I’d been freezing glass jars for the longest time, but too often, I’d open the freezer to disappointment: yet another precious mason jar cracked and broken, even though I thought I did everything right.
But after researching why it kept happening, I discovered I wasn’t doing everything right. And when I started following five simple rules, I stopped finding broken jars.
Why Freeze in Glass Jars, Anyway?
Keeping your freezer filled with homemade broth, sauce, and soup is a fantastic way to keep your home stocked with healthy convenience food. But after stewing, brewing, and cooking all that nutritious food, you need a simple, non-toxic way to store it.
Here are the most common options:
- Plastic containers can work fine in a pinch, but plastic food storage can leach chemicals.
- Pressure canning broth or soup in glass jars is another option but requires more work and attention.
- Filling up a glass jar of your favorite Avocado Ranch Dip and popping it in the freezer, though? Now that’s a whole lot simpler. And we like simple around here!
But Here’s the Problem With Freezing Glass Jars
Unfortunately, it’s really, really easy to end up with broken jars if you aren’t careful.
So I did some legwork to research the best tips for freezing mason jars and other glass and consulted folks who’ve been freezing glass longer than I’ve been alive.
The next time you’ve got a batch of broth or a double recipe of soup to freeze, follow these simple steps and enjoy a freezer full of food in unbroken glass jars!
Disclosure: I’ve included affiliate links in this post for products that can help you freeze in glass jars more easily. Your cost through these links is never increased though I can earn a commission on purchases. Thanks!
5 Simple Tips for Freezing in Glass
1. Play It Cool
Make sure to cool your broth, soup, or sauce before ladling it into glass jars, then completely cool the jars in the fridge at least overnight before freezing. (If you can manage to cool them 24 hours first, even better!)
This does two things:
- It won’t shock the jars when you fill them with liquid (that means giving the jars such a huge temperature change that the glass shatters), and
- You won’t burn yourself by ladling hot liquid into jars and spilling on yourself. Not that such a thing could ever happen in my kitchen. (Bonus tip: This wide-mouth funnel is my new favorite kitchen tool for avoiding a mess!)
2. Leave (More) Room
This is an easy mistake to make and was my biggest mistake in the past.
I used to leave 1-2 inches of headspace in the jars when filling them up with broth, thinking there was plenty of room for the liquid to expand while freezing. But most of them would still break and crack. I was stumped.
Turns out that it isn’t the top of the jar you need to be mindful of when filling your jars. It’s the shoulders.
Any time you freeze in a glass jar that has shoulders, you have to make sure the broth stays below the shoulders while it freezes and expands. That means the broth should be 2-3 inches below the shoulders before you stick it in the freezer.
3. Rethink Your Glass Jars
Instead of using regular glass jars and worrying about the shoulders, you can use wide-mouth mason jars.
Bonus tip: Many brands of organic or natural peanut butter are sold in wide-mouth glass jars, which are perfect for freezing smaller amounts of broth! You can even get the labels and adhesive off the jars when repurposing them with this simple 2-ingredient cleaning paste.
These wide-mouth jars are the best for freezing broth, sauce, and soup. Since they lack the shoulders that most jars have, the jar isn’t put under pressure when the broth freezes and expands. I don’t have many of these, but I do reach for them first when I go to freeze broth.
One reader even told me that they stick warm broth right in the freezer in wide-mouth jars with nary a glass casualty.
4. Keep It Loose
When you tightly cap jars before freezing, they tend to break more often. If you just loosely place the lids on until the broth is totally frozen, the jars hold up better. (These BPA-free plastic lids are especially handy when storing food in jars, or they come in pretty colors here.)
Once the broth is frozen, you can tighten the lids if you remember. It’s not a big deal if you forget, though. I rarely think to do it, and my frozen food never gets freezer burn!
5. Avoid Touching
Jars that are touching when placed in the freezer seem to break more readily, as well. This problem has another simple solution: just leave a little space between the jars when placing in the freezer.
