I’m all for batching my cooking. Not only does it save time and money, it’s also nice to have a stock of homemade goodness in the freezer ready to go whenever you want it.
One problem, however, is storage. Plastic is something I’m seriously trying to phase out as much as possible, which raised the question that spawned this post – Can you freeze Mason jars and other glass containers?
Thankfully, the answer is, Yes, you can!
There are, however, one or two things you need to know when freezing Mason jars if you want to avoid cracked and broken receptacles. Most of the tips are common sense and all are easily achieved and practical, so you can dramatically reduce the amount of breakages with the minimum amount of effort.
First, though, let’s take a look at a few other points regarding glass freezer storage containers and what you can keep in them.
Choosing the right glass container for freezing
Choosing the right glass container for freezing is one of the most important parts of successfully saving your delicious dishes for another day. Some things to look out for include:
Straight edges, not shoulders
When it comes to freezing Mason jars, selecting the wide mouthed variety is always the best way to go. Freezing jars with shoulders can be done successfully, but you will need to take a lot more care not to overfill them (more of which later).
Straight-sided, wide mouth Mason jars are a lot more stable.
Why is this? Well, liquids expand when frozen, and the only way they can go in a glass jar is up. So, if your Mason jar has a shoulder and its contents have already reached sufficient enough solidity whilst freezing, a crack or complete breakage is the only likely outcome.
With this in mind, jars or containers that have weird curves or bulges below the liquid line will likely be fine, so long as the glass container’s neck or upper portion is relatively straight or flares outwards rather than in.
There’s no real hard and fast rule when it comes to how thick glass should be for freezing. Thicker glass jars and containers are generally deemed to be better, but even those can be broken easily if mistreated or the simple rules of freezing neglected.
Age can also affect glass when freezing. Older jars and containers will be far more likely to break than newer ones will, so replacing your glass receptacles regularly is good practice if you want to keep breakages at a minimum.
Glass types suitable for freezing
This is relatively straightforward, but worth including. If you intend to freeze glass, you should only use containers that have been tempered or have been listed as “freezer-safe” by the manufacturer.
As more and more of us switch to glass instead of using plastic, manufacturers are naturally keen to point out that their glassware is freezer-proof, so it shouldn’t take too much searching to find the proof you need.
Tempering glass toughens the substance up and allows it to withstand treatment that “normal” glass simply couldn’t handle. (1)
It’s commonly used when canning foods for distribution, which brings us nicely to…
Can you freeze glass jars you’ve saved?
Yes. As mentioned above, foodstuffs purchased in glass jars at the store are made from tempered glass, so they would be suitable for freezing. This is great for two reasons: they are effectively “free” and you’ll be reusing something that would otherwise have to go through a recycling process.
I do, however, have to add some sort of disclaimer to this: If you choose to recycle glass jars in this way, you are doing so at your own risk. It is far more advisable to purchase Mason jars labeled as freezer-safe rather than taking a chance with an old jar.
A downside to reusing old food jars from the store is that the lids generally aren’t the best once they have been “popped” open. Personally, I prefer a solid twist when sealing up certain foods, especially liquids, but this is more to avoid leaks once they’ve thawed out than anything to do with the freezing process.
So, what lids are best for freezing? Well…
Which lids work best when freezing food?
For the actual freezing of foods, all you really need is a tight enough seal to keep air out of the container. Freezer burn can ruin food fast, so an airtight seal is essential.
The key thing to look out for is the little sealant ring on the inside of your lid where it’ll meet the top of the jar. If there’s one present, and it is free from scratches, scrapes, or other marks that may impact its integrity, it’ll be good enough for freezing purposes.
While metal lids are great for freezing, plastic lids, such as these by iLIDS, work perfectly well, too, and the different colors available are handy for quickly picking similar looking foods from your freezer without the need for labeling.
If you do decide to use plastic lids for your Mason jars, though, please make they are BPA free before purchasing.
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What can you freeze in glass jars and containers?
Pretty much everything you would put into other containers can be frozen in glass. Some of the things you might find in my freezer include:
- Pasta sauces
- Apple sauce
- Smoothies (yes, you can freeze smoothies in Mason jars!)
- Cooked legumes
- Almond milk
Another fantastic thing to freeze is baby food. Prepping ahead and freezing baby food can provide your little one with nutritious meals at all times…who wouldn’t want that?
