Are you concerned about potential dangers of plastic? Think about switching your food containers to glass. This material is clean, safe to contact food, multifunctional and durable. Jars are decorative and stain-proof. However, does glass break in the freezer? Let’s check if the material is temperature-resistant and what are the precautions of safe glass freezing.
Types of Glass and Their Properties
Glass is a versatile, inorganic, solid material. It’s strong, recyclable and beneficially transparent. Glass is non-toxic, able to keep food fresh, nutritious and tasty for a long time. However, we use only the bottles and jars that are food-safe. Glass containers for freezing food are made of soda-lime glass that is classified as:
- Treated soda lime.
- Untreated soda lime.
According to the FDA, the glass should not contain any food additives, that is, leach no chemicals to the beverages. Meanwhile, chemical, optical and physical properties of glass determine its application.
Different Types of Glass and Their Uses
|Type of Glass||Thermal Shock Resistance||Linear CTE, at 68 °F, 10-6*K-1||Chemical Resistance||Applications|
|Soda-lime||low||8.5||average||containers to store food and beverages|
|Borosilicate||average-high||3.3||high||kitchen and laboratory glassware|
|Phosphates||low||9.4||low||medical, military, scientific|
Borosilicate (type I) glass is the most durable and heat-resistant. Except sand (silicon dioxide), borosilicate glass contains boron trioxide. This element is a poor conductor of low temperatures and electricity. Due to its application, the glass is resistant to thermal shock.
Freezer containers for soup made of this excellent material are microwave-safe. You may cook directly in the transparent cookware and then place it in a freezer. Par example, Pyrex bakeware is commonly made of tempered, borosilicate glass. It’s oven-resistant, dishwasher-safe, suitable to place in microwave or freezer.
What Temperature Does Glass Break?
Soda-lime silica glass is widely used for various household purposes. It’s utilized to produce:
- light bulbs;
- packaging of parenteral and non-parenteral preparations.
- beverage bottles;
- best containers for freezing food.
The material is made of lime (calcium oxide), soda (sodium carbonate) and sand. Due to simple, everywhere available components, glass is not expensive to manufacture.
It’s durable but prone to breaking due to thermal shock. Filled with chemically corrosive liquids, the glass bottles may degrade. However, being treated, exposed to sandblasting or thermal strengthening, it’s properties (strength and durability) can be improved.
Best freezer containers include the ones that are made of type II (treated) soda-lime glass. It’s tough, resistant to slow temperature changes. The jars withstand temperature up to 600 °F before cracking. However, will glass break due to extreme temperature change?
Can You Freeze Mason Jars?
Any jar or bottle is safely heated up to 300°F or even more. This way, they are sterilized before preserving seasonal vegetables or fruits. Sterilization is performed, using:
- boiling water;
- hot steam (steamer basket);
Difference in temperatures should not exceed 90°F (or 50°C). This rule is to be applied when you are going to chill food. Can I freeze glass jars? Of course, I do. Some safety precautions are to be observed, that’s all.
CTE or coefficient of thermal expansion is a parameter that is not too intuitive to understand. It shows how much the jar size changes when the temperature drops. If its volume contracts suddenly and significantly, the object may crack.
How to Select Best Containers for Freezing Individual Meals?
Quite naturally, it’s essential to select a suitable, freezer-safe container. Jars, made of tempered or borosilicate glass, have the lowest coefficient of expansion. They survive thermal shock easier.
Additionally, borosilicate resists chemical and moisture attack. This material won’t break during a power outage. The surface virtually doesn’t interact with acids and alkalis. However, after prolonged exposure, surface erosion and graduation destruction may occur.
How long can a glass bottle stay in the freezer? Besides material, it depends on its:
Wide-mouthed, straight-side jars are preferable. They are much more stable than the ones with shoulders. The bottle should not be overfilled. When liquid inside expands in a freezer, it finds the way out. Glass crack or breakage should not become the only possible outcome.
Thick glass is less fragile. Additionally, your jar is to be as new as possible. It still degrades in some years of heavy use.
Tips to Freeze Canning Jars Safely
Following the guidelines, avoid breakage. Going to freeze soup or meat in a glass container:
- leave 1-2-inch headspace above the food level;
- chill the container up to the room temperature before freezing;
- don’t put the glass on an icy surface;
- cover the liquid by plastic wrap or aluminum foil until it becomes solid;
- put the lid loosely;
- don’t let the jars touch each other in the freezer.
How long does it take for something to freeze? It this case, take your time. Rapid freezing in glass containers is not recommended. Why? It may cause thermal shock. Better wait until the temperature difference is as small as possible. Wrap the jars by paper towels. Separate them by cardboard. Leave some space between them or place the jars on different shelves.
So, can you put glass containers in the freezer? Yes, it’s quite safe. Just select a top-quality, freezer-safe item. Fill it not full of food and wait until it cools down. Prevent significant thermal shock. It lets you preserve your dishes safely in non-porous, chemically-inert glass containers.