Bonus Tips for Freezing in Glass Jars
Many kind readers have contributed their wisdom about freezing glass jars in the 250+ comments below, so give them a scan if you want more ideas! Some of my favorites:
- Place your jars in a cardboard box (like the one mason jar sets are sold in) before putting them in the freezer. This allows you to easily keep some distance between them and can also be handy if you use a chest freezer. Or use a JarBox, a genius product!
- Slip your jars into clean socks before putting them in the freezer. This prevents them from bumping against each other and breaking that way.
- Try Glasslock storage containers. The glass is tempered, so it’s stronger and better able to handle temperature changes. They are pricier than canning or repurposed jars but might be an investment you’d like to make since you can also cook with them.
- Stick with jars that are designated as freezer-safe, like these pint-and-a-half wide-mouth jars, or use smaller size jars like wide-mouth pint, half-pint, and 4-ounce.
Frequently Asked Questions About Freezing Glass Jars
Below, you’ll find helpful answers to the most common questions about freezing in glass jars:
- Can you freeze soup in mason jars? What about freezing broth in glass jars? Go to answer
- Help! My glass jar cracked in the freezer. Is there anything I can do to salvage the food? Go to answer
- Are there any special tricks for how to thaw or defrost a frozen glass jar? Go to answer
- How do you label frozen jars? Go to answer
- Are all glass jars freezer-safe? What are the best jars for freezing? Go to answer
- My mason jar lids tend to get rusty after freezing, thawing, and freezing again. What can I do to fix it? Go to answer
- I followed all these guidelines, but my mason jar cracked in the freezer. What did I do wrong? Go to answer
Can you freeze soup in mason jars? What about freezing broth in glass jars?
Yep! You can freeze soup, broth, sauce, and more in glass jars. Here are a few of my favorite recipes that I freeze regularly:
Help! My glass jar cracked in the freezer. Is there anything I can do to salvage the food?
Unfortunately, I’m afraid not. After a glass jar cracks, some shards of glass can make their way into the food, so it wouldn’t be safe to eat. Also, if you open the jar, it can explode, sending glass and food splatters everywhere! To be on the safe side, put that broken jar in the trash and make a plan to follow the tips in this post from here forward.
Are there any special tricks for how to thaw or defrost a frozen glass jar?
To avoid broken jars during the thawing process, follow these tips:
- Loosen the lid or remove it entirely.
- Move the jar to the back of your fridge to start thawing.
- When the liquid seems mostly thawed, you can move the jar to your kitchen counter to continue thawing.
- Do not put the jar in hot water or in the microwave to thaw. Because if the jar itself isn’t yet at room temperature, the thermal shock could crack or break the jar. (I’ve heard of some folks putting frozen glass jars in the microwave on the defrost setting, but I try to avoid this because microwaves don’t heat evenly, and the glass could crack because of that.)
- To defrost more quickly, you can put the frozen glass jar in a bowl of cold water. (Never hot water!)
How do you label frozen jars?
Here’s what I do: Put a small piece of masking tape on the lid of the glass jar, then use a marker to write the name of what’s inside and the date I made it.
Are all glass jars freezer-safe? What are the best jars for freezing?
Most mason jars these days are made of tempered glass, which means the glass is several times stronger than regular glass. However, many foods you buy in glass jars like jellies, pasta sauces, and so on are not tempered glass and therefore will be more likely to break in the freezer.
My mason jar lids tend to get rusty after freezing, thawing, and freezing again. What can I do to fix it?
Some of my friends swear by these BPA-free plastic screw caps for mason jars. But if you’d like a plastic-free solution, you can add small pieces of wax paper under the mason jar lid (square pieces or cut into a circle if you want!). As a bonus, your jar lids will stay clean.
I followed all these guidelines, but my mason jar cracked in the freezer. What did I do wrong?
Sometimes glass jars just break! If you’re using a repurposed glass jar, it could be that the glass wasn’t as strong as you might find in a mason jar. Or it’s possible that the jar already had a small crack in it, such as if someone dropped it in the sink while washing it or if two jars got clanked together in the kitchen.
Replace that jar, keep following the steps outlined in this post, and you’ll wildly decrease your chances of it happening again.