Tips for freezing Mason jars
Freezing food in Mason jars and other glass receptacles isn’t rocket science, but you do need to adhere to a few tips if you want to minimize breakages.
We’ve already seen how the type of jar and its age can affect how it will stand up to freezing, but what else should we be doing to prevent Mason jars cracking in the freezer?
Use freezer-safe jars
Let the eye-rolling commence!
I know, it’s obvious and I’ve already mentioned it, but using jars that aren’t fit for purpose is the quickest way to end up with a freezer full of cracked or, worse still, broken glass.
Check the packaging before you buy your Mason jars to ensure they can be safely placed into the freezer. For example, Ball’s pint-sized wide mouth Mason jars are freezer safe, but their quart and half gallon jars aren’t.
See the section, “Glass types suitable for freezing”, above for more on this.
Leave some room
As I’ve already touched upon above, certain foods will expand when frozen. These are typically those that are more liquid, like soups, for example.
So, in order to stop your Mason jar cracking in the freezer, it’s absolutely vital you leave a little room between the level of the food you’re freezing and the top of the jar. This gap will allow your food to expand upward without breaking the glass.
How much space should you leave? Well, that kind of depends upon the type of container you’re using and what you’re freezing.
If you’re using a quart wide mouth Mason jar to freeze cooked chickpeas without liquid, you won’t need to leave any gap whatsoever. Freezing pasta sauce in exactly the same container will, however, need at least 1.5 inches to be on the safe side.
Using jars with shoulders changes things again. For this type of receptacle, you need to leave the same gap you’d leave with a wide mouth jar, but this time up to the level where the shoulder begins, rather than the top of the jar.
A good rule of thumb when using glass containers for freezing is to leave more room than you would ever think necessary. Then, once the food is frozen solid, you can examine just how much it has expanded and adjust accordingly next time around.
To do this, you can either mark the level with a marker pen or, if you don’t like to put ink on your favorite jars, put a slim colored rubber band around the jar and roll it up to the pre-frozen level to give yourself a removable marker. Simple.
Chill your food first
Before you put your food filled Mason jars into the freezer, it’s always a good idea to properly chill them first. Doing so is easy: just pop them in the refrigerator for a couple of hours before switching to the freezer.
Naturally, if you’re dealing with red hot soups, sauces, or, most importantly, jams, you should allow them to cool before decanting into the jars themselves anyway, but taking the temperature down further by refrigerating them as well will help prevent breakages in the freezer.
Why? Well, thermal shock (a sudden change in temperature) can cause breakages, so cooling things right down will add another layer of protection when freezing Mason jars. (2)
Don’t use jars with shoulders when freezing
I’ve already gone over this above, but in case you’ve skipped to this section it’s worth reiterating; it’s probably the most important tip for freezing Mason jars.
Back up a bit and read the section titled “Straight edges, not shoulders”.
Leave the lid off (or put on loosely)
Another way to stop the expansion from cracking your beloved Mason jars is to leave the cap off while the food freezes. Doing so allows the air to escape as the food expands in the jar, instead of putting pressure on the glass.
Once the food you are freezing is frozen solid, you can put the lids on and gently tighten them up.
Separate the jars with cardboard in the freezer
If you bought your Mason jars in a box of six or 12, the cardboard separators (the criss-cross, tic-tac-toe style matrix) that they ship with is ideal for this. If not, any sheets of cardboard cut to size will do the trick.
The key is to keep your jars separate and not touching, so you could even simply leave gaps between them. However, I don’t know about you, but whenever I try this and close the freezer drawer, whatever is in it seems to come to life! They always slide all over the place and end up bunched together in one corner, which isn’t what you want when dealing with glass in the freezer.
Another option is to put your jars in socks before freezing, but this can make the bases a little unstable. Clean socks only, please, if you go down this route!
Freeze in usable portion sizes
This is more of a general freezer tip than one that’ll protect your jars, but it’s worth keeping in mind.
Whenever you freeze food, try and separate it into usable batches. Putting enough soup for six into one container when you intend to eat alone is never a good idea!
Thawing food frozen in glass jars
We’ve already touched upon thermal shock earlier and how susceptible glass is to sudden changes in temperature, so it makes sense to use the gentlest thawing method possible when dealing with glass containers.
