Mason jars are some of the most useful items to have at home. Mason jars are great for decoration, and an excellent replacement for plastic containers.
Plus, mason jars are readily available basically anywhere. You can even reuse some of your grocery jars, provided they are made from tempered glass (more on this in a bit).
Although originally made as a canning jar, this type of jar has a wide array of household uses that you may be surprised about. And, yes you can freeze mason jars!
Moreover, don’t get any wrong ideas. Your mason jar won’t shatter to pieces should it break in the freezer, it’ll likely crack and fall apart in a couple of large chunks.
Even so, it’s still unfortunate to let go of that batch of vegetable broth you’ve been saving up scraps for! With these easy-to-follow tips we have on freezing your mason jars, you’ll never have a jar break on you again.
Why Do Mason Jars Break In The Freezer?
The main reason a frozen jar can break is because of thermal shock. Namely, when your jar goes through a swift shift in temperature.
Thermal shock, by definition, is a “mechanical load caused by a rapid change of temperature.”
This is typical when, for example, you take a recently finished dish from room temperature (but boiling) and stick it into a mason jar and into the freezer.
Even high-quality glass should not be subject to such rapid temperature changes.
Additionally, if you do not give enough space to the content of your mason jars, they are likely to shatter, but more on that in a second.
How To Put Mason Jars In The Freezer
Let the Contents Cool
To freeze glass jars properly, you have to first let the contents cool.
Never transfer food straight from the stovetop to your mason jar and then to the freezer without letting it cool first. That’s just a recipe for disaster.
Remember that the main reason for broken glass when freezing is thermal shock. Well, this is exactly what we mean.
Without letting the contents adjust to room temp before putting it in the freezer, you’re risking rapid changes in temperature that may cause glass jars to break.
If you want to be completely careful, you may opt to let the contents cool down (in or out of the jar) to room temperature, stick it in the fridge overnight, and then put the jar in the freezer. This way, you’ll be able to modulate the temperature much better.
Choose the Right Mason Jar Shape
You want to make sure that you have straight sided mason jars or wide mouth mason jars. Mainly, you want to make sure that the jar does not shift shape from top to bottom.
In case you do not know the difference between straight side jars or ones with shoulders (where there is a shift), we’ve got you covered below.
If you do not have the right glass containers and the only ones available at home have shoulders, you can still manage.
The main reason why many people avoid using quart jars when freezing liquids or food is that it takes up a lot of space in your freezer. In a further section on headspace, we explain the value of leaving space for your liquids to expand.
In a mason jar with shoulders, you will need a much larger space for the liquid to expand since you need to start marking from the shoulders, not the cap.
If you have an upright freezer, you likely value space a lot, so choosing wide mouth mason jars is your best option for freezing in glass.
Choose the Right Type of Glass Jars
The type of glass you use is essential to freezing food. Freezing in mason jars that are not the right type of glass makes it that more likely to suffer from temperature changes and broken glass.
What you want in this regard is tempered glass.
Essentially, tempered glass is a tougher version of regular glass; it is specifically manufactured to be more robust than regular glass.
A glass that is not tempered usually suffers from air bubbles(at a very miniature level) when it goes through temperature changes.
These changes can eventually lead to broken glass.
Mason jars such as ball jars are most likely made from tempered glass. Unfortunately, the glass containers from your groceries like spaghetti sauce jars might not be the right fit.
To be fair though, you can still use non tempered glass for freezing food. However, they aren’t guaranteed freezer-safe and these types of glass jars break far easier than the tempered options.
If you take all the necessary precautions such as cooling properly before freezing and leaving enough space (see next step), you might be successful.
To freeze mason jars; let the content cool down, choose straight jars with tempered glass, and leave sufficient space on top.
Leave Sufficient Space At The Top (headspace)
Make sure you leave ample space at the top of your container regardless of the type of jar that you freeze.
For both types of jars, you will want between 1 to 2.5 inches(this is also known as headspace). The difference lies in when you will apply this space.
For the shouldered jar, the space should be below the shoulders. For the straight jar, do your measurements from the top.
