Mason jars are an essential in any kitchen. They’re ideal for anything from canning to storing leftovers! But can Mason jars be microwaved? Yes, but with a few qualifications. Newer Mason jars are almost always made of microwave-safe tempered glass. If the Mason jar is new or has a microwave-safe symbol on the bottom, it is safe to use with heat. Microwaving older Mason jars is not recommended. What is the reason for this? Continue reading to find out how to tell if a Mason jar is microwave-safe and how to use them safely and effectively in the microwave!
Microwave-Safe Glass Vs Regular Glass
You might recall this from high school physics class: glass expands and contracts in response to changes in the environment’s temperature. In other words, the glass actually contracts when it is cooled or frozen. It will expand as it gets hotter. The rapid expansion or contraction of the glass can actually cause it to crack when the cooling or heating process is too abrupt or drastic.
Regular glass should never be placed in any of these appliances because the temperature can drastically change there, including the dishwasher, microwave, and oven. Of course, engineers have now discovered a solution to this problem. Due to this, tempered glass is a thing of the present (also known as safety glass).
Extreme heating and quick cooling are used to manufacture safety or tempered glass. Tempered glass is much harder than regular glass as a result of this process, making it less likely to break when the temperature changes around it.
Regular glass will crack when exposed to consistent heat above about 350°F, but tempered glass can withstand temperatures of up to 1,100°F. You don’t need to be concerned about the glass shattering in the oven or microwave because heat-safe glass that can be used in both is made of tempered glass.
Tempered glass, however, can deteriorate over time. Even if you are aware that the glass is oven-safe, it is best to stop using it in the oven or microwave if you notice any cracks in the glass.
Can You Microwave Mason Jars?
Yes, provided that your Mason jar is made of glass that is microwave-safe. Any form of glass, even heat-safe glass, can be harmed by sudden temperature changes. It’s advisable to avoid using a Mason jar for reheating frozen meals, for instance. Food that has been frozen may leak cold liquid when heated, and glass may break due to instability issues brought on by the rapid temperature shift.
Because of this, it’s recommended to avoid using a microwave to thaw frozen food in a Mason jar. The Mason jar’s non-glass components are likewise not microwave-safe. Mason jars frequently include a metal lid or a ring around the glass’s rim to aid in sealing the lid. If you want to microwave your Mason jar, these components must be taken out.
How To Tell If Your Mason Jar Is Microwave-Safe
It is not always obvious whether or not a Mason jar is microwave-safe. The difference between heat-safe glass and normal glass is very subtle, and only professionals can determine the difference just by glancing at the glass. If you’re not sure whether your Mason jar is microwave-safe, here are a few indicators to look for.
Microwave-Safe Symbol
The microwave-safe symbol on the jar is the first thing you need to check for. Depending on the manufacturer, the symbol may have a somewhat different appearance, although it typically has a few wavy lines (indicating the microwaves). This sign is frequently printed inside the Mason jar lid or carved into the bottom of the jar.
The product information for the jar, which will typically state if the glass is microwave-safe, can also be found on the manufacturer’s website if you purchased the jar from them. You may also find information on the Mason jar’s labels if it was a part of a product’s packaging (such as a spaghetti sauce or candle jar). You may tell if the glass is not heat-safe by looking for the phrase “Not For Microwave Use” on some products.
The Jar’s Age
John Landis Mason patented Mason jars in 1958, and the initial versions were manufactured from normal glass to package canned foods, thus there was no need for the jars to be heat-safe. Manufacturers began employing heat-safe glass as the jars grew more popular for storing everything from canned meals to drinks and cakes, and even candles. If you have a new Mason jar, it is likely that the jar is composed of microwave-safe glass.
The Ball corporation manufactures the vast majority of Mason jars in use in the United States. If you see a Ball emblem on your jar, you can use this Ball jars infographic to determine its age. If the jar has a new Ball emblem on it, it’s probably microwave-safe.
Microwave Test
If all else fails, you can test the Mason jar glass’ microwave safety with a modest amount of heat. First, halfway fill your Mason jar with water, then microwave it for one minute on the highest heat setting. Check the glass in the Mason jar after it has been microwaved.
Your water should be appropriately heated, but the glass should be cool enough to touch without feeling uncomfortable. If so, you can microwave everything else without risk using the Mason jar.
The glass should not be used in the microwave if it is too hot. Your food and beverages might not be heated through correctly if you attempt to microwave it, and the glass might even crack or break after a few passes through the microwave.
How Long Can You Microwave a Mason Jar?
Even if you know you can microwave a Mason jar, the glass should be handled carefully to avoid cracking and breaking. Microwaving a Mason jar for an extended period of time may cause the glass to overheat, causing it to expand substantially and break when it cools.
That is why you should not microwave Mason jars for an extended period of time. Small Mason jars (30 fluid oz or less) can only withstand 2 minutes of repeated heating. Microwave medium-sized jars (30-100 fluid oz) for up to 5 minutes.
If you need to microwave something for a longer period of time, we recommend doing it in many bursts and mixing or stirring in between. This prevents the glass from being too hot from being microwaved for too long, and it also guarantees that your food is heated evenly.
Can You Freeze Food In Mason Jars?
Like heating, freezing is a challenge for Mason jars. If the temperature around the glass changes significantly, whether it is too hot or too cold, the glass will react poorly. Because of this, freezing food in Mason jars has the potential to break the jar if you aren’t careful. The first thing you should know is that while glass shrinks when placed in the freezer, water actually expands. In actuality, when water is frozen, it can grow by up to 9%.
Mason jars will compress as the liquid expands if you freeze any liquid in them because glass is rigid. The outcome? When the glass is taken out of the freezer, it won’t be able to withstand the pressure and will break. That implies that only solid foods should be frozen in Mason jars rather than liquids.
Mason jar contents shouldn’t be filled all the way to the top while freezing them. Filling the jar overly full will actually result in the contents spilling out when the jar shrinks since the jar will contract in the freezer. When freezing items in Mason jars, you should also avoid sealing the lid too tightly.
It will be more challenging to remove the lid once the jar is taken out of the freezer because the jar will shrink and the pressure inside the jar will rise if the lid is completely sealed. To prevent these problems, freeze the Mason jar for a few hours first, and then, when the jar is cool, secure the lid.
You should never use the microwave to defrost or reheat the contents of a Mason jar. Even though the glass is heat-safe, if the temperature transition from frozen to hot happens too quickly (for example, in the microwave), the glass will break easily.
Instead, you should leave the Mason jar to thaw out for a few hours at room temperature so that it does so gradually. After that, you can microwave it without risk. If you need to reheat your food quickly, you may also move the contents of the Mason jar to another container that can be microwaved.