How Long Canning Jars Take to Seal (And How to Tell)


Do you wonder how long it takes for canning jars to seal? You’re not alone. It’s a common concern, particularly among those new to canning jars.

It takes a minimum of one hour for canning jars to seal, but it could take longer. To ensure they are correctly sealed, it’s best to leave the jars undisturbed for at least one full day. To test the seal, press the center of the lid, and if it does not move, then the jar is sealed.

Canning is a method of food preservation that involves a bit of science. When done safely, jar canning is an effective way to preserve food with a stable shelf life. 

Can You Seal a Jar Without Boiling it? 

You can seal a jar without boiling it using two safety-approved methods of home canning: the boiling method and pressure canning. Low-acid foods should be processed at temperatures higher than boiling water, hence pressure canning. High-acid foods are sealed with the boiling method with added acid.

Use the Boiling Method for Highly Acidic Foods

This method is sometimes referred to as a hot water bath. Jars are submerged in boiling water to seal. The steps are easy to follow. You must ensure the jars are fully submerged, and at least 2 inches (5.08 cm) of water should be over the jar’s lid. 

The boiling method best suits highly acidic foods, including fruits, jams, jellies, fruit juices, salsas, pickles, relishes, and condiments. All these foods require the correct balance of acid. 

Choose Pressure Canning for Fruits, Animal Products, and Vegetables

Pressure canning doesn’t require as much water as the boiling method. The seal is created by steam pressurizing the jars. Pressure canning requires an additional kitchen gadget, like the Presto Canner and Cooker (available on Amazon.com).

Despite the additional cost of the pressure canner, it has its advantages. Most significantly, it’s the only method that the US Department of Agriculture recommends as safe for canning vegetables, meats, poultry, and seafood. Many find this method to produce more flavorful results.

The disadvantages should be mentioned as well. Pressure canning can be very intimidating. This method relies on a dial-gauge to reach the right temperature, and the dial must be checked annually to ensure that it is still accurate. 

Avoid Unsafe Canning Methods

Again, only the two above methods are safe. Below are ways that are occasionally used but should be avoided:

  • Microwave canning
  • Open-kettle canning
  • Oven canning
  • Steam canning

Using the canning methods could pose a severe food safety and health risk. Please, use the boiling method or pressure canning exclusively. 

Adjust Your Methods When Canning at High Altitudes

If you live at 1000 feet (304.8 feet) or more above sea level, you must adjust your recipes, pressures, and processing times. Water boils at different temperatures at different altitudes due to atmospheric pressures.

If you’re canning with the boiling water method at a higher altitude, you add time; on the other hand, when pressure canning at a higher altitude, you would increase the pressure. 

Do Canning Jars Seal As They Cool?

Mountain Dew Jelly Jars
My “famous” Mountain Dew jelly

Canning jars seal as they cool. A two-piece cap that consists of a flat metal lid with a compound substance and a metal band ring secures the jars. The cooling process begins after removing the jars from the pressure canner or boiling water bath, creating a vacuum effect and sealing the jar.

Should Lids “Pop” After Canning?

Lids should “pop” after canning. However, it’s fine if the lids don’t “pop” after canning because they don’t always do that. The popping sound usually comes about a few minutes after you remove the jars from the canner and place them on a towel.

Watch closely, and you’ll see the lids going up and down. Once the jars are completely cool, check the lids to ensure they’re indeed sealed.

As discussed, the popping sound when opening the jars doesn’t always happen. While hearing this popping may be anticipated or even satisfying, some jars just simply may not pop. Although it may be disheartening, this is okay, as long as they are indeed sealed. 

How Do I Know if My Canning Jars Are Properly Sealed?

You know your canning jars are properly sealed if you push on the middle and their lids don’t spring up. Canning jars are also properly sealed when their lids make high-pitched ringing sounds. You also know your canning jars are sealing properly when their lids don’t bulge.

Below is a quick summary of how to determine if your jars are properly sealed: 

  • Press down the center of the lid. There should be no give. If the lid does not spring up, the jar is sealed correctly. 
  • Use a spoon to tap on the lip of the jar. When you tap the lid of the jar with the bottom of a metal spoon, you should hear a high-pitched ringing sound. A dull sound indicates that the jar may not be adequately sealed. 
  • Check the lid if it’s concave. Is the lid concave? The vacuum created during the sealing process causes the lid to dip inward. Hold the jar at eye level. If the lid is flat or bulges, the jar is not sealed. 

How Long To Let Jars Sit After Canning?

