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Can You Put a Thermos in the Microwave? (Read This First!)

Thermos is increasingly gaining popularity among people for the convenience that they offer. But can you put a thermos in the microwave? How much temperature can thermos withstand?

Today we will discuss these important questions to help you learn more about the functions of the thermos. Read ahead to find out.

Can you put a thermos in the microwave?

You can put thermos in a microwave without any trouble. It offers great convenience in being able to use a thermos directly in the microwave. But you will have to be careful. Thermos may not heat up food inside as evenly as a glass appliance. And make sure to not put the lid on the thermos.

You can put a thermos in the microwave without facing any real problem. A thermos can generally withstand the temperature that is needed to reheat or heat up food. But you should be careful while putting a thermos inside the microwave.

While thermos offers incredible convenience, they are not able to heat up food in the microwave as well as plastic or glass pots. Thermos will not be able to heat up the food as evenly or thoroughly. However, it will get the job done.

In addition, you will have to ensure that the lid is open when you put a thermos inside the microwave. Otherwise, the food will not be heated.

Be alert when you put a thermos inside the microwave. Watch out for sparks of any sort as your thermos may catch some sparks here and there when it is put into the microwave. In such a case, stop the microwave immediately and bring out the thermos.

Thermos flask:

You can safely put a thermos flask inside the oven. But keep in mind that it cannot withstand very high temperatures. It is okay to put a thermos flask inside the oven as long as the temperature is kept in control.

Plastic thermos:

Many thermoses include plastic components inside. Even these plastic thermos can be put inside the microwave.

But in the case of a plastic thermos, make sure that it is not kept inside for too long. The plastic thermos