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Vacuum-Sealing Mason Jars: 10 Tips for Getting a Good Seal

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Preview: Vacuum-sealing Mason jars doesn’t always work. Find out some possible reasons and learn some tricks to try.

It was a classic case of seeing things differently after you experience something yourself.

Over the last 3 years of blogging about salad in a jar (a method of preserving chopped lettuce in a vacuum-sealed glass jar), I’ve had the occasional reader ask me why they couldn’t get their jars to seal.

10 TIPS FOR GETTING LIDS TO SEAL ON A MASON JAR

I would gently repeat the original instructions and most would write back saying something was upside down, backward, inside-out, topsy-turvy, or whatever. And they finally got it to work.

Then it happened to me. I have one Mason quart jar in my cabinet that will not seal no matter what I do. NOW, I feel your pain, with apologies to all of you who have ever had difficulties.

wide-mouth attachment for vacuum-packing Mason jars

In this case, I think it is my jar although that may not be the case for you.

Why wouldn’t my Mason jar seal?

Regarding the wide-mouth attachment seen above, the blue rubber must form a seal around the ridge at the bottom of the top of the jar (see picture below). If there are any bumps or other irregularities, it may be unable to form that seal.

If you look carefully at the jar in the picture, you can see that the lowest ridge has some ripples. This is completely unnoticeable to the casual observer but I can feel it with my fingers. Looks like this jar will receive a new job description that doesn’t include storing lettuce.

Are you having trouble getting the flat lids to seal on a Mason jar?

Ten tips for getting lids to seal on a Mason jar when vacuum-sealing

#1

Is the flat lid bent?

(You can reuse these lids many, many times so this will occasionally happen.)

#2

Does the rim of the jar have a crack or chip?

#3

Is there a piece of food between the lid and the edge of the jar preventing a clean seal?

#4

Is the rubber gasket on the attachment dirty?

Wash in soapy water.

#5

What brand of jars are you using?

Do they match up to the wide-mouth attachment? The FoodSaver website recommends Ball and Kerr brand jars. However, these are not the only ones that work. One person did some research and found that out of 12 brands she tried, 10 worked and 2 did not. Trial and error may be the order of the day on this one.

#6

Is your jar a mutant like the one I described above?

Use it for something else that doesn’t need to be vacuum-packed.

#7

Foreign particles may be blocking the hole in the attachment.

Check the top of the attachment where the air is sucked out of the jar. If you are packing something powdery, try cutting a piece of paper the diameter of the jar and laying it on top of the contents to prevent the small particles (e.g. powdered sugar or flour) from entering the attachment.

#8

If you are using a hand-held sealer, you may not be pressing firmly enough.

Are you pressing at the right angle, or directly over the center to create a seal between your sealer and the top of the attachment. Sometimes, just applying more pressure to the white FoodSaver lid attachment while you are sealing will cause the jar to seal.

This tip actually solves the problem for me 95% of the time.

#9

If you are using a full-size FoodSaver machine with a port, your hose may not be attached securely and completely.

Make sure it is inserted as far as it will go into the machine. Also, make sure the hose to the attachment is inserted securely.

#10

No matter what method you are using, are you operating the machine long enough to pull out all the air?  

You should hear a difference in the sound of the motor as it slows slightly. If you are vacuum-packing with a hand pump, be sure you have pumped it several times and then do it one more time.

A tip that might help

FoodSaver suggests you try using two flat lids, one on top of the other if you are having difficulty getting a seal. Of course, you will remove the second lid when you are done as it is just laying on top.

I have found this tip most helpful when sealing regular-mouth jars (as opposed to wide-mouth jars).

For some reason, the smaller opening seems harder to seal, which is why I only buy wide-mouth jars if I’m purchasing new jars. Besides that, wide-mouth jars are easier to get the food in and out of and easier to clean.

If you are still having trouble or you have another suggestion based on your own experience, please leave a comment.

p.s. Just a reminder that the vacuum-sealing process is not a substitute for heat canning. Perishable foods must be kept in the refrigerator even when vacuum-packed.

If you have any questions or suggestions, you can email me privately: paula at saladinajar.com.

Hope to see you again soon!
Paula

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