Canning 101: Why You Should Bubble Your Jars

July 28, 2010(updated on October 3, 2018)

bubbling the relish

Often, when you read a recipe for pickled vegetables, chutneys, relishes or whole fruit preserved in a syrup solution, you’ll come across a phrase that says something along the lines of, “bubble your jars thoroughly.” For new canners, this is often a confusing statement. What exactly is the recipe asking you to do and why do you need to do it?

When a recipe instructs you to bubble your jars, it is telling you to take either a plastic or wooden utensil (I really like that long, skinny spatula you see in the picture above. However, a wooden chopstick or a plastic knife work well too) and insert it into your jar. You use that utensil to wiggle your product around in order to release any trapped air bubbles. You do this after you’ve packed your jars and topped them with your brine or syrup (or after a chunky sauce/chutney/relish has been ladled in).

The reason you want to choose a tool that is made of either plastic or wood is that they will not scratch up the insides of your jars. Metal utensils can leave very small scars behind that end up shortening the lifespan of your jars. When working with glass, it’s always a good idea to do what you can to prevent breakage. This is one of those things.

The reason it’s important to rid your jars of trapped air is that in canning, the empty space to product ratio needs to balanced carefully. You need to have enough air in the jar so that after processing, the escaping heat can pull the oxygen out of the jar and create the vacuum seal. However, too much air and you find that some of your product is left sticking out of the preserving liquid, leaving it prone to discoloration and the development of off-flavors.

Additionally, if you leave those air bubbles trapped somewhere in the middle of the jar, they may try to escape during processing and can end up pushing some of your liquid out of the jar, leaving you with even less of your precious brine or syrup.

If you’ve had that loss of liquid happen to you in a previous canning attempt, don’t despair! As long as the seal is good and firm, the contents of the jar are still fine. You will want to move them up to the front of the consumption queue though, as they will not keep as long.

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74 thoughts on "Canning 101: Why You Should Bubble Your Jars"

  • I canned tomatoes and cucumbers this weekend (I used your garlic dill pickle recipe again!), and I did have some tomato leakage due to improper headspace. I was wondering if it was okay to use (it has a good seal), so thank you for answering my question!

  • I made Salsa last night. I bubbled my jars and did not have any fluid loss. Howver this morning I notice bubbles in some of the jars. I can only guess that this is from the boiling processes? Any suggestions?

  • Thanks for this simple answer. I’ve always wondered about this, especially about the metal vs wood/plastic.

  • I’ve wondered about this, too. Thanks for the information. I just canned my first thing last weekend. =) So proud of myself.

  • Another terrific explanation, Marisa.

    The Chicago Tribune food section had a short piece on refrigerator pickles today in which it described canning as “laborious” and mentioned fears of botulism. Aargh! I fired off an email asking why they had to be so negative.

  • I had some syrup leak out of my peaches this week from too much air in them. It produced some very sticky jars and more work for me to clean them!

  • ah – so that’s the WHY. I stopped doing it even though my mother taught me to because I didn’t know why. You are a great teacher! Thanks.

  • I made a batch of watermelon rind pickles about 2 weeks ago & I didn’t have quite enough brine to fill all of the jars to the top so I just split it evenly between them. I ended up with about a 1/2″ space in each jar where the pickled rinds are out of brine. They processed/sealed fine & I have been giving them a few good upside-down shakes everyday so that the exposed part doesnt “dry out”. Do you think they should be ok? I’ve been waiting to open them for a few weeks to let the flavors combine.

  • I’m all in favor of bubbling. However, I’ve had trouble getting the little plastic spatula around the jar when I’m using regular-mouth jars. Has anyone else had problems with this? I still bubble them, but it doesn’t feel like it’s doing any good because it’s hard to get around the curve of the mouth.

  • Heather, since the seals are good, I imagine that your pickles should be fine.

    Cate, that difficulty in getting around the curve is what led me to using the thin, flexible spatula you see above.

  • When making fig preserves, I inverted the jars to get a good seal. The jam is stuck to the top of the jar, and I have the “headspace” at the bottom. Any ideas?

