How to safely freeze liquids in mason jars
Canning, Freezing & More Preserving, Recipes

How to Safely Freeze Liquids in Mason Jars

It’s that time of the year when our freezers are probably seeing a lot of action as tomato sauces, vegetable soups, and all kinds of seasonal bounties start making their way from the garden to the kitchen to — eventually — this winter’s dinner table. A severe lack of space in my own freezer means I’ve skipped my old standby of freezing whole cherry tomatoes in favor of tomato purees that are ready to spice up for homemade marinara sauce, soup, and ketchup.

And that brings up a question I’m often asked: What’s the most ideal way to store these liquids in the freezer?

For years I used the flat-pack baggie method: fill a few zip-top freezer bags with liquid, squeeze all the excess air out, then lay them flat and stack them in the freezer.

While that tried-and-true method is pretty handy in the kitchen, these days I find myself reaching for my mason jars more and more. They’re easy to fill, easy to thaw, free of leaks, and useful for storing leftover liquids in the fridge (without the need to decant into a separate container).

And if you’re trying to avoid excessive use of plastic in the home, glass mason jars are a great, inexpensive option that you likely already have around.

But! If you aren’t careful, the glass can be prone to cracking or shattering in the freezer. So here’s a quick tip for making sure that doesn’t happen: use only straight-sided mason jars and fill them to the freeze-fill line.

Freeze-fill line on regular-mouth pint mason jar

On Ball and Kerr branded jars, the freeze-fill line is a thin line found just below the threads, about an inch from the rim. Some (though not all) jars even have “For Freezing — Fill Here” embossed on the line.

Freeze-fill line on regular-mouth half-pint mason jar

The purpose of the freeze-fill line is to indicate the maximum amount of liquid you can safely store in your jar without risking a cracked jar when the contents freeze and expand.

Freeze-fill line on wide-mouth half-pint mason jar

Jars that are best suited for freezing liquids include:

  • Regular-mouth jelly jar (4 ounces)
  • Regular-mouth jelly jar (8 ounces)
  • Regular-mouth jelly jar (12 ounces)
  • Regular-mouth half-pint (8 ounces)
  • Wide-mouth pint (16 ounces)
  • Wide-mouth pint-and-a-half (24 ounces)

You’ll notice that all of these feature straight sides. Jars with shoulders, such as regular- and wide-mouth quarts, are not suitable for freezing liquids unless you fill them to no more than 1 inch BELOW the shoulders. This isn’t the most efficient use of space, since only 2 1/2 cups of liquid will fit — but in a pinch, it’ll work. I’ve successfully frozen liquids in quart jars by making sure I leave plenty of headspace (about 3 inches) for the liquids to expand upward.

Fill quart jars to no more than 1 inch below the shoulders

If you aren’t comfortable with this, but like the convenience of jars and need to store more than jelly jars allow, you can also try plastic freezer jars. (These are great, and recent versions have better fitting lids than the previous Ball-branded versions.)

Here are a few things to keep in mind to reduce the risk of breakage with glass mason jars:

  • Glass can crack under thermal shock. Always cool liquids to room temperature before filling your jars.
  • Place your jars inside a cardboard box or other shatter-proof container before putting them in the freezer. This keeps other items from knocking into them, especially if you use a chest freezer. (These pretty storage boxes are perfectly sized for pint jars, and I especially like this genius JarBox protector — it’s kind of like an egg carton for jars.)
  • Don’t expose your frozen jars to sudden heat. Defrost them in the fridge, or out on the counter at room temperature.

What are some of your favorite foods to stash in the freezer?

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  • Dom

    Thanks, that was great. Awesome that a fill line is built in.

  • Alan

    Just bought my first jars, wanted to freeze homemade broth to make soup. Wanted to use quart size and understand about not filling to much because of breakage, and how quart size not good use because you can’t fill it up full with liquid, so my thought is to fill as you say, I think it was about 2/3 rds full, freeze, and then fill with veggies after liquid frozen. Just thinking outside the box, hope I don’t have any issues with freezing any jars.

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