Let jars sit for 12 to 24 hours after canning. Doing so will give the jars time to cool completely. Do not disturb the jars during this time. Moving jars during the cooling period could result in improperly sealed jars.

Can I Reprocess Jars That Didn’t Seal?

You can reprocess jars that didn’t seal. It’s common for jars not to seal properly. You should remove their lids and check for small nicks if this happens. Replace the jars and the lids. Then, reprocess the jars in 24 hours. The processing time should be the same as before.

By doing these steps, you can reprocess your unsealed jars successfully.

Reasons a Jar May Not Seal 

Before discussing the reprocessing steps, here are some common reasons jars fail to seal: 

  • Chipped jar rim: Imperfections on the lid typically result in a failed seal. 
  • Improperly filled jar: You must fill the jar with the appropriate amount. Some space, usually ¼ inch to 1 inch (0.635 cm to 2.54 cm), is needed between the food and the top of the jar. This space is necessary to allow the food to expand once heated—it also plays a significant role in creating the vacuum seal. 
  • Misaligned lid: Canning jar lids have a sealing compound. The compound is designed to contact the jar’s rim. 
  • Unclean jar lip: There may be some spillage as you fill the jars. Wipe the lip to ensure the lid forms a tight seal. 
  • Over-tightened ring: While the ring needs to be secure, a ring that’s too tight prevents air release during the canning process. 
  • Overly quick jar processing: If you don’t process the jars long enough, they won’t seal properly. It’s always important to process your canning jars for the appropriate length of time.
  • Wrong jar type: You must use jars designed specifically for canning. 
  • Incorrect handling of the jar: If you lift the hot jar out of the canner by the lid, doing so can result in a failed seal. You should remove the jar from the canner by the neck, never the lid. 

It would be beneficial if you take the time at this point to determine why your jars may have failed to seal so you can prevent it as you go through reprocessing.

How To Reprocess Jars That Didn’t Seal

Basically, you follow the same steps as you did processing it, with really just two additional tasks. 

To reprocess jars that didn’t seal:

  1. Check for chips.
  2. Transfer the contents into a new jar if there are any nicks along the rim.
  3. Put a fresh lid on the jar.

Lids can’t be reused, whether you’re reprocessing or making a new batch. Lids have a sealing compound that is only good for one use.

Additionally, the jars swell during processing, slightly changing shape permanently. 

However, lids are multipurpose. You can still use them to top jars stored in the freezer, for dried goods, and various other ways, as long as it is not used for canning. 

Refrigerate Unsealed Jars Instead of Reprocessing

If you would rather not go through the ordeal again, you can opt not to reprocess. Processing only gives your canned food a stable shelf life.

An unsealed jar doesn’t ruin the food. You can put the unsealed jars in the refrigerator for immediate use. Or, you can remove the contents and place them in a freezer-safe container, and store them in the freezer.

Sealing Tools

Jelly Making Tool Kit
Just a few canning tools in my arsenal

The first step you should do to seal a canning jar properly is to have the right tools for the task. Here’s a list of everything required for canning:

  • Canning jars: You’ll need jars to can jars, like these found on Amazon. They are very popular, reasonably priced, and often sold in bulk. 
  • Canning lids: They’re often sold with jars, but, unlike jars, they’re not reusable. It’s a good habit to have extra, just in case. Make sure to match the lids with the corresponding jar, like these regular mouth lids.
  • Canning rings: They’re sometimes called bands. While the rings are an essential part of the processing and sealing steps, you should store your canned items without the rings. 
  • Deep saucepan or canning pot: You can use a canning pot or canner for both sealing methods (discussed below).
  • Jar lifter: A jar lifter is a handy tool designed to firmly grip and remove the jars from the canner or saucepan. This lid lifter is what I recommend. 
  • Towel: When the jars are removed from the extreme processing temperatures, you must avoid a drastic temperature change. Your countertop could be too cool, causing the glass to enter thermal shock, breaking instantly. Be sure to place the jars on a towel and no other surface directly.

Final Thoughts

Canning can be intimidating. There are horror stories if you scour the internet. But when you follow the appropriate guidelines, like waiting at least an hour for your jars to cool, you’ll find that you can do it safely at home.

Thanks for stoppin’ by!

Anne James

Hi, I'm Anne but my grandchildren call me Jelly Grandma. I have over 50 years of experience as a Southern cook and am a retired librarian. I love sharing what I have learned. You can find me on YouTube as well! Just click the link at the bottom of your page.

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