The reason you need to leave space at the top is that when food freezes, it expands. Another major reason for frozen jars breaking (aside from rapid temp changes) is the lack of space for the liquid to expand.
Although broken jars don’t really explode at the touch, not leaving enough space could result in a cracked jar that ultimately leads to breaking glass.
You can find plenty of measurements online about the headspace you should leave for jars. The point is, leave space at the top; the bigger your jar, the more space you should allow!
Some mason jar brands such as Ball and Kerr also have a fill line on their wide mouth jars. You can use those as a basis for how much food or liquid the jar can take.
If you still have some doubts about the space you might need, you can also try to freeze the mason jars without a lid first. That way, you can let the liquid expand without the tight limitation of metal lids.
Once you’ve left it in your freezer for some time, you can put the lid on.
Another solution for your mason jar is to place your glass jar in your freezer sideways.
The logic behind this technique is that placing the jar horizontally allows the liquid to flow through the entire length of the glass jar. This effectively creates more space than putting it upright.
If you don’t have a chest freezer and space is an issue, you can put it sideways in the first 24-48 hours, and then switch it back upright once it’s already frozen.
If that is not enough, then you can also make sure the lid is not too tight.
By keeping the cover of your mason jars a bit loose, you make sure that there is a bit of air that can get out as the food or liquids inside expand.
While this may sound obvious, make sure you keep the mason jars away from the cooling side of the freezer. Near the freezer door is a good place to start.
What Can You Freeze In Mason Jars?
Freezing food is an excellent way to preserve produce and make large-batch cooking last longer. But although we might have made it sound like you can only freeze liquids in a mason jar, that’s not the case at all.
You can freeze any fluids or solids. Typically, for glass freezer containers, you’ll see anything from soups and homemade broth to fruits like berries and bananas.
However, our earlier tip about leaving some space in the container is even more critical in terms of liquids.
The logic is simple; if you fill a jar with fruits and freeze it, there will inevitably be small pockets of space, allowing the fruit to expand when they freeze.
However, if you apply the same logic to liquids, keep in mind that you will not have these pockets of air space. So be extra careful with liquids.
Liquids tend to be the most common example for freezing food with a mason jar because of their efficiency. If you want to freeze fruits without turning them into a puree or a jam, then freezer bags might be the better option.
Other Tips
- If you plan to leave more than one mason jar in your freezer, it would be a good idea to label them. We recommend you use washi masking tape and a permanent marker, making the perfect glass freezer container. Make sure to include what the contents are as well as the date of preparation.
- Be careful with storing the canning lids of your jars. It is quite common to see that the lids of your jars rust. This happens because of where you store them, namely in a humid place, near the sink. What you want to make sure of is to keep these lids in dry areas; and above all, avoid plastic lids.
- If you are using a chest freezer, we highly recommend using a cardboard box to store your jars. The frozen items in your freezer might collide with your mason jars and inevitably result in cracked jars. With a separate container, you can organize the jars properly and prevent damage.
- When thawing your frozen food or liquids, make sure to distinguish one from the other. You can simply shake fruits, for example; but for liquids, we suggest letting them defrost slowly outside of your freezer. Either way, it would be best to take the frozen jar from the freezer and let it defrost gradually. First, in your refrigerator for a few hours, and then at room temperature if necessary.
Final Thoughts
So, can you freeze mason jars? Definitely. And we recommend you do!
Mason jars are the way to go when it comes to glass jars containers to have at home.
Whether you want to freeze broth, whole fruits, or soup, you can do a lot of your food storage with these glass jars.
There’s a reason they are one of the most famous Zero Waste Swaps promoted.
These jars are suitable for both liquids and solids. Moreover, mason jars are great for decoration in any way. So if they’re out of the freezer, you can still use them to spice up your home.
As long as you know how your freezer works and how to freeze your jars, then you should be able to avoid broken glass just fine. Remember, jar breakage isn’t normal. There’s a right way to freezing your mason jars to avoid any accidents.
Also, do not forget to avoid plastic lids (or any plastic for that matter) as much as possible. It might be convenient at the moment but the environmental cost of those plastic lids is far too high.
Feel free to reach out to us with any comments or questions.
