Testing Jar Seals And Reprocessing Jars (Safe Home Canning)

by Merissa on July 22, 2013

in Canning and Preserving

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I think that this is the part that most people panic about when it comes to canning. Did my jars seal? Are they safe for my family to eat? How can I be sure?

The scary thing is that the worst problem that can come from canning (botulism) is unable to been seen or smelled. So what can we do about it?


First of all, and this is the biggest thing...make sure you following the canning directions to the T. Make sure that you boil or cook your canned foods for the correct amount of time and the correct amount of pressure (if you are pressure canning). Make sure that during the time of cooking that your canner stays up to the correct pressure (or keeps boiling if you are water bathing) for the entire time you are processing.

You also want to make sure that you talk to your local extension office and find out if you need to make time/temp/pressure adjustments for your altitude. If you aren't familiar with your local extension office you can locate one here: US Extension Offices. (By the way, if you didn't already know, your extension office is a plethora of information on all things local, outdoors, growing food, ect. Utilize them!)

Once you have the cooking part down you shouldn't have much to worry about. But do you know how to properly test a seal on a jar? Here are some things to look for...

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The most common method for testing jars is the Finger Test Method. Simply press on the middle of the jar lid with your finger. If the lid "pops" up and down with your finger when you press, it's not sealed and needs to be reprocessed. If it doesn't move at all it's sealed.

Note: Don't test canned foods until they are completely cooled and you've given them several hours to seal! Doing so might create a false seal and unsafe food.

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The next method you can try is the Spoon Test Method. Tap the lid with the bottom of a spoon. If it makes a dull sound the lid is not sealed. If it makes a pinging noise it is correctly sealed. Please note that if you did not leave headspace and food is touching the lid it will create a dull sound either way.

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Of course you can also look at the lid at eye level. If the lid looks flat or bulging it's not sealed. If the lid is nice and concave it's properly sealed!

My jar didn't seal...now what?

If your jar didn't seal don't stress and get upset. It happens to the best of us! Even experienced canners that have been canning for decades have jars that don't seal on occasion. If you have an unsealed jar or two, here's what to do.

Remove the lid and rim. Check the rim of the jar for any nicks or cracks. If you have a nick, discard the jar (or use it for dry food storage!) and place your prepared foods in a new, clean jar. Place a new lid on the jar and secure it with a clean rim. (Do not reuse the lid you already processed the jar with.) Reprocess the jar using the same process that you already used. It's a good idea to leave some time in between your canning so if unsealed jars do happen you can just add them to another batch instead of having just a single jar to re-can.

If you don't want to re-process your un-sealed jar you can always stick the food in the fridge or eat it for supper. Or you can just freeze the contents for future use.

How long have you been canning? Do you make sure to follow safe home canning methods?

merissabio

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{ 57 comments… read them below or add one }

1 RevAllyson July 22, 2013 at 2:06 pm

We’re really careful to follow safe canning procedures when we do anything. :) New lids, clean rings, sterile jars, processing times checked, etc. I’ve never had a problem with bad food, although I’ve had plenty of seals fail for a variety of reasons. The exploding jar of spaghetti sauce was the worst, but at least it was contained in the pressure canner LOL…

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2 Colleen July 23, 2013 at 6:28 am

I have a large family to feed, so we can on a large basis. About 300-600 jars per year. Safe canning methods are a huge part of our season. Not only checking lids, rings, and jars, but also making sure the canner seals are good.

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3 happy momma July 23, 2013 at 8:32 am

I have been canning for a while. I have only had a few problems. We did have some salsa that became unsealed after about 6 months. It was the strangest thing. I am not sure what happened but I had about 15 jars that all of a sudden decided that they did not want to be sealed anymore. It was very sad to throw them all out. But then I had jars ready to be filled up with something else.

When I open up a jar I always ensure that the seal is still intact and I usually listen closely when I open it up. If I am in doubt, I will throw it out. I am not afraid to “waste” food if I am not sure of its quality even when It makes me sad. I try hard to ensure that it is good food for the family.