    1. Laura, it sounds like you got a really good set on that jam and since they were upside down during cooling, that’s how the jam set. There’s really nothing you can do at this point except hope that gravity will eventually move the product downward to the bottom of the jar. For future reference, that’s not actually a recommended technique for ensuring a good seal these days.

  • Thanks for this explanation. I’ve been wondering: I’ve read that, when you’re going to process your jars less than 10 minutes, you need to sterilize the jars in advance. But do you also have to sterilize the chopstick (or whatever) that you use to “bubble”? (Not to mention the funnel and anything else that touches the product.)

    And another question that relates to this post: Is it better to err on the side of too much headspace or not enough headspace? I try to get it just right, but my counter is a bit uneven, so it’s hard to be precise.

    1. Becky, if you’re going to process for less than 10 minutes, you should sterilize your equipment (although, I’m sure if those plastic funnels would really stand up to the boiling required for sterilization). And, it’s typically better to err on the side of a bit more headspace.

    2. I’ve been canning for 24 years. I have always sterilized/boiled my jars and all equipment that the food comes in contact with in an enamel pot including the funnel, jar lifter, spatula, tongs, lids and rings. That is what I read in Ball’s Canning Book in my early 20’s. For me, this is just another step of knowing that I sterilized everything for safety concerns and practices.

  • HMMM.. I have a ?? I just made sweet pickle relish and ended up with nearly 60 ounces of leftover brine. (I had doubled the recipe). I’ve refrigerated it and am curious if I can use it in another batch of sweet relish OR what I should do with it. I hate to waste it. Certainly didn’t expect to have so much liquid left after making the relish.

    LOVE THE SITE. Thanks for all your hard work to share your knowledge and passion with others.

  • Sheila, you can reuse that brine in another batch as long as you use it promptly (2-3 days) and you refresh it with a bit more vinegar (to make up for the liquid that’s lost upon the second round of heating).

  • I have a canning question and you always have great information. I have been making a lot of jam, but there are only 2 of us and I would like to make a variety of pressure canned sauces ready for quick meals. I plan to pressure can a variety of beans and meat and would like to have different sauces, with and without vegetables (curried eggplant comes to mind) to throw together after work. Do you have any advice or cautions for filling my pantry this way? Thank you, in advance for your help.

  • This is EXACTLY the info I needed. I canned creamed corn and green beans this weekend, my first time using a pressure canner. I ended up with a number of jars with the product sticking out of the liquid. Glad to know I’m not the only one with this problem and that I can still eat what I worked so hard to can. Thank you.

    1. Kathy…..I read your post that you canned cream corn. I have been looking for advise on how to do this. If you would be so kind, please tell me how you did it. I have read that cream corn is just the corn scrapped off of the cob. How do you make it into cream corn?

  • Thank you for this! I just did pickles for the first time 2 weeks ago and just today noticed that there are some pickles sticking up above the brine in a few jars. Truth be told, I did not bubble them and now know I should have. I’m glad to know I don’t have to throw them all out – just eat them up quickly :o)

  • Any tips for bubbling jars when you have arranged the jar contents in such a way that you want ingredients to appear decoratively around the sides? You know what I mean, when you have put a vanilla bean down the side of your jam, or a chilli down the side of your pickle. I’ve just put basil leaves against the inside of the jar then filled with tomato sauce. Wiggling the chopstick about to release bubbles spoilt the look of it even though I was really careful. Oh these conundrums!

  • Oh, this is the mistake I made too. My first batch of pickles are sticking out of the brine slightly after boiling. How long will they last in the cupboard? How long in the fridge? I was hoping to keep them until Christmas. I guess I’ll just make more and remember to bubble them this time.

  • Hi, I have just started preserving and made some chutney last night. The recipe did not mention bubbling. I noticed some small bubbles in the jars and I am wondering if this makes the chutney unsafe to eat/affects storage time etc. All jars sealed well.

    1. Tamara, that’s fairly normal, particularly with thicker products. Your chutney should be perfectly safe and the storage time should not change.

