The Basic Method: Using a Vacuum Sealer and a Jar Attachment

You can vacuum seal a mason jar using a countertop vacuum sealer and a jar sealing attachment—a small plastic accessory that fits over the jar's mouth and connects to your sealer's vacuum channel. The attachment removes air from the jar while the sealer's heating strip seals the lid. This method works with quart and pint mason jars and takes about 30 seconds per jar.

Most vacuum sealers sold for food storage come with a jar attachment in the box, though some brands sell it separately. Check your sealer's manual to confirm yours includes one. The attachment typically has a small tube that slides onto your sealer's vacuum port and a flat base that sits on top of the jar's lid.

Key Takeaways

  • A jar attachment for your vacuum sealer removes air from the jar and seals the lid in one motion, taking about 30 seconds per jar.
  • You need a two-piece mason jar lid (the flat lid and the screw band), and the flat lid must be new or in good condition to seal properly.
  • Dry foods like grains, flour, and crackers seal best; wet or oily foods can clog the sealer and prevent a proper seal.
  • Store vacuum-sealed mason jars in a cool, dark place, and check the seal after 24 hours by pressing the lid center—it should not flex.

Preparing Your Jars and Lids

Wash your mason jars and lids with hot soapy water and dry them completely. Any moisture on the jar rim or lid will prevent a tight seal. If you are sealing food that was recently cooked or thawed, let it cool to room temperature first—heat can warp the lid and cause steam to escape during sealing.

Use a new or nearly-new flat lid for each seal. The rubber gasket on the underside of the lid must be intact and flexible. If you have reused a lid before, it may not seal again. The screw band (the metal ring) can be reused, but it only needs to be finger-tight—do not over-tighten it, or the sealer cannot pull air from the jar.

Step-by-Step Sealing Process

Fill your jar with the food you want to store, leaving about one inch of headspace at the top. Place the flat lid on the jar's mouth, then screw the band on loosely—just enough to hold the lid in place. The band should turn freely by hand.

Attach the jar sealing accessory to your vacuum sealer's vacuum port. Set the jar on a flat surface and position the attachment's base flat on top of the lid. Press the sealer's vacuum button or switch. The machine will pull air from the jar for about 5 to 10 seconds, then the heating strip will seal the lid. You will hear a slight hiss as air leaves the jar. When the cycle stops, remove the jar and let it cool for one minute before tightening the screw band fully.

Foods That Seal Well and Foods to Avoid

Dry foods seal best: grains, flour, sugar, pasta, crackers, nuts, dried fruit, and powdered milk. These foods do not release moisture or oil that can interfere with the seal. Herbs, spices, and tea also work well.

Avoid sealing wet or oily foods directly. Liquids and oils can be pulled into the sealer's vacuum channel and damage the machine. If you want to seal soup, sauce, or marinated food, freeze it solid first, or pour it into a freezer bag and seal that instead, then place the bag inside the jar. Soft breads and pastries will crush under vacuum pressure, so skip those too.

Checking the Seal and Storing Your Jars

After the jar cools, press the center of the lid with your finger. A properly sealed lid will not flex or pop—it should feel solid and slightly concave (curved inward). If the lid flexes or pops back, the seal failed. This usually means the lid was not new, the jar rim had moisture, or the band was too tight. Discard the lid and try again with a fresh one.

Store sealed jars in a cool, dark place away from direct sunlight and heat. A pantry or cupboard works well. Check the seal again after 24 hours—sometimes a seal takes time to fully set. Vacuum-sealed mason jars can keep dry foods fresh for several months longer than unsealed jars, though the exact time depends on the food and storage temperature.

Troubleshooting Common Sealing Problems

If the sealer will not pull air from the jar, the attachment may not be seated properly on the vacuum port. Remove it and reattach it firmly until you hear a click. If air still will not pull, the port may be clogged with food particles. Unplug the sealer and use a small brush or pipe cleaner to clear the port.

If the lid seals but pops open after a few hours, the jar rim likely had moisture or food residue. Wash the jar again, dry it thoroughly, and use a fresh lid. If the sealer's heating strip does not seal the lid, the strip may need cleaning. Unplug the sealer, let it cool, and wipe the heating strip gently with a damp cloth, then dry it.

Frequently Asked Questions

Can I use a regular vacuum sealer bag attachment instead of a jar attachment?

No. A bag attachment is designed for the flexible opening of a vacuum bag, not the rigid rim of a jar. A jar attachment has a flat base that sits flush on the lid and creates an airtight seal with the jar's mouth. Using the wrong attachment will not pull air from the jar.

Do I need to boil the lids before sealing?

No. Boiling lids is only necessary for water-bath canning, where the heat process sterilizes the food. Vacuum sealing does not sterilize—it only removes oxygen to slow spoilage. Wash lids in hot soapy water and dry them.

How long do vacuum-sealed mason jars stay fresh?

Dry foods in vacuum-sealed jars typically stay fresh for 6 to 12 months, depending on the food and storage temperature. Cooler, darker storage extends shelf life. Once you open the jar, the food is exposed to air again and should be used within the normal timeframe for that food.

Can I vacuum seal a jar that already has a canning lid on it?

Yes, but only if the canning lid has never been used before. If it has been canned or sealed once, the gasket is compromised and will not seal again. Always use a fresh, unused flat lid for vacuum sealing.

What if my vacuum sealer did not come with a jar attachment?

Check your sealer's manual or the manufacturer's website to order the correct attachment for your model. Most brands sell them separately for $10 to $20. Alternatively, some people use a straw to manually remove air before sealing, though this is slower and less reliable than using an attachment.