I know some people have had real trouble with the reusable canning lids. It is hard to tell if they are sealed, you don’t get that concave look, nor the sounds. They seem to have about a 50% failure rate. Many times you will unseal them trying to see if they are sealed. They seem to be a pain to use. I would not recommend them. Just stick with the old tried and true canning lids is what I think.

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4 Merissa July 23, 2013 at 8:33 am

I agree, regular canning lids seem much easier to use and now that they are taking the BPA out of them I’m more than happy to keep using them!

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5 Sue in Oregon July 26, 2013 at 4:05 pm

Merrisa, I am a 70 year old wife, mother and grandmother. I find your blog so refreshing and encouraging and just want to say “ThankYou” for the courage and knowledge you are sharing with others. I have been canning for years and get some strange looks when talking about ‘putting food up’ and canning. My mother-in-law gave me my lessons when I moved to Oregon and I have thanked her each time I pop the seal on a jar for teaching me a craft that has provided food for my family during some pretty lean times.
I have learned to take advantage of fantastic meat sales to can and have on hand for several years. Abundance in fruit and vegetables gardens of friends brings out the water bath canners/pressure canners and on food is on the shelf for future use.
I encourage men and women to learn how to can. Go to a senior center and talk with canners. Check out Extension Services at your local college for canning classes and teaching brochures. Your advice to follow directions “EXACTLY” in the Ball Canning Bible is right on. YouTube is also a great visual lesson for new ideas. Again, just like me tell you that I think what you share with others is a great service and very interesting. As my grand daughter would say……You Go Girl!”

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6 Merissa July 26, 2013 at 4:06 pm

Thanks for all the advice and encouragement Sue!

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7 Kim September 21, 2013 at 2:11 pm

I pressure canned peaches. I had some difficulty with the canning process (all the ater boiled away)> the jars all sealed. as long as the jars are sealed is the food safe to eat?

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8 Merissa September 21, 2013 at 2:12 pm

Did you boil the water for the correct amount of time? If not, even though they look sealed they may not be safe and you might want to stick them in the fridge and use them.

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9 Carolyn in Michigan September 28, 2013 at 2:34 pm

I used to can a LOT. But haven’t now for quite a long time. I recently was given a bunch of extra produce and decided to “put up” some of it. If I have to reprocess any of it, do I need to empty, clean and refill the jars…or just switch out the lids and put them in the water bath? Thanks!

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10 Merissa September 28, 2013 at 2:56 pm

I don’t empty the jars, I just remove the lid and rim, then clean off the rim of the jar, replace it with a new lid and then reprocess.

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11 Beth February 25, 2014 at 4:38 am

Great topic. As a relatively new canner (2 seasons) safety is a major concern. We always follow the directions very carefully and attend carefully when opening the jars. I have two questions for all of you experienced canners out there that will ease my mind greatly.

1) We check for head space when canning, but often it changes after processing. Is this OK? If we had 1/2 inch head space to start and the food moves around or shrinks, is the food still safe?
2) When we open, I like to hear a loud “pop” to know that the seal was intact. But sometimes we perform the above tests with success, open the jar, hear the suction/seal sound, but not the “pop.” Is this food safe, or do we need that loud pop?

We tossed 3/4 of our tomatoes because I didn’t hear the pop, but they seemed OK and I felt sure I was doing the wrong thing by throwing them out.

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12 Merissa February 25, 2014 at 7:13 am

I hope this helps…

1. Yes, food changes when it’s canned (especially foods like potatoes or beans that absorb the liquid) so some shrinking is ok.

2. I also listen for this, not necessarily for the pop but just that the jar lid was hard to open and doesn’t come easily off. This isn’t the best indicator though, as long as the jar passes the test in the article above before it’s opened it should be fine.

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13 Elaine March 31, 2014 at 8:31 pm

Just a word on the tomatoes, my Grandma & Dad both have always tod me, “No one has ever died from eating bad canned tomatoes.” If you have a bad jar of tomatoes, you will know the second you open it. The smell will tell. I am in my 30’s and still don’t can alone-I have grownups =] that I team up with. I have learned a lot and can’t wait for this years garden to provide a colorful pantry.