  • argh… So i just made canned peaches. Bubbled them but obviously not well enough. Liquid was seeping out for about 3 minutes after i took them out of the boiling water. If there is a good seal but all the fruit isn’t covered. How long do you have to eat them? Whats the approx shelf life when the sugar water isn’t to the top?

  • Brook, insufficient bubbling is one of the things that causes siphoning. However, sudden changes in temperature can exacerbates it. One way to reduce that seepage is to leave the jars in the water bath for 4-5 minutes after the time is off. Kill the heat and remove the lid, to allow the heat to drop a little. After five minutes, pull the jars out. They shouldn’t siphon nearly as much.
    Just keep an eye on the jars you’ve already done. Eventually the fruit will start to discolor and will lose some quality. You should have at least six months before that starts to happen, though.

  • I canned some peaches and bubbled them but am fairly new at it, when I took them out of the hot water bath, I noticed a small amount of bubbling in one or two. They sealed correctly, will this be a problem. Are they safe to store and eat?

  • Thanks for all the info on canning! I just started about three weeks ago – went nuts and planted 12 varieties of tomatoes. Our weather in So Cal was not real great for the crop, but my Japanese Trifele plant went nuts and has given me about 60 pounds so far. It’s a really dark red tomato. First I made sauce – attempted to boil it down, so now it looks like sauce and tastes like sun-dried tomatoes. Guess I used the wrong tomato for that one! Way too juicy. Next batch (about two weeks later) was crushed tomatoes. Canned about 6 pints. That went well, but tomatoes separated from liquid – no big deal as you have said. Now, more tomatoes are coming. Will try your tomato jam next – sounds wonderful and have really become tired of peeling and seeding. I also dried the tomato skins in a slow oven until completely crispy – have ground them in an old coffee grinder I keep for spices and they smell great! Can use the powder for topping just about anything that I want a faint tomato taste and not the bulk or liquid of the actual veggie. Thanks for your blog! – Barbara

  • I bubbled my jars of thickish tomato sauce and ended up with a few bubbles, but everything sealed fine and I’m not worried about that. I washed the jars off after processing and the stuff inside moved around a bit, understandably. However, I’m left with some of the sauce hanging onto the rim of the jar (the inside) where I have left headspace room — and it’s not falling down to the rest of the sauce. Why is it just sticking up there, and is this normal?!

  • Hello,I am completely new to this canning process. I have a question,please.
    I cooked a beef stew and immediately packed it into hot jars and promptly put it into a new All American pressure canner. I did bubble it very well.
    I was nervous as this is my first time and did not know what to expect so,I left more than an inch of headspace because one of the ingredients in my beef stew was pearled barley and I did not know if this would expand further in the canning process.
    So, here is my question,When it was time to remove the lid of the canner and let the jar sit and have a cool down time while still in the canner I heard the lid pop and seal while adjusting to the room temperature. For the next several hours I saw bubbles rising to the surface. The seal is tight there are no bubbles now and the food is not discolored. I did this a few weeks ago and the stew still looks fine. I am just wondering if it is normal to see bubbles rising to the surface even though I heard the seal pop and become concave. Is it possible that even though I heard it pop and become concave that it was still going through the sealing process and so air was still able to escape?

    1. Even if the jar is sealed, the air bubbles that were tucked down in the stew will still rise to the top of the jar during the cooling process. They’ll just gather up at the top of the jar. Sounds like this is what happened to you. Provided you followed instructions for pressure canning beef stew, I’m sure your jars are just fine.

  • Thank you ,Marisa,this sets my mind at ease! The bubbles all disappeared after the jar was completely cooled down. It has been 17 days and the stew still looks good. There is no cloudiness or discoloration.

  • Hi,
    My wife and I just canned our first thing, we did cooked pinto beans in a pressure canner for 75 minutes and they sealed great. I noticed when I took them out and set them to cool there were bubbles bubbling to the top which I figured was normal but it seems the liquid that we used (leftover cooking liquid) has gelled and there are air bubble stuck in it throughout. Is this dangerous the lids are sucked down tight and everything looks good other than the bubbles. We left the correct amount of head space called for in the recipe.

