If you’ve ever needed to quickly chill a warm drink in a glass bottle, you’re probably already aware that the freezer will do the trick. But if you happen to forget that you put your drink in there, you might end up with a shattered bottle.
Is this outcome due to the properties of glass itself, or could it be that the liquids freezing in the bottle are causing the glass to break?
While this represents a pretty specific example, glass is becoming more and more popular as a storage medium, whether storing foods in glass jars for long-term storage or in glass containers for short-term keeping.
In this article, let’s find out whether or not it’s safe to put your glass bottles and containers in the freezer, and what you can do to keep them from breaking.
Can Glass Go in the Freezer?
So, what’s going to happen if you put a glass container in the freezer? Well, that’s entirely dependent on a variety of factors, such as the contents and the initial temperature of the container.
To answer the question above, yes, glass can go in the freezer without concern for breaking, as long as certain conditions are met. Let’s take a look at these conditions next.
Why Does Glass Sometimes Break in the Freezer?
When done the right way, your glass containers shouldn’t break when frozen. Why then does this happen to so many people? Well, there are a few things that can lead to this.
The first, and most obvious, is the contents of the glass container. Unlike most things, water actually expands as it freezes. With that being said, if your container contains liquid (or foods high in water content), it might break due to the pressure put on it by the liquid inside of it.
Also, not all glass is recommended for freezing. While you might not run into any issues with non-tempered glass, it’s much safer to use tempered glass, when possible. Tempered glass is much stronger and doesn’t contain small pockets of air, like non-tempered glass, which can expand and contract with temperature fluctuations.
Another reason for glass breaking in the freezer is when a container is subjected to a rapid temperature change. For example, if you take a warm casserole dish and place it into the freezer, you’ll run the risk of breaking the casserole dish due to the significant change in temperature during a short period of time.
How to Keep Glass from Breaking in the Freezer
In the section above, I covered a few reasons why glass containers tend to break when frozen. Now, let’s take these observations and turn them into some easy-to-follow rules to use any time you freeze glass.
1 – Use Tempered or Freezer-Safe Glass
Not all glass is created equal. If you plan on freezing foods or liquids in glass jars or containers, always opt for tempered glass or glass labeled as freezer safe. As mentioned earlier, non-tempered glass contains tiny pockets of air, which can expand and contract as the temperature of the glass changes.
Tempered glass, on the other hand, is much stronger and can handle temperature changes just fine (assuming the remaining pointers in this article are kept in mind). Canning jars are typically safe for freezing, so either look for these, or look for something labeled as freezer safe.
2 – Leave Headspace
As I mentioned above, when water freezes, it expands. This is one of the most common reasons for glass breaks or cracks in the freezer. To protect against this, simply leave some room for expansion in your food container. This is often referred to as headspace.
By leaving a bit of space at the top of your container, the contents will simply expand upward, filling the empty space. Just be aware of the next tip as well…
3 – Don’t Tighten the Lids Immediately
When the contents of your container expand, they’ll put pressure on the air in the container as well. If you tightly seal your lid, this pressure will be put on the glass itself, potentially leading to a break.
To prevent this from happening, simply leave your lids loose on your containers until the contents are completely frozen. This could take 24 hours or longer, depending on the type and amount of food or liquid in your container. Once frozen, go ahead and tightly seal the lid.
4 – Avoid Containers with Shoulders
If you’re using mason jars for storage, which are very popular these days, look for ones that don’t have rounded shoulders on the top. Instead, look for ones that have straight sides with a nice wide opening at the top of the jar.
If you use jars with shoulders, just make sure you leave plenty of empty space for expansion below the beginning of the bottom curve of the shoulders. This way, when the liquids start expanding upward, they don’t run into more resistance (which is the issue you might face with jars that have shoulders).
5 – Change Temperatures Gradually
While glass can safely be put in the freezer, it’s important that you’re careful about how quickly the glass changes temperatures. Never put a warm glass container directly in the freezer.
If possible, first let your glass containers cool to room temperature. From there, place them in the fridge for several hours to cool even further. Once cooled, place them in the freezer.