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14 Merissa April 1, 2014 at 6:15 am

I want to caution that this isn’t necessarily true. Botulism cannot be smelled from a jar so it’s hard to detect.

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15 Mathieu February 26, 2014 at 11:47 pm

Hi Merissa,
The best test you can do to verify your lids are correctly sealed is by lifting the jars by the lid (you need to remove the ring to perform the test). If there is any issue with the seal, it won’t be able to lift the weight of the jar and it will unseal.
Obviously you need to wait for the jars to cool down to execute this. This apply to reusable lids as well :)
Mathieu.

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16 Linda Jett July 19, 2014 at 11:48 pm

I canned green beans and peas and squash and tomatoes. They all sealed except 1 jar. I cooked in a water bath – the quarts 45 minutes and the pints 30 minutes. A friend now tells me that these items cannot be done in a water bath and should have been done in a PC for that length of time – not a water bath. That she would not eat them…….What do you suggest??? Thanks so much…….

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17 Merissa July 20, 2014 at 9:25 am

Yes, all of those foods should be processed in a pressure canner to be safely sealed. If you just did them you should be able to re-process them in a pressure canner.

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18 Marsha July 30, 2014 at 8:51 am

We did ours In a pressure canner but mistakenly covered the jars with water but did them 25 minutes on 10lb pressure as chart indicated. One person told me I needed to reprocess them is this correct? will it ruin the green beans by reprocessing? I thought as long as the beans are boiled when cooking them later for at least 10 minutes or longer any toxins would be destroyed. Help!!

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19 Merissa August 7, 2014 at 9:10 am

I’m really not sure on this one. I’ve never covered jars with water when pressure canning. I would call your local extension office and ask them wheat to do.

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20 Patch September 26, 2014 at 2:02 am

BOILING for at least 10 minutes will break down botulinum toxins — be sure it’s actually boiling for those 10 minutes, not simmering, not just heating, but boiling.

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21 Jay August 1, 2014 at 12:50 pm

Hi,
As I lifted a jar of tomatoes out of the water to place on the counter to cool and “POP:. (seal). A very weak sounding, Pop was heard. The lid sunk in too. I am use to setting them down then hearing loud pops as they seal. Do you think that weak sounding pop was good enough?
Thanks’
Jay

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22 Merissa August 1, 2014 at 4:06 pm

It might be ok but if you are worried that something hitting it might have caused the pop I would just stick it in the fridge and enjoy now.

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23 Sharon K August 2, 2014 at 3:06 pm

I’m just teaching myself how to can. Yesterday for my second attempt, I made a batch of nectarine chutney, and then some oven roasted nectarine butter. A few questions re the latter. 1) I got the recipe for the nectarine butter off the net, from someone’s cooking blog, and had been listed on a larger canning blog. But, it occurs to me, how do you know if a recipe is an “approved and tested” recipe, and based on safe canning rules? 2) The recipe just called for roasting the fruit until soft, mashing, optionally adding sugar and spices to taste, then canning for 15 mins in a hot water bath. Should it also have had lemon juice to make it keep? 3) I realize now that I didn’t leave enough headroom. The butter rose to the bottoms of the lids, and there are small traces of fruit on the outside of rims of the jars. But, the lids don’t move, are concave, and tight. Are they really sealed?

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24 Merissa August 3, 2014 at 6:35 pm

You can generally learn the latest about canning from your local extension office. I make various fruit butters all of the time and haven’t added any lemon juice to them, usually the fruit is acidic enough for the water bath. It sounds like the jars are probably sealed but since little room was left they may not stay sealed for long. In this case it would probably be best to enjoy them sooner rather than later.

