Mason jar crack?

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Manfoodcook

Assistant Cook
Joined
Feb 15, 2020
Messages
3
Location
WI
Hello, new to the forum here.

I haven't found anything online about this so I figured I'd give a forum a shot. I recently noticed a strange curved crack on the bottom (near the center) of one of my canning mason jars. It's only on the outside and doesn't seem to go through to the inside. I started to check other jars and noticed many have a near identical looking crack. I was trying to figure out what is driving this, if others have noticed it, and if these jars should be tossed. The jars are all pint Ball or Kerr, and range from older/newer/wide/reg.

Hopefully the attached pics will work. Thanks for your input!
 

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Were you using them for water canning? It's possible they got cracked clinking together when moving the pot.

I do know you can never use them for canning again. Maybe as dry storage for herbs and spices. I would never put anything hot in them again.
 
I can not really tell from your pics. Cracking can occur for a variety of reasons - not using a rack under the jars in the canner, scratching the jar with sharp knives, probably the most common is drastic changing of temp of the glass (filling a cool jar with hot or the reverse) ..... and sometimes they are just defective!!


But since you have more than one I would say it was something in your process the last time you canned. I always fill my jars straight out of the boiling water that I sanitize them in and always put them on a towel (not on the counter) to fill, fill one at a time and place on the rack hanging on the top of my canner that is already hot.


If they are cracks and not mold marks - do not use them again for canning. To be honest I would trash them so that they would not be mixed up with the good ones (imho).
 
Thanks for the replies. The jars get used for water canning pressure/water bath and always used a rack. The widemouths also got got used for freezing. I am just going to toss them after reading a bunch on it. I really just found it weird that I have like 20 jars with this similar crack in them. I guess I will pay attention and try to see if more pop up and from what process. I posted a closer pic of a different jar. It sure looks like a crack, but I can only feel the crack from the outside. Thanks.
 

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Do you still have any new jars, that haven't been used yet, to compare to? If it were me, I would be sure to check all new jars I got to see if they looked like that.
 
I just bought a new case of Kerr pint widemouths, which all jars look good. I can use those as a control for now. I showed a friend and they said they had a few like that too after looking. At least it's not just me :)
 
They don't look like cracks to me, and not located where cracks would be expected to occur. It looks like the natural part of glass making to me. I've canned for decades and would not hesitate to use them for pressure canning or BWB canning.
 
They don't look like cracks to me, and not located where cracks would be expected to occur. It looks like the natural part of glass making to me. I've canned for decades and would not hesitate to use them for pressure canning or BWB canning.

From the photos, that is my impression as well. I wouldn't want to say anything definite from a photo.
 
I've been searching for info on this. I have the exact same thing in the Ball jam jar -8oz jars. BRAND New - never used. I looked at jars in store - and almost all had these same semi-circular lines - that look like cracks - on the bottom. But not ALL have them. Odd. So - those with more experience (Im a newbie) think these are ok to use in water bath canning? (Looking to make some jam!)
 
I noticed the same marks on the bottom of my BALL jars. Mark seems to be on all jars with markings on the bottom. All the jars which have no markings on the bottom doesn’t have this mark. I also checked new jars at the store and they also have this mark. So the mark is on the jars coming from the manufacture. I reached out to BALL directly and they informed me that the circle that looks like a cutout is called a swung baffle and in most cases is safe. As long as it doesn't go outside of the ridged area the jars are safe for canning. They also informed me that the photo I provided is ok to use.
 

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I've never seen crack in mason jars, just glassene envelopes.

images
 
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