By far the best method for defrosting food stored in glass is to simply remove the jar from the freezer and place it straight in the refrigerator. This will allow the food to thaw slowly over time, which will not only help minimize the amount of breakages you have, but also preserve the texture and flavor of the food much better.
Thawing food in the fridge can take a while, however, so you might want to speed things up a little if you’re pushed for time. One way to do this would be to just let the jarred food thaw on the counter rather than in the refrigerator.
You may read elsewhere that you can plunge the jar into warm water or use a warm oven to quicken the thawing process, but I would strongly advise against these methods when dealing with glass. You may get away with it, but by using these methods of defrosting you are increasing the chances of breaking your glass jars exponentially.
Using other glass freezer containers
If you know in advance that you’re going to need to thaw something fast, how you freeze it can make a big difference. Instead of using jars, try using a flatter, shallow, tray-like glass receptacle. Doing so will increase the surface area of the food, which will make thawing a whole lot easier.
Be warned, though. The greater the surface area, the higher the risk of freezer burn, so make sure you use foods frozen in this way sooner than you ordinarily would if it were stored frozen in a jar.
Can Pyrex go in the freezer?
One of the most popular brands of kitchen glassware is Pyrex, so it stands to reason that many of you have asked the question, Is Pyrex freezer proof?
The answer is, Yes, Pyrex is safe to use in the freezer, but it isn’t indestructible, though. While Pyrex goods are indeed made from a very strong material – low-thermal-expansion borosilicate glass – it is still possible to break them.
The best way to treat Pyrex is like any other type of glass: with care.
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Can Pyrex go from freezer to oven?
Another common question is, can you put cold glass in the oven? Usually, this would be an automatic No!, but rephrasing it slightly to Can Pyrex go from freezer to oven? gives you a different answer.
You can put Pyrex straight into an oven from the freezer, but there is a specific thing you need to remember before attempting it: never put Pyrex straight from the freezer into a HOT oven. While it is designed to resist thermal shock, it’s still worth erring on the side of caution.
- 24-PIECE SET: Includes (3) 4-Cup, (3) 2-Cup, (3) 1-Cup round containers with lid, and (3) 3-Cup rectangle container with lid. These containers will help you store your food safely while saving space.
- HOUSEHOLD ESSENTIALS: Life can get hectic and messy. This Pyrex set is meant to take the burden off your shoulders when it comes to food storage and meal prepping. With a diverse range of sizes, you can be flexible with the way you manage your meals.
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- PERFECT LID FIT: Plastic lid fits snug over glass container to keep your food fresh and tasty. The colored lids make for a nice, bright touch to your storage.
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So, with this in mind, put your frozen Pyrex dish into the oven before you turn it on. This will allow the borosilicate glass to warm up slowly rather than being subjected to high temperatures whilst still frozen.
While putting your Pyrex dishes into the oven from the freezer may be convenient, I still prefer to plan ahead and thaw the food thoroughly before reheating, but yes, you can put Pyrex straight into the oven from the freezer in a pinch.
Think minimizing breakages, not eliminating
Who knew such a seemingly small question like, Can you freeze Mason jars? could result in a post of this length?!
Well, now we’re finally done, I wanted to leave you with a quick warning…you may well still experience breakages no matter what preventative measures you use.
Glass is a delicate material, so all we can do is our best to ensure that cracks and breaks are kept to a minimum. Be careful with it, stick to the tips above, and you’ll be able to use your glass jars in the freezer time after time…probably ?
Regardless of the hassles and trauma of finding broken jars in your freezer, glass is still the way to go. Plastic has such a detrimental effect on the environment and the impact it can have on our own health is still not entirely known, so make the switch to glassware for your freezer as soon as you possibly can.
If you have any other tips or questions on freezing glassware, please drop me a line in the comments below.
About The Author:
Lisa Williams is a committed vegan, passionate animal welfare advocate, and keen follower of too many v-friendly food blogs to mention. She started happyhappyvegan.com back in 2016 because she felt there was a need for more straightforward information on plant-based living.
Back then, too many sites seem to either concentrate solely on recipes or be too intimidating or inaccessible for the v-curious, and she wanted to change that. The landscape is certainly a whole lot different now!
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- Mark Ford | How is tempered glass made? | https://www.scientificamerican.com/article/how-is-tempered-glass-mad/
- CorrosionPedia | Thermal Shock | https://www.corrosionpedia.com/definition/1079/thermal-shock