  • Hi- I just canned (raw pack- waterbath) 20 pints of tomatoes= although I pushed the tomatoes down very tight in the jars : added white distilled vineger- and waterbath processed them- and the seals are tight concave- I got some air bubbles in the jars – do I need to worry about this????

  • I just made my first sweet pickles and I have a couple questions. First, I had a really hard time packing the jars with the pickles. The cukes were cut into circles and very crispy; they didn’t want to fill the jar properly and broke when I tried to push them down. That meant more empty space for the pickling liquid to fill, but I didn’t have as much liquid as I thought I needed. I ended up with about 1/2 inch of headspace. I got good seals, but worry that the extra air will spoil the pickles. Next time, can I make extra pickling liquid to add to the jars. Also, would it be easier to pack the jars if I cut the cucumbers into chunks instead of disks?

  • I just made blueberry jam for the first time ever, and tried canning for the first time too. My question is, is it normal for the flat lids to be loose directly after processing, or did I mess up that jar?

    1. Michele, the jars don’t seal until you take them out of the canner. So the flat lids are convex for the first few minutes until the seal is formed and they go concave. So as long as the jars sealed eventually and they are currently hard and concave, your jam is fine.

  • I just made a batch of sweet pickles. The cucumbers were cut into slices and packed in the jars as tightly as possible. After adding the brine and processing the pickles in the canner for 10 minutes, upon removing the jars I noticed that almost all of the jars have about an inch or so of “free space” on the bottom. The cucumber slices all rose to the top. How can I avoid this in the future?

  • I made green tomato relish last but did not put it jars. I just let it cool. Can I reheat it and still can it? How long should it be processed? The recipe didn’t give times, just said it could be canned. T he recipe made more than I thought it would.

  • Hi there,

    I just made pickled okra and bloody mary beans (pickled green beans essentially) and after hot packing, brining, and processing I noticed that both items stick out of the brine in the jars…. I bubbled everything, and the brine was topped off to 1/4” headspace. I don’t know what happened. Are these jars still safe to eat/sell at a craft fair? What should I do next time to prevent this?

    Thank you so much!

      1. Liquid loss is normal and it happens even more often with okra. That’s because okra is hollow and so absorbs some of the brine. Don’t worry about it.

  • I made my first batch or canned tomatoes. I diced them and thought I had packed them well, but did not bubble them. My first batch has about an inch of headspace, I think there was some leakage. Are they ok, or should I possibly reprocess them. I just pulled them out an hour ago and I have not checked the lid yet.

  • Thank you for this reassuring post! I got overzealous packing my canned peaches today–I bubbled the jars, but dpacked too many peach halves into each jar so there wasn’t enough room for expansion– and some of the syrup leaked out of a few jars so I turned to the Internet to see if I needed to reprocess (or just freeze the content of those jars). Good to know I’ll be all right if they sealed properly, which it’s a bit early to tell.

  • Just finished making some green tomato salsa/relish and notice there are some air gaps in my relish. The jars sealed without any leaking during processing, but wondering if the relish will be ok with these air bubbles?

  • After filling jars with tomatoes, I tighten them with hands, then placed in hot water canner. I noticed bubbles coming out from the jar tops. Is this normal or did i not tighten them enough?

    1. That is totally normal and is what you want to see. Those bubbles are produced as the jars vent their oxygen. That venting is necessary to create the vacuum seal once the processing time is done and the jars are removed from the canner.

  • I’m crying. 🙁 I canned 30 quarts of vegetable soup in a water bath as I do every year. 13 of those jars hissed and leaked 3 days afterwards. Their broth was cloudy. I have 17 jars left. Are they good? Should I throw them away? They look fine (not cloudy) and they haven’t exploded yet. The headspace is still good. The ones I threw away look as if their headspace was lost?? I’m not sure what to do with the other cans of soup???

