How long do your lids take to POP?

highalttransplant(z 5 Western CO)September 18, 2008

So today I made my second batch of Annie's Salsa, even better the second time by the way, but I had a bit of a scare afterwards.

Up to now, all of my jar lids have popped within 5 - 10 minutes of removing from the BWB. Only two did that this time, but I know the 24 hour rule of not touching the jars so I was nervously waiting (while cooking dinner and bathing kids), and after an hour, the remaining jars finally popped down, and I breathed a big sigh of relief.

What determines how long they take to pop? How long do yours usually take, and how long before you start to panic?


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Mine usually pop within a minute of taking them out. I've found that for some reason, the more vigorous the water bath is boiling the faster they pop.

    Bookmark   September 18, 2008 at 11:20AM
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busylizzy(z5 PA)

Some pop minutes after removing, others take time.
I don't worry about it until the next day when I am removing the bands for storage, then I recheck.
I had a spaghetti sauce jar lid pop off easy when I was putting away the first batch, guess what I had for dinner?
I do, however note when removing from the canner how convex the lids are. The nice dome will complete it's seal when cooled,if all clean and rubber ring working.

    Bookmark   September 18, 2008 at 11:48AM
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ksrogers(EasternMass Z6)

Head space has something to do with it to. If very small headspace at the top, the vacuum created takes longer to pop. If air bubbles are presnet that can also slow it down. Maybe you might want to consider using more head space, like a bit more than 1/2-1 inch. The filled jars should have its product just barely come up to the glass bead below the threads. Sometimes, I don't hear the pop early on, but pressing down slight makes it pop. If I shake the still hot jar, the lid will pop back up again, and then will pop down once its cooled off. That condition to me, is evident that the vaccum inside is just barely able to pull in the dimpld on the lid. Now, I fill with a bit more head space and that issue has not been repeated. Be sure to check the jars a few days later, as some can lose that weak seal and strt to allow air in. Never boil new lids, but leave them in slightly simmering water until ready to apply them one at a time.

    Bookmark   September 18, 2008 at 12:08PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

I've found that thicker products may take longer to seal than the ones that are more liquid. Some things can take several hours. If they still haven't sealed after the jar has cooled to touch, I reprocess them.

I also go buy the % of seals. In other words if I did 7 quarts of the same thing all at one time and 6 sealed quickly but 1 didn't, I figure the odds are that 1 jar isn't going to - likely has something under the lid - and so needs re-processing.

Re-processing = back to the beginning, not just sticking it back into the BWB or PC for another run. ;)


    Bookmark   September 18, 2008 at 1:40PM
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greenhouser(Middle TN Zone 6)

Mine always pop withing minutes. Those that don't aren't likely to seal. Those go in the fridge for immediate eating rather than reprocess them.

    Bookmark   September 19, 2008 at 2:13PM
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highalttransplant(z 5 Western CO)

Well, when I wiped the jars down, after the 24 hr waiting period, all of the jars had sealed just fine, with nice concave lids.

There was between 1/2" and 3/4" of head space on all of the jars, so I don't think it was a lack of headspace. I thought maybe since most of what I've canned has been in 1/2 pint jars, that maybe the bigger containers took longer. This batch was a little thicker than the last one, since I made sure to drain the chopped tomatoes really well this time, so it could have been that I guess.

I live at an altitude of close to 5,500 ft. Would that make any difference (other than the extra processing time in the BWB)?


    Bookmark   September 19, 2008 at 2:51PM
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melva02(z7 VA)

Bonnie, the lids pop when the pressure outside is greater than the pressure inside, by a difference great enough to overcome the stiffness of the lid. Let's assume the stiffness of the lid is constant among all lids, although in reality it depends a little bit on temperature.

The air inside the jar heats up during processing. Some of it leaves, which is good. Not all of it leaves, or else there would be no matter in between sauce and lid, and then the pressure of the water would pop the lid inside the pot. This could never happen by the laws of physics, because the air is escaping slowly enough that if the pressure around the jars in the pot were greater than the pressure inside the jars, the lids would be held closed and no more air could get out.

So, we have jars full of hot air at high pressure. Since the volume available to the air is roughly constant (space between sauce and lid), the pressure varies directly with temperature (i.e. they go up or down together). When the jars come out of the canner, the air starts to cool down. If the jars were nothing but air, the air would cool pretty quickly, and the jars would seal fast. But the heat from the product inside the jar keeps letting its heat into the air inside the jar (as well as through the jar into the surrounding air). So that keeps the pressure up longer and delays the pop.

The time to pop should be based on the pressure inside the jars at the time they come out of the canner, the ambient air pressure, the temperature of the air inside the jars, the ambient air temperature, and the heat capacity of the product in the jar. Jam and other sugary products have a higher heat capacity than water (think of how much more it hurts to get burned by caramel than by water). The temp/pressure inside the jars at t = 0 of cooling time should match the temp/pressure of the pot they came out of, which is why some (most?) pressure-canned things seal before they come out of the water.

So differences in sealing time of different batches are probably based on different thickness of the product and different ambient conditions at your house. Humidity is also a factor because it affects the ability of the ambient air to cool the jars.

Now the part I need to think about. Differences between you at 5500 feet and me at 150 feet are probably based on the lower pressure at your location. It's pressing less hard on the jars, so it needs lower pressure inside the jars before it can push the lids down. (Remember, science never sucks. It can push, pull, etc., but it never sucks.) The question is, what is the pressure inside the jars when they come out of the BWB? For a given volume (headspace), your jars are starting with fewer molecules of air because you have lower ambient pressure. So maybe fewer of them feel the need to escape during processing, and you and I have the same molecules of air inside our jars at the end, though yours would be at lower temp because of the different boiling points of water. This might require some real math. Let's leave it aside for now.

To answer one of your questions directly, science would predict that bigger containers take longer, because there is a greater heat source inside the jar keeping the air hot and pressurized for longer. A thicker product might have greater heat capacity. Hard to say because water has very high heat capacity but syrup is even higher. The other factor is, if they're cooling slowly, you might not get a violent flexing that makes the loud pop. The lid can gradually reverse its curvature, so they are sealing even though they didn't ping you.

Sorry to go on, just thinking out loud. Discussion on the science welcome but not necessary.


    Bookmark   September 19, 2008 at 4:23PM
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highalttransplant(z 5 Western CO)

Oh, Melissa, your response made my head swim, LOL! I had to finish making dinner, then come back and read through it a second time. I've always loved the natural sciences - biology, anatomy, etc., but I have to admit to having to use a tutor to pass college physics.

I do believe the lids reversed their curvature gradually, as the sound was more of a ping, ping ping, than one loud pop, like the half pints of jams and jellies did for me.


    Bookmark   September 19, 2008 at 10:32PM
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readinglady(z8 OR)

Science never sucks . . .

I like that, LOL.

I was just noting last night that the lids popped with all the explosiveness of a gunshot compared to the usual piffle. I was using a box of very old lids from DMIL, probably vintage 1960. DH says it's due to higher-tensile steel in the old lids.

Everything sealed beautifully, by the way, in case you find yourselves in possession of 50-year-old lids. Just be sure you bring them to a boil as opposed to the current simmer.


    Bookmark   September 19, 2008 at 11:36PM
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ruthieg__tx(z8 TX)

Don't cha just love that ping sound when they are popping. I always tell my husband to listen for the pinging...I made salsa yesterday and love love love to see the jars sitting on my counter. If I wasn't such a neat freak, I'd leave all my jars out in the open so I could look at them.

    Bookmark   September 20, 2008 at 9:52AM
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