awful “pop”. I was incredulous! Yet another jar bottom blown out and wasted. Two of my batch of seven blown out from the start. All that hard work wasted. Ugh!! It was so darn frustrating. What made the situation worse is that I knew better than to can in jars that I hadn’t inspected first.
After that experience, I decided to share this canning failure here so you all don’t make those same mistakes! Really, there’s nothing worse than having a glass jar bottom blow out in the water bath canner. All the produce is lost and not salvageable. At least if the lid doesn’t seal on a jar after canning it, you can still eat it right away so all your efforts are not lost.
So here’s the deal. When I inspect canning jars, I look for three main things. I’m going to go through each one of these so you know what I’m talking about and can learn how to do a quick canning jar inspection on your own jars. Hopefully then you won’t have to experience the awful “pop” of a jar bottom blowing out in your water bath canner!
Preventing Canning Failures: Canning jar chip inspection
Canning jars won’t seal if there is a chip in the glass rim of the jar. Even the tiniest chip can cause a lid to not seal. I don’t even take a chance anymore. If I see even a tiny chip, that jar won’t be used for canning. Run your finger around the rim of the jar mouth and feel for any uneven parts where a small chip might be that your eye didn’t catch.
Preventing Canning Failures: Canning jar rim inspection
A common issue I’ve come across when trying to reuse old canning jars is leftover wax on the rim of the jar. I’ve been gifted 50-100 year old glass jars with their lids still on, some of them even containing really old food (that we of course threw out and did NOT eat!) When the old lids were taken off, they often left a bit of wax on the jar rim which would prevent a new canning lid from sealing properly. Sometimes you can see this quite obviously, but other times you don’t realize there is a bit of wax on the rim until you run your finger around the jar mouth. Usually we can remove this by using a knife and carefully scraping the wax off the mouth of the jar so the jar can be reused.
Preventing Canning Failures: Canning jar body crack inspection
Look over the body of the canning jar to look for any cracks and fractures in the glass. If you can with a glass jar that has a fracture in it, even a small one, the pressure of the contents inside when canning will blow out your canning jar from that weak point in the glass. Look closely on the bottom of the glass jar for a circular crack. These are the cracks I find trickiest to spot but without fail will blow out the bottom of your jar.
Once you know your jars are crack, chip and wax free make sure they are clean, clean clean! That should be a given though for any canning and preserving you are doing. These tips on doing a glass canning jar inspection will help reduce the amount of canning failures you have. BUT they’re not the only things that can cause a canning failure.
Those pints of halved apricots I mentioned canning earlier? Well, after losing two jars to the bottom blowout I crossed my fingers everything else would go well. Just my luck though, one jar didn’t seal. The jar rim didn’t appear to have a crack and the rim was wiped clean when I put the lid on before canning. Yet when I took the lid off to take a closer look after it didn’t seal, there was a tiny speck of apricot that wiggled its way in there during the canning process and caused it not to seal. Today when I canned 18 jars of apricot jam, not a single jar bottom blew out and every single jar sealed. See, it pays to inspect your canning jars before you can to prevent those canning failures!
Do you have any canning tips to share?