How to successfully freeze in glass jars and containers – no more broken jars

One of my favorite things about the summer garden is the basil. We pretty much use basil for one thing….pesto. I shared photos of our first batch of pesto for this season and a couple of local friends asked me about freezing in glass jars. Then I got a comment on the post asking how to freeze in glass jars without the glass breaking. Apparently, I never got the “don’t freeze in glass” memo growing up and have been successfully freezing food in glass for most of my adult life. So, I thought I’d share my best freezing food in glass tips with you.

I also have some food preservation worksheets for you so you can know what freezes well and keep an inventory of what you have preserved. To get the worksheets, just fill out the form below and they’ll be emailed to you.

How to choose freezer storage containers

If you want to freeze food in glass containers you need to pick containers that are safe for freezing. That means that the glass is tempered, as non-tempered glass has microscopic air bubbles that will expand and contract when the glass is exposed to extreme temperatures as it is when canning, freezing, or baking.

Examples of tempered glass would be canning jars, freezer jelly jars, and glass storage containers that can be used in the oven (Pyrex® for example). Canning jars are my favorite to freeze in because they’re simple, inexpensive, and multi-purpose – you can freeze, store, and can in them. If you’re freezing baby food in jars, there is no need to get fancy (expensive) “baby food freezer jars“, 8 oz or 4 oz caning jar will do just fine. You can use the metal lids over and over since you’re not canning in them, however, if you wanted to use plastic you could get Tattler lids or plastic storage lids.

How to freeze in mason jars

I rarely break a glass jar in the freezer. I don’t have a good number but it’s just been a handful in 20+ years. Here are some tips.

1. Use jars without a shoulder if possible. So wide mouth jars, the tall pickle jars, and the regular mouth jelly jar above are great for freezing in.
2. Leave plenty of head space, especially if the contents have a lot of water such as broth. If the jar has a shoulder DON’T put the contents above the shoulder, stop filling before you get to the curve.
3. Label the contents. Frozen milk looks very much like frozen chicken broth – don’t ask how I know. But I now make sure to label everything. Just put a piece of masking tape on the lid and use a sharpie to write what the contents are on the lid. Do this before you put the container in the refrigerator.
4. Make sure the contents are completely cooled before you freeze them. I put the jars in the refrigerator overnight and then into the freezer the next day. This makes sure that they are cooled all the way through before they go into the freezer.
5. Don’t screw the lid on all the way until the contents are frozen. When I put the jars in the freezer the lids are just resting on the jar and after they’re frozen I screw the lids on all the way. If there is a lot of water, it will expand in the middle and will create a little hill inside the glass  jar. If the lid is on tight and you didn’t leave much head space, there’s no place for the liquid to expand into and the glass will break.

How to thaw food that’s been frozen in glass

The best way to thaw food that’s been frozen in glass is to put it in the refrigerator and let it thaw slowly. However, this can take a day or so and sometimes we need it faster than that.

When I need quicker than that, I’ll put it in the sink and fun hot tap water in the sink with the plug in. Don’t use boiling water, the key to not breaking the glass is to not go from one extreme temperature to another too quickly. If I’ve frozen the food in storage containers instead of jars, I’ll sometimes use the defrost option on the microwave. I check it and stir every few minutes. This is key.

What can you freeze in glass

Unless you have unlimited freezer space you’ll need prioritize what to preserve by freezing. There are a lot of things besides pesto that you can freeze in glass. I always can my jelly and jam but I know some people love the simplicity of freezer jam and jelly. If you don’t have a a pressure canner and want to make and preserve soup broth, freezing the broth is the way to go. Dried beans can also be cooked and frozen which is a great help for meal stretching. I actually like to put all the ingredients for hummus in the jar so when I thaw it out I can blend the whole thing and have fresh hummus in minutes. Although you could also blend the hummus and then freeze it. Hummus is the only thing I use tahini in so I like to make a several batches of hummus and use a whole jar of tahini so it doesn’t go bad.

I also use my freezer to store short term things such as eggs when we have too many in the spring so we have some in the fall.

I mainly use the rectangle storage containers for individual meals. When we have left overs, I’ll put them in meal size portions and freeze them for my husband and older boys to take to work for lunches. It works great if they have access to a microwave with most of them do.

Don’t be scared to freeze in glass, just follow these simple tips and it will all be fine. What do you like to freeze in glass jars?

Thanks for sharing with your friends!