If you’re looking for an easy way to store your favorite foods or drinks in the freezer, glass containers have probably come up as option. But is it actually safe to put glass in the freezer, or is there a chance it’ll break from the cold?
You can put tempered glass containers that don’t have ‘shoulders’ in the freezer without worrying about breakage. Make sure you leave enough space below the lid for the contents to expand, and leave some space between containers. Always let the glass cool down before putting it in the freezer.
Although many people use glass containers in their freezers, sometimes the glass does break. Let’s take a look at why that happens and if it’s really safe to use glass jars to store food in the freezer. We’ll also consider whether all kinds of glass can handle the low temperature, as well as some tips to freeze food safely.
Will Glass Break in the Freezer?
If you follow the right tips (we’ll get into them below), your glass container shouldn’t break in the freezer. However, breaks do occur in some situations.
For instance, if your container has either liquid or some other food with high water content, it might break because of the pressure exerted by the liquid present inside. This is because water tends to expand as it freezes.
Plus, not all types of glass are safe for freezing. For instance, non-tempered glass can break, while tempered glass is a much safer option since it’s much stronger.
Unlike non-tempered glass, it also doesn’t contain pockets of air that can contract and expand as the temperature changes.
Glass can also break in the freezer if it’s subjected to a significant temperature change in a short time period. For instance, if you put a slightly hot dish straight into the freezer, it might break.
Can Glass Jars Be Used to Freeze Food?
You can use glass jars to freeze food, provided that you take the necessary precautions. In fact, glass is preferable to many other storage options like plastic. There are several reasons why.
Non-Toxic
When it comes to storing food, one of the biggest concerns is toxins in the storage medium (like BPA in plastic) or cooking surfaces that can leech into your food.
That’s not the case with glass. And if you buy your jars from a renowned manufacturer, you won’t have to worry about toxins at all.
Scratch-Resistant
It doesn’t take long for a plastic container to get full of scratches. That not only takes away the aesthetics of the container, but it also results in small crevices that stain easily.
You don’t have to worry about any of that with glass, since it won’t scratch easily. You just need to make sure that you don’t break it.
Easy to Clean & Odor-Free
Glass is quite easy to clean — all you have to do is let it soak in hot water and then just wipe the surface. One reason for this ease of cleanliness is that glass is non-porous, so it doesn’t hold onto food particles very easily.
This is also why it doesn’t retain odors. In contrast, plastic is quick to absorb the smell of the contents that were previously present inside.
Inexpensive & Reusable
Another reason why glass jars are used for storing food in the freezer is that they’re durable and don’t cost a lot. Plus, since they’re long-lasting, reusable, and don’t wear down too quickly, the investment will be worth it in the long run.
Is All Glass Freezer Safe?
As a general rule of thumb, if a glass container or jar is oven-safe, then it’s also safe to use in the freezer, provided that you’re mindful of thermal shock (the sudden, rapid change in temperature that can shatter or crack the glass).
You can also safely keep mason jars in the freezer if you follow some precautions.
First, avoid the thermal shock we just mentioned. And second, keep in mind that liquids tend to expand as they freeze. So if you’re storing a liquid inside the jar, leave a few inches of space at the top to give enough room for the liquid to expand.
Also keep in mind that if you’re planning on freezing the jars for a long time, the gap present inside can result in the formation of freezer burn.
Drinking glasses are also freezer safe, but you shouldn’t put them in the freezer for too long. You can use a glass to store leftover milkshakes or smoothies for a few days, at most. Or you can use it to have a nice, refreshing chilled glass of your favorite beverage when it’s really hot out.
What About Pyrex?
Pyrex containers like these (on Amazon) are also safe to keep in the freezer, as long as you prevent thermal shock and leave some space at the top for the liquid to expand.
The good thing about Pyrex containers is that they have a rubber lid that allow for slight expansion, so you don’t need to worry as much about the space inside as you do when using mason jars.
Tips for Safely Freezing Food
As we’ve learned, glass can break in the freezer if you’re not careful. To prevent that from happening, here are the most important tips to keep in mind for safely freezing food in glass containers:
Let the Container Cool Down Slowly
When storing food in a glass container, make sure you warm or cool it slowly to avoid thermal shock and reduce the chances of the glass breaking. To do so, you can either let the contents cool down and then put them in the jar or put them in the jar and then let the jar cool down before putting it in the freezer.
Similarly, when you take the container out from the freezer, let it thaw for a while at room temperature without defrosting it with heat. This way, you can prevent the glass from breaking.
Don’t Use Shaped Containers
Mason jars often have “shoulders” — a curve near the jar’s top. Pressure can build up at these shoulders and eventually break the glass.
Any container with a similar shape can have such stress points. So when you’re looking for glass containers that you can put in the freezer, look for those that don’t have such shoulders or other similar stress points.
And if you have no choice but to use containers with shoulders, make sure you leave a good amount of space for the contents to expand. Doing so will reduce the pressure on the glass.
Make Sure There’s Enough Headroom
Liquids expand when frozen. So, when you freeze food, make sure there’s enough space (or headroom) at the top of the jar or container for this expansion. In the case of a mason jar, about two inches from the lid line should be enough.
Also, make sure you don’t tighten the lid completely when you first put the container in the freezer. You can do so once the contents are frozen (roughly after 24-48 hours). This will also help avoid pressure build-up.
Leave Sufficient Space Between Containers
Your glass containers can also break if they bump into each other. In fact, the containers can break more easily with the clinking of glass. To prevent that from happening, make sure to leave at least a little space between the containers.
With Pyrex, you don’t have to worry about giving too much space, since the rubber lids serve as a bumper for the glass.
Select the Right Glass Jars
Avoid using jars with a narrow top. Instead, go for jars with the widest neck you can get your hands on — like these wide-mouth mason jars from SEWANTA (on Amazon).
Similarly, don’t put glass with distinctive patterns in the freezer. This is because there’s a high chance that the design is not part of the jar and is attached separately. Such jars break easily when they’re subjected to a thermal shock.
The label on the jar or container will typically mention if the glass is safe to use in the freezer. So, if you choose the right jar, you don’t need to worry about it breaking or spoiling the contents.
Use Tempered Glass
Tempered glass is the safest option to use in the freezer. As we mentioned earlier, non-tempered glass has tiny air bubbles that make it more susceptible to breaking. But tempered glass is chemically treated to be stronger and handle high heat and cold.