When placing glass containers in the freezer, don’t put them near any freezing components, and don’t put them directly on top of other frozen items. This will subject the glass to too drastic of a change in temperature, which might lead to a glass break.
When thawing your frozen items, you’ll want to reverse the process by first loosening the lid, then putting the container in the fridge to thaw, then finally allowing the container to warm up to room temperature.
6 – Avoid Narrow Containers
The logic to this tip is similar to the one above about using wide-mouth containers. When the liquids in your container expand, they need room for the expansion. By using a tall, narrow container, the liquids near the bottom of the container need to work harder to expand upward.
A simple trick to increase the expansion area that seems to work well for a lot of people is to put your container slightly on it’s side in the freezer. By doing so, you’re giving the contents of the container a larger area to expand upward.
7 – Put Space Between Containers
The last tip for freezing glass cars or containers is to leave space between them. If you’re freezing several glass jars at once, don’t put them right next to each other in the freezer.
Instead, leave some “breathing room” between them to prevent any pressure changes from one container to have an effect on the containers sitting directly next to it.
What Are the Benefits of Storing Foods in Glass Containers?
Now that you know that it’s possible to store foods and liquids in glass containers in the freezer, let’s take a look at some reasons why you might prefer glass over other storage mediums.
1 – They’re Non-Toxic
When storing food, one thing you need to be concerned about are any toxins that can potentially leach into your food from the surface of the storage medium. The same goes for your cooking surfaces, such as pans and baking sheets.
People have become more aware of the chemicals found in plastic food containers, so you’ve probably noticed a lot of packaging that contains messages like “BPA Free.” As long as you buy your glass containers from reputable manufacturers, you don’t even have to worry about toxicity at all.
2 – They’re Easy to Clean
Another benefit of glass containers is that they’re relatively easy to clean. Simply let them soak in hot water for a bit, then wipe off the surface.
Because glass is non-porous, it won’t grab onto food particles. This results in a surface that’s easier to clean, and one that doesn’t retain odors.
3 – They’re Scratch Resistant
We have plastic food storage containers at home that are covered in scratches. Not only does this look bad, but it adds small crevices that tend to stain easily.
With glass, your main concern will be to keep it from breaking. You won’t have to deal with scratches, like you do with plastic containers.
4 – They Don’t Absorb Odors
As you’ve probably noticed, plastic storage containers often take on the smell of the foods that were previously stored in them. Those foods also often stain the surface of the containers.
With glass, you can easily clean the surface, and you’ll be left with a container that doesn’t maintain any odors from the items previously stored inside of them. This is due to glass being non-porous.
5 – They Stay Crystal Clear
While plastic containers may seem really convenient, one thing that’s not so great about them is that it’s difficult to see the contents inside of them. This only gets worse over time, as plastic often stains.
With glass containers, you can easily see what you have stored in them, making it more likely that you won’t simply forget about them and let them get buried in the back of your freezer. Also, because they’re so easy to clean, you don’t have the problem that you have with plastic containers where the surface gets cloudier over time.
6 – They’re Relatively Inexpensive
Glass jars have become very popular for food storage over the last several years, and with good reason. In addition to the other reasons already mentioned, they’re durable, and they can be bought in bulk for a relatively low cost.
When you factor in how long they last (more on that below), the cost of a pack of jars is even better than it may seem at first.
7 – They’re Reusable
One of the biggest benefits of glass is that it’s reusable. Unlike other types of storage containers that tend to wear down over time, glass can be used over and over again.
Also, as mentioned above, when glass is properly cleaned, it practically looks new and doesn’t carry over any of the odors from previous uses.
Because of the many benefits of glass, such as being free of harmful chemicals that can potentially leach into our foods, it’s an ideal storage medium to use. Although you’ve probably heard horror stories of glass breaking in the freezer, you don’t have to suffer the same fate.
As long as you take a few precautions, such as using tempered glass, leaving some room for expansion, and avoiding rapid temperature changes, you can safely and easily store your excess foods in glass containers in the freezer.