What Are The WECK Jars, And How To Use Them For Canning

Assembling WECK Glass Jars: 6 Simple Steps with Photos

To assemble the one of these jars, simply place the rubber ring (gasket) onto the sealing rim of the lid, position it on top of the jar, and attach the canning clamps. Before you do that, make sure the clamps line up across from each other on the lid. Then, press them down until they click onto the jar’s rim. And that’s it! You’re good to go.

Cleaning and sterilizing WECK glass jars before canning

Just as any canning jars, WECK jars must be thoroughly washed and sterilized before you begin canning. 

The good news, cleaning and sterilizing Weck jars is the same as cleaning and sterilizing Mason jars.

Sterilizing WECK lids, however, can be a bit tricky…

If you read the official WECK insert, the guidance on glass lids and rubber gaskets can feel a bit unclear. Through our own trial and error, we’ve found a practical workaround that slightly deviates from the manufacturer’s instructions, but works far better in a real home kitchen.

Here is our recommended method for prepping the WECK lids and rubber gaskets:

• Separate the lid components: Always remove the rubber gasket from the glass lids before washing.
• Wash the glass lids: Treat them like jars. Always wash in hot, soapy water or run them through a dishwasher cycle
• Clean the rubber gaskets: Wash by hand in hot, soapy water. Do not put them in the dishwasher, as the heat and detergents can cause premature wear.

⚠️ The official WECK instructions recommend attaching the rubber seal to the glass lid and submerging the entire assembly in boiling water for 10 minutes to sterilize it. However, in practice, we ran into two issues with this method:

• Gasket Damage: Boiling the natural rubber for a full 10 minutes degrades the material, causing it to wear out and stretch significantly faster.
• Slipping Seals: Vigorous boiling often causes the rubber gasket to slip off the glass lid before you can safely remove it from the pot.

💡 Our Recommended Workaround:
To save your gaskets (and your sanity), try this method instead:

• Assemble first: Stretch the clean rubber gasket onto the glass lid while it’s dry.
• Use off-boil heat: Bring a pot of water to a boil, then turn off the heat. Carefully lower the assembled lids and gaskets into the hot (but no longer boiling) water.
• Keep them warm until needed: Leave them in the hot water until you’re ready to place them on your filled jars.
• Mind the timing: Don’t let the gaskets sit in the hot water for more than 10 minutes total. This helps them stay flexible without losing their shape.

The Science Behind How WECK Jars Work

When the jar is heated during processing, the pressure inside increases relative to the pressure outside. As a result, hot air, steam, and sometimes a small amount of liquid are forced out between the rubber gasket and the rim of the jar.

During this stage, the lid and rubber gasket, held loosely in place by the spring clamps, act like a one-way valve. They allow air and steam to escape, but prevent outside air or processing water from getting in.

As the jar cools, the pressure inside drops and a vacuum forms. At the same time, the higher external air pressure pushes the glass lid firmly down onto the rubber gasket, creating a tight, secure seal.

Adapting WECK Jars for Modern Canning

Firstly, after doing thorough research on WECK jars, we figured the manufacturer originally intended these jars to be used with open kettle canning. That said, we couldn’t quite understand how they’d work with inversion canning because the clamps on the lids tend to get in the way when you invert the can.

Because WECK jars were invented over 100 years ago – long before modern water bath canning became standard, we think they were originally designed so that the jar’s own mechanics would create the seal without any additional processing.

While that approach may have been sufficient in earlier home preserving practices, we personally felt more confident using a full water bath canning process for our preserves.

How to Can With WECK Jars (Without any mistakes)

The good news, canning with WECK jars is much like canning with Mason jars: you use the same canning methods – either atmospheric steam canning or water bath canning. The difference, though, is the jar itself. WECK jar comes with a glass lid, rubber gasket, and metal clamps, all of which add a few extra steps to get right.If you've only ever used Mason jars, learning how to can with WECK jars feels different at first. But, once you figure out the steps, the process is quite straightforward. The steps below cover the full process, from sterilizing, filling, sealing, processing, and all the way to testing, so nothing gets skipped.

Materials Needed  

• 1 glass Weck jar
• 1 glass lid
• 1 rubber gasket
• 2 metal clips

Step-by-Step Instructions 

1. Step 1: Wash and sterilize your jars. Same process as Mason jars (see our jar sterilization guide – link below).
2. Step 2: Remove the rubber gaskets from the glass lids and wash them separately in warm, soapy water. Once clean, place the gaskets back onto the glass lids and submerge the assembled lids in just-boiled water (off the heat). Leave the lids and gaskets in the hot water until you’re ready to use them, but for no longer than 10 minutes total.
3. Step 3: Fill your jars with preserve, leaving 1 inch of headspace.
4. Step 4: Using tongs, lift the glass lid and gasket from the hot water. Place the lid gasket-side down onto the rim of the jar. Secure it with two metal clamps positioned opposite each other. Press each clamp down firmly until it clicks into place on the jar rim. (see our Weck jar assembly guide ).
5. Step 5: Process jars in a water bath canner or atmospheric steam canner according to standard processing times. Since WECK jars come in different sizes and shapes than Mason jars, adjust processing times based on the closest equivalent Mason jar size.
6. Step 6: Carefully lift the jars out of the water bath and place them on a towel-lined surface, away from drafts or cold countertops.

   Do not touch, tilt, or reposition the jars while they cool
7. Step 7:

   Once the jars are completely cool, remove both metal clips. Gently but firmly try lifting the lid by its rim.

   If the lid stays firmly in place, the seal is successful. If it lifts or shifts, the seal has failed and the jar is not shelf-stable. In that case, refrigerate immediately or reprocess with a new gasket and lid.

   The rubber tab pointing downward is a helpful visual cue, but it should not be relied on as proof of a proper seal on its own. (See our WECK jar seal guide for more details.)

• • How to Safely Sterilize Mason Jars for Canning
  • Weck Jar Processing Time Guide

 

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Remember, WECK jars are European-made. Their sizes differ slightly from North American Mason jars. In line with the guidance of the National Center for Home Food Preservation, you might need to slightly adjust the processing time for these jars.

To make finding appropriate processing times easier, we created a handy WECK Jar Processing Time Finder. Simply enter your WECK jar style and size, and the tool will suggest the closest equivalent Mason jar so you can confidently follow trusted, tested processing guidelines.

How to check the seal on the WECK jar

As your preserve cools inside the WECK jar, take a moment to visually check the rubber gasket tab that extends slightly outside the lid. As the vacuum forms, you should see this tab gently pull downward, almost like a small tong. This is your first indication that the sealing process is working.

Once the jars have completely cooled, remove the spring clamps. You can then confirm the seal using what’s often called the lid-lifting test: gently try to lift the jar by the edge of the lid.

If the lid holds firmly in place, the seal is successful. If it lifts off, the seal has failed and the jar will need to be reprocessed or refrigerated immediately.

How to Open Sealed WECK Jars

One of the advantages of WECK jars is how easy they are to open. You don’t need, and in fact should not use, any tools like bottle openers or sharp objects to pry the lid off.

Instead, simply pull up on the rubber gasket tab. As you do, you’ll hear a soft hiss, which means air has entered the jar and the vacuum seal has been released. At that point, the lid will lift off easily and your preserve is ready to enjoy.

Watch how this is done in practice.

Frequently Asked Questions