Canning Jars....What size, brand, etc.

[aflineman]

Mainly Ball wide mouths and lids. We do a a few Mason jars and a couple of other brands. Some are quite old, but still work for us. This year we have put up both quarts and pints. Pints work well at my work trailer, since I am only cooking for me.

[ronjnk]

I can't add much here. We have about 650 jars of a couple different brands. Jelly, pint and quarts. We do favor wide mouth. Processing time and density does affect the size we choose for a particular item. In any given year, my wife will can 300-400 jars as a guestimate. Over 30 plus years, that's a lot of jars filled.
I want to share an experience we had within the last year. Failures in canning are rare here with a few jars failing to seal in a canning season. She was pressure canning something. The processing was done and she had taken the lid off the pressure canner after it was safe to do so. She was getting ready to take the 7 quarts out of the canner when one jar literally blew it's top with such explosive force that we ended up cleaning the kitchen ceiling of splatter. The jar remained intact, the ring and lid both exploded off of this jar. We have no explanation and after all these years, it is a first.
I don't want to scare anyone off of canning. Just keep your face from being directly over the tops of the jars when removing from the canner. I shudder to think if her face was in the "zone" and the potential medical problems we could have been faced with out here. Ron

[ronjnk]

In thinking about my previous post, I can only think of 2 reasons why a lid would blow off with great force. Either she didn't screw the ring on tight enough or the ring is too old and lost it's strength. We tossed the ring to be safe.

[canid]

there are a couple possibilities:

1.) the jar was actually sealed before heating, or very nearly sealed, such that the expanding fluid was unable to escape as the temp in the jar rose. the pressure inside the cooker had not dropped all the way (or it would have blown before openeing) and the sudden change lowered the pressure to below that required to keep the jar from failing.

2.) the jar was not sealed but the pressure was not even nearly equalized and the pressure change when opening the cooker was so dramatic and sudden that it sucked the loose lid off upon opening.

in both of these scenarios; the pressure inside the jar was still much higher than the abmient pressure (outside the cooker) which means that in either case they had not cooled sufficiently before opening. it is also extremely probable that the pressure inside the cooker was still much higher than the ambient, or it would just as likely have blown at any point after the heat was turned off and the pressure was dropping.

in either case, this is a case of operator error, and you must make sure your cooker has cooled enough to reach equilibrium with and ambient pressure before opening.

in neither case could a loose lid itself have been the problem. you want them screwed down just tight enough to sit flush with the rim of the jar, so that the expanding gas can escape as the jar heats, and get sucked back down against the rim when the pressure begins to fall. the goal being that the volume has been reduced and you achieve a vacuum seal.

[Rick]

I have to agree this wasn't a lid failure per se. Something prevented the jar from reducing pressure. It seems to me the ring may have been too tight before being placed in the canner. The pressure would have built up but would not have been able to reduce. The sudden loss of water cover and the movement of material inside the jar as it was being lifted out was probably enough to cause the failure. Whatever the reason I'm glad she was okay. Not only could she have been injured from the lid or ring but she could have easily been scalded by the hot material inside the jar. Your warning is both timely and noted!!

[canid]

i completely failed to consider the effect of movement on the pressure and i'm glad you brought that up.

[Rick]

Easy to miss, that one. I'm reminded often with my shirt buttons. Pressure and movement, you know. I may go to 80 pound monofiliment.

[ronjnk]

Thanks folks for the input. Some good feedback. The books say to finger tighten the bands so they are snug as has been noted above. Another book says to screw band down firmly without using full force. Our pressure canner will Not allow opening until it is safe to open. There is a safety lock on it that triggers once the pressure drops to zero. Probably a good thing to look for if someone is buying a new pressure canner. Get one with that safety feature so you aren't guessing. Use the lid as protection when taking the lid off so that you don't get a face full of steam. We'll never know exactly what the exact cause was. Fortunately, she has canned many thousands of jars over the years and this was a first and hopefully last.