How to Vacuum Seal Mason Jars

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The short answer: vacuum sealing mason jars means placing a flat lid on a clean, dry jar of dry food, then removing the air with a jar attachment on a vacuum sealer, a cordless electric jar sealer, or a chamber sealer. When the vacuum releases, outside air pressure holds the lid tight. It keeps dry goods fresher, but it does not can food, so perishables still need the fridge or freezer.

Below are all three methods step by step, what to store (and what not to), troubleshooting for lids that will not seal, and the food safety rules from extension services.

Before you start

• Jars: regular-mouth (2.75 in. opening) or wide-mouth (3.38 in.), per Avid Armor's jar hood specs. Check rims for chips and cracks.
• Lids: two-piece canning lids. The flat lid must be undented with an intact sealing compound.
• A pump: an electric jar sealer, a jar attachment for your vacuum sealer, or a chamber sealer deep enough for jars. Not sure which to buy? Our mason jar vacuum sealer guide compares them.
• Food: dry and at room temperature. Never seal hot food in jars.

Method 1: Jar attachment on a vacuum sealer

This uses the accessory port on a countertop sealer, such as a FoodSaver, Nesco VS-12 or Anova Pro.

1. Fill the jar with dry food, leaving about 1 in. of space below the rim so the food does not get pulled toward the hose.
2. Wipe the rim clean and dry. Dust from flour, coffee or powdered milk is the main cause of failed seals.
3. Set a flat lid on the jar. Leave the ring off.
4. Fit the jar attachment over the lid. FoodSaver's sealers come in regular-mouth and wide-mouth versions; Avid Armor's hood fits both sizes with a flexible silicone gasket.
5. Connect the hose from the attachment to the sealer's accessory or canister port.
6. Run the canister or accessory cycle. Press down lightly on the attachment as the pump starts, so it seals against the jar. Nesco's VS-12 guide gives the same tip for canisters.
7. Stop when the pump shuts off, then remove the hose and lift the attachment off.
8. Check the lid: it should be pulled slightly down and should not lift when you pry gently at the edge. Screw the ring on for protection and storage.

Method 2: Cordless electric jar sealer

Electric jar sealers sit right on top of the lid and need no countertop machine. Nesco's VS-MJ-2N1 is a typical example: cordless, rechargeable, one-button operation and automatic shut-off, for regular and wide-mouth jars.

1. Charge the sealer fully before a big session.
2. Fill the jar and wipe the rim.
3. Place a flat lid on the jar, ring off.
4. Set the sealer on the lid. Use the adapter that matches your jar size, if your model has one.
5. Press the button and hold the sealer steady until it stops.
6. Lift it off and check the seal, then add the ring.

This is the quickest method for a few jars at a time.

Method 3: Chamber vacuum sealer

A chamber sealer evacuates every jar inside it at once. You need a chamber tall enough for jars to stand upright. Avid Armor's JARMAX has an 8.5 in. deep chamber that holds six pint jars or four quart jars per cycle; most home chamber sealers we compared are about 2.25 to 5 in. deep inside. Avid Armor quotes a verified buyer of its shallower USV32 who broke jars laid on their sides, so do not force jars into a chamber that is too shallow.

1. Fill the jars and wipe the rims.
2. Put on the lids and rings, with the rings loose, so air can escape from under the lid. This is Avid Armor's instruction for the JARMAX.
3. Stand the jars upright in the chamber.
4. Set the vacuum time (Avid Armor recommends 25 seconds on the JARMAX) and run the cycle. The seal bar does nothing to a jar; the vacuum does the work.
5. Let air return to the chamber. The rising pressure pushes the lids down.
6. Tighten the rings and check each lid.

See our Avid Armor chamber sealer review for more on the JARMAX.

What to store in vacuum-sealed jars

The pantry list matches what Nesco and Avid Armor recommend for their jar sealers. For long-term dry storage in bags, see our guide to Mylar vacuum seal bags, and for coffee specifically, vacuum sealing coffee beans.

Food safety: vacuum-sealed jars are not canned jars

This is the part many online guides skip.

• No heat, no sterilization. University of Minnesota Extension points out that vacuum sealing a jar involves no heat treatment, so it does not produce a shelf-stable product the way canning does. It also cautions that the seal may not be truly airtight, because the plastisol sealing compound on the lid is never heated.
• Never vacuum seal hot food in jars. The same extension guidance warns against filling jars with steaming food and vacuum sealing them.
• Manufacturers agree. Nesco states that jar vacuum sealing is not equivalent to heat or pressure canning. Avid Armor says its JARMAX does not heat, cook or sterilize food and does not replace a pressure canner or water-bath canner.
• Low-acid, moist food is the danger zone. Clemson Cooperative Extension (HGIC 3865) warns that Clostridium botulinum can grow at room temperature in moist, low-acid foods in a low-oxygen environment. A vacuum-sealed jar of soup, vegetables or meat on a pantry shelf is exactly that environment.
• For shelf-stable vegetables, sauces and meats, can them using a tested recipe from the USDA Complete Guide to Home Canning or the National Center for Home Food Preservation.

"Vacuum-sealed canning jars" in the pantry should therefore hold only dry foods. Everything else goes in the fridge or freezer.

Troubleshooting: when the lid will not seal

• Dirty or chipped rim. Wipe it with a damp cloth, dry it, and inspect it. Retire chipped jars.
• Worn or dented lid. Reused flat lids eventually stop holding vacuum. Try a fresh one. (For actual canning, USDA guidance calls for new flat lids every time.)
• Attachment not seated. Press it down at the start of the cycle and make sure the gasket sits flat on the lid.
• Weak pump or leaky hose. Check the hose connections. If your sealer struggles with bags too, its gaskets may be worn; see how to use a vacuum sealer for care tips.
• Powder in the hose. Fine powders can get pulled up. Put a coffee filter on top of the food before sealing.
• Ring too tight in a chamber sealer. Air cannot escape under a tight ring. Leave it loose during the cycle.
• Lid pops loose later. The jar has lost vacuum. Reseal dry foods; if it held a perishable food in the fridge, use it soon or discard it.

Common mistakes

• Storing perishable food in vacuum-sealed jars at room temperature.
• Sealing warm or hot food.
• Filling to the brim, so food is pulled toward the attachment.
• Laying jars on their side in a shallow chamber.
• Assuming a sealed lid means the food is canned. A pump-sealed lid can look identical to a canned one.
• Skipping labels. Write the contents and date on the lid.

FAQ

Pick the right tool

If you seal a few jars a month, a jar attachment or cordless jar sealer is all you need. If you are putting up a freeze-dryer's worth of food, a jar chamber machine saves hours. Compare every option in our best mason jar vacuum sealers.