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25 mike August 8, 2014 at 11:50 am

I put up several quarts of meat spaghetti sauce I left 1″ of head space ,, processed at 11 psi for 70 minutes ,, each jar had boil over and I noted content down the side of the jar ,, I’m guessing that I need more head space?? Sauce was “hot packed”
Can I reprocess again right away ? I just heard 3 pops ,, I guess I’ll wait 24 hrs and see where they are ,, we’ll eat lots of pasta this week !!!

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26 Merissa August 8, 2014 at 12:53 pm

I would take off the lids, take some out and reprocess right away. Without leaving enough headspace you run the risk of the jar not sealing right and you definitely don’t want the jars to go to waste or get bacteria in them. You should be fine to reprocess if you just did them.

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27 mike August 9, 2014 at 7:30 am

Melissa ,Thank you so kindly for the fast reply!
Only 1 jar did not seal ,, I put that in the fridge,,, the others have good concave lids and have the sound as described above when tapped,,, as this is my first time pressure canning it’s more or less a test to see if I could do it,,, my question now is I exactly measured 1″ headspace,, and had 11 psi ,, why the boil over? For sauce that is precooked/hot packed is it necessary to process for 70 minutes?? I saw on another website (after the fact) that hot packed food only needs to be processed for 15 minutes at proper pressure because your not “cooking” product only “sterilizing” it and 15 minutes will do that

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28 Megan August 10, 2014 at 9:03 pm

I am new to canning (first year) and a week ago I removed a jar of peppers out of my canner and I hit the top of the lid without thinking. Do you believe that this created a false seal or do you believe it is okay? I hate to throw away four jars of peppers but don’t want to make my family sick. Before I read your post I did not know that you could have a false seal. I just assumed that it would seal or it wouldn’t. Also, has to much time passed to reprocess the jars?

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29 Merissa August 10, 2014 at 9:59 pm

Personally I wouldn’t eat them but if you feel they are safe then it’s really a judgement call. I wait no longer than 24 hours before re-processing anything.

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30 Todd August 11, 2014 at 7:43 am

I was canning hot sauce and did a boil bath for 30 minutes. I let the jars completely cool down for several hours then I did the finger test. As I did the finger test some jars were not sealed but the lid did not pop back up creating a seal. All the jars seem sealed now as I did the finger test again the morning after. Could they be sealed properly now?

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31 Merissa August 11, 2014 at 8:08 am

I personally wouldn’t trust a jar that could possibly have a false seal. If it’s been less than 24 hours you can re-seal.

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32 Kristen August 13, 2014 at 8:36 pm

I made cherry jam with our tart cherries, first time canning ever and a few of the lids I messed with by pressing them instead of waiting on them to pop on their own. I don’t know which jars those are now, how do I know if they are properly sealed now? Does pushing on them too early cause them not to seal properly?

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33 Michelle Smith August 15, 2014 at 12:08 pm

I made salsa a week ago while in water bath the water flowed over and put out the flame soon as we discovered it we lit the burner returned to boil and started our time again. Is it safe? Also same salsa had to much head space I was leaving town so I tossed it in the refrigerator can I reprocess it now a week later?

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34 Pamela Urbanczyk August 23, 2014 at 12:20 pm

How many times can I ‘re process…my jars are leaking when I take them out of water bath.. bad seals??

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35 Merissa August 23, 2014 at 3:44 pm

I wouldn’t re-process more than once. To make sure the jars don’t leak next time you will need to make sure they aren’t packed too full and have ample headspace, plus the lids will need to be very tight. After a second re-process if they don’t look right I would just stick them in the fridge and use.

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36 Betty August 23, 2014 at 3:12 pm

Why do I not hear the same ping when I water bath as I do when I pressure can?
My water bathed jars sealed but I never hear them.
Is this normal?

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37 Merissa August 23, 2014 at 3:45 pm

You may not hear them if they seal inside the pressure canner. Most of the time mine are sealed by the time I get them out.

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38 Betty August 23, 2014 at 4:58 pm

These were peaches and I water bathed them. They looked sealed.But never heard a ping. They have not sit long enough for me to test the jars.

