Sneak Preview: Vacuum-sealing Mason jars doesn’t always work. Learn about the possible reasons and some tricks to try.
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I experienced a classic case of seeing things differently after experiencing this myself.
Over the last eleven 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.
I would gently repeat the original instructions, and most would write back saying something was upside down, backward, inside-out, or topsy-turvy. 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. So NOW, I feel your pain, with apologies to all who had difficulties.
In this case, I think it is my jar, although that may not be the case for you.
Why my Mason jar wouldn’t 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 not 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 entirely unnoticeable to the casual observer, but I can feel it with my fingers. It looks like this jar will receive a new job description that doesn’t include storing lettuce.
Are you having trouble sealing the flat lids 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 the flat lids if you aren’t heat-sealing, so this will happen occasionally.
2. Does the rim of the jar have a crack or chip?
If you find one, this jar won’t work for vacuum sealing.
3. Is there a piece of food between the lid and the edge of the jar preventing a clean seal?
I hope this is the problem because it’s an easy fix.
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 researcher discovered that ten worked out of twelve brands she tried, and two did not. So 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 use a hand-held sealer, you may not be pressing firmly enough or at the right angle.
The goal is to create a seal between the sealer and the attachment. Try applying more pressure to the white FoodSaver lid attachment.
Readjusting the angle of approach solves the problem for me 95% of the time.
9. If you use a full-size FoodSaver machine with a port, your hose may not be attached securely and completely.
Make sure the hose inserts as far as possible into the machine port. Also, make sure the hose to the attachment is secure.
10. No matter your method, 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, pump it several times and then pump one more time.
A tip that might help
FoodSaver suggests using two flat lids, one on top of the other, if you have difficulty getting a seal. Remove the second lid when you finish since it has served its purpose.
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. Therefore, I only buy wide-mouth jars when purchasing new ones. 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 have another suggestion based on your experience, please 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 questions or suggestions, email me privately for a quick answer: Paula at saladinajar.com. Hope to see you again soon!