    1. It is not safe to can low acid foods like vegetable soup in a water bath canner. You should only do it in a pressure canner. I wouldn’t eat any of that batch.

  • just canned cucumber relish put in water bath for 10 min but left about1in headspace in each jar will they still be good? thank for your answer

  • I canned chow chow for the first time and I used twice as much cabbage as it called for. From 1 qt to 2 qts, all other ingredients were accurate. My relish hardly had any brine, go figure, but I did manage to get 4 pints, all with proper head space. It’s just that it was rather thick without a lot of liquid. Are they still safe to eat considering chopped vegetables to vinegar ratio will be off? Don’t want to kill the family.

    1. It’s never a good idea to alter the dry weight-to-acid ratio of a recipe. Although you may get away with it, a 100% inaccuracy such as doubling the dry weight for the same amount of brine is, IMHO very risky at best.

  • Your website is wonderful!! I have canned before, but it has been awhile. I’m really enthusiastic about canning again and have canned some pickled okra and sweet pickles. I had some questions about the head space in the jars, but all my questions have been answered here. Your answers have given me the confidence to continue canning. Peaches and chow chow are next on my list followed by some homemade veggie soup!! thanks so much for this wonderful information!!

  • at the end of my water bath process, 2 of my jars were floating above water level when I removed the lid to my pot. ?
    I have never had this happen to me. I was canning apple slices in a very light sugar/cinnamon syrup.
    any ideas?
    I’m still waiting to see if they seal, but I think I will just eat those 2 right away…:)

  • I got this great idea to pack a lot of fruit into each jar, which is easy to do when you hot pack. Now, after losing some liquid when I processed the peaches and pears…..there is very little liquid in the jars. I found one site that said to toss it if you lose 1/2 of your liquid. It appears I have lost that much in many of the jars but everything in the jar is nice and wet, just not much liquid sloshing around. Will my fruit be ok? Do I really have to toss it? Should I just open everything and re-process it or freeze it?

    1. Do you mean that your canner isn’t full? You put the jars you have in, make sure they’re fully submerged in the water and process. You don’t have to run a full canner load every time.

  • Is it alright to use a stainless steel spatula with a silicon tip to exhaust air bubbles out of the jars during canning???

    1. As long as the metal doesn’t come into contact with the interior of the jars, it should be fine. The reason we recommend using plastic or wooden tools to remove the bubbles is simply to prevent scratching the interior of the jars. That kind of scratching can lead to jar breakage.

  • Here is a related question: I have made jam and jelly from fruit that I previously froze several times and only, in this one instance, did my jam come out with millions of little air bubbles. In fact, I followed the same recipe the week before (from the Ball book of canning & preserving) and my jam had little to no bubbles.
    In this one instance, at the beginning of the cooking process, the peaches were not completely room temperature soft when I starting the jam making process. I think that the change in state from frozen slush to boiling liquid created air pockets that I trapped upon adding the sugar. I have given most of the jars to family with suggestions to open, refrigerate, and use quickly (since it’s bourbon peach jam, I am assuming that won’t be hard for most of my family to do), but I am curious if anyone reading this has made a batch like this and tried to keep it on the shelf and/or how the jam kept with time (?).
    Lemon juice was added to balance the pH, all other aspects of Ball recipe followed strictly.
    Processed this batch, as I always do, in a boiling water canner for 10 minutes, cooled on wire rack, washed and heated jars before filling, used seals heated in almost simmering water, etc.

  • I just jarred picked red onions and removed the air bubbles. After the water bath the onions floated to the top and there is a large amount of liquid in the bottom of jar. Is this shelf stable still?

    1. If you raw packed the onions, that’s pretty normal. As long as the jars are sealed, they are safe.

  • I made pickled garlic and a couple jars had foamy bubbles at the top after a few days of sitting …. Is that normal ? I’ve already done 30 jars before these and the only change to the recipe I made was apple cider vinigar instead of white

    1. Hmm. That’s not normal. Is there activity in the jars? Do they look like they are developing active bubbles? It sounds like it could be fermenting.