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39 Sophie September 5, 2014 at 7:23 pm

I made a small amount of tomato jam and just intended to keep it in the refrigerator and eat it later that week. I filled some clean canning jars (because the recipe said glass jars or plastic containers could be used) with the jam, let it cool a bit, put the lid on, and put it in the refrigerator. At some point in the refrigerator, I suppose the lid sealed because it had an indention that popped up when I opened it. Is this safe to eat?

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40 Merissa September 5, 2014 at 7:57 pm

How long has it been in the refrigerator? As long as it’s been in there since you placed it in the jar and it smells fin then it should be fine.

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41 Sophie September 5, 2014 at 8:54 pm

It has only been in there for three days. Before I put the lid on the jar, it set for a little while to cool (I didn’t want the jar to break or anything) I had opened the jar earlier today and it smelled fine, but I was a little worried because my knowledge of food preservation is limited and I didn’t want to make myself sick. Thank you for responding

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42 Merissa September 5, 2014 at 8:55 pm

Oh you should be just fine. :) Enjoy your homemade goodies!

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43 Jenna September 9, 2014 at 9:18 am

I was checking the seals on my jelly after they sat overnight. A few of the lids popped down when I checked them which I understand creates a false seal. But when I lift the jars by the lid they are holding strong, so now I am confused. Will a false seal hold strong like a good seal? I was getting ready to reprocess but don’t want to take the time if I don’t need to.

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44 Merissa September 9, 2014 at 9:52 am

Yes, even a false seal can create a hold. It’s better just to be sure that they are sealed properly. I would either re-process or place in the fridge and enjoy.

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45 cindy September 16, 2014 at 9:27 am

I canned salsa did not leave in water long enough, cans all sealed should I redo in hot bath even though they are sealed

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46 Joanne September 22, 2014 at 8:23 am

I heard a pop noise when I was in my kitchen, so I checked the jars of salsa that I had canned a week ago and there was a jar that unsealed. I put it in the refrigerator right away, but I am still concerned as to whether it is edible or should I just throw it out?

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47 Merissa September 22, 2014 at 11:36 am

I would toss it, sounds like it somehow made a false seal.

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48 Rachel September 25, 2014 at 6:34 pm

I’ve only been canning for a few seasons and don’t feel very experienced, so I’d love some advice! I just canned apple pie filling this afternoon and thought I’d left enough headroom, but now I’m noticing that in several jars the apples are touching the lid inside. The jars seem to have sealed but sound dull when I tap on them. Do you think they’re ok or do I need to scoop out some apples and reprocess? Thanks!! :)

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49 Merissa September 25, 2014 at 7:57 pm

As long as they are sealed you should be alright, I might just eat them first before others though.

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50 Susan September 29, 2014 at 8:44 pm

Pressure canned 13 jars of salmon today for the first time. 100 minutes. Pressure 12lbs. It did seem like 12 jars had already sealed before I took them out of the canner, they all had a concaved lid. 1 still had the raised lid. I thought as they cooled I would hear a popping. They have been out almost 4 hours now and nothing. Can I assume they did seal in the canner? Or should I wait till completely cool and try pressing or the spoon test?

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51 Merissa September 29, 2014 at 9:09 pm

Wait until they have all completely cooled before testing.

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52 Kim Elkie October 5, 2014 at 12:52 pm

Possible crisis! I am new to canning, doing it alone for the first time this gardening season. Last weekend I was pressure canning spaghetti sauce. It was late in the evening so I was jotting down on a paper what time the next phase needed to start. I just realized I only pressured my quarts of sauce for 10 minutes! I called my mom this morning and she suggested emptying the jars into freezer bags and freezing it all ASAP. It has been exactly a week … is it still good?! The jars were all sealed. It smelled okay I think but I am so upset I am sure I’m looking for a problem/foul smell. So much work into these jars of sauce … I’m devastated at this potential problem. Do you think they are okay? I have already vacuum sealed them into bags and into the freezer. Thank you for your input.

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53 EmilyH October 9, 2014 at 1:49 pm

Hello! I am fairly new to canning as well (1 season; mother and grandmother are seasoned ‘vets’ at it, though!), and had a question regarding my Apple Butter. I used half-pints, and processed 25 jars in total. The first time, only 10 did a successful ‘pop’ while 5 gave a false seal. The remaining did not even attempt to seal. I changed all of the lids to the 15 in question, cleaned the jars and all again, re-processed them within the 24 hour limit, and only 3 out of the 15 sealed. The rest did not. They didn’t even attempt to seal.. I can’t seem to find any imperfections, and left enough head space. My husband and I finally put the remaining jars in the fridge overnight, and now they are all sealed. Should I still freeze them? Or would they be considered correctly sealed? I think I may know the answer… But not positive! Thank you!

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54 Jaya November 6, 2014 at 4:50 pm

How do you know if you have a false seal? I jarred my first batch of spaghetti sauce recently and I went to take one out today, and I was told that you can check your seals by picking the jars up a couple of inches by the lid only (without the ring) and if they open then you know your seal is broken. I did that the day after, however, I just went to open one and did the check again after taking the ring off and it opened right away. I didn’t hear a sound at all when opening it. I think that one’s off…

I then opened another jar, and as soon as I turned the ring I heard a loud popping sound, that one barely smells like anything, as opposed to the first jar that smells strongly of spaghetti sauce (not off- just strong). Anyways! Now I’m rather paranoid…. I put the second jar in the fridge and think it’s fine – I am just wondering if it’s normal for a seal to break when you only take the ring off… Any help would be appreciated! Thanks<3

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55 Lorrie Jean November 9, 2014 at 9:50 am

The spoon theory must be backwards. I just canned 14 quarts of stew. 10 of them make the dull sound, 4 ‘ping’. by pushing on the lids, I could see that the 4 that ping were not sealed. I tested my jars by actually opeing one that was dull and one that pinged. the one that pinged was not sealed.

Wouldn’t it make sense that if the jar is ‘properly’ sealed that the sound would be ‘dull’, there would be no air left in the jar to allow for the noise to reveberate back as a ping.

Confused……

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56 Kayla November 13, 2014 at 9:17 am

So, here is my problem… I canned jalapenos two weeks ago for the first time. I am new to canning, and being that my husband goes through so many jars of jalapenos I thought I should start canning them too. They all sealed, and after a few days I placed them into a small jelly cabinet with my other canned foods. I opened the cabinet today to put some newly processed jars in and when I opened the cabinet I could smell peppers. I picked up one of the jars and took of the ring and smelled the rim of it. Although it is a perfect seal, it seems that the “heat” of the peppers is escaping and it’s quite noticable. Has anyone else had an issue like this? Are these okay to keep, or should they be tossed?

Any advice would be greatly appreciated!!!
Kayla

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57 Maureen Lynn Widmer November 26, 2014 at 7:08 pm

I came across this post from Pinterest. I always read comments, because so often there is additional information that wasn’t originally included.
I am a self-taught canner — both water-bath and pressure-canning. Something that I think is highly overlooked in processing instructions is how important it is to make sure that the rim of the jars are clean, clean, clean! This, I believe, is the biggest contributor to failed (or false) seals. (Of course, NEVER re-use lids. Ever. EVER.)
As a rule, I use a paper towel moistened with white vinegar (instead of water) to wipe the rims before applying the seals and rings. It is a rare thing that I don’t have sealed jars — vinegar cuts through oil, grease, fats and removes residue like nobody’s business!
I also want to stress – especially with pressure canning (meats, low-acid vegetables, etc.) — that it can take quite a long time for those jars to ‘ping’ as they are so hot when removed from the canner. The vacuum is created as the jar adjusts from the hot contents to the cooler surrounding air. Any that are not sealed within 12 hours probably need to go into the fridge for immediate use, or reprocessed. Canning is ‘easy’, if you have a mentor. It can be really scary if you’re continually unsure of the safety of the food you put up. But don’t let that deter you. Find resources, seek advice, and learn this old time method that allows you to feed your family for a season, or for years. Really enjoyed your post, thank you!

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