Can You Freeze Glassware?
Glassware can be safely used in the freezer as long as you have taken the proper precautions.
Use tempered or borosilicate glass when possible, start with a room temperature glass, never one that is warm, and leave room at the top for expansion.
How to Ensure That Your Glassware Stays Safe In the Freezer
Check For The Freezer Safe Symbol
There will be a stamp on the bottom of most glassware indicating whether or not the glass is safe to use in the freezer. Below is the most common symbol indicating that a piece of glass is freezer safe.
Some symbols will be a snowflake indicating that the glass can go in the freezer. Others will have a temperature below the snowflake, indicating that the glass is safe to temperatures as low as what is listed.
Pick The Right Type Of Glass
Technically any glass can be used in the freezer, but the safest glassware is made of tempered or borosilicate glass and should be labeled freezer safe.
These glass types are more reliable because generic annealed glass has air pockets inside that can expand or contract, causing the glass to crack. Tempering the glass removes these air bubbles.
Borosilicate glass is lab-grade quality, so it can easily handle very low or very high temperatures.
Make Sure That The Glass Is Cool
If a glass goes from one temperature extreme to another, this is called thermal shock.
Some glasses like borosilicate glass can handle thermal shock very well, going from the freezer to the oven without a problem.
Still, most glasses will crack under this stress, so it is always safest to let your glassware slowly come up or down to temperature.
Leave Room At The Top For Expansion
Most liquids will expand when frozen, but what people don’t realize is that foods have moisture in them and grow.
Because of this, you need to make sure that you leave enough room at the top of the glass to accommodate this expansion.
Usually, 3/4 of an inch is enough room to allow any liquid to expand safely.
If you are very concerned about the glass breaking, some people also leave the lid off of the container as it freezes, screwing it on once it has completely frozen.
As the liquid expands, it can put pressure on the air sealed inside the jar. This extra pressure pushes on the glass and can cause it to shatter.
Any good quality glass should be able to handle this small amount of pressure, but if you’re using a generic annealed glass, then this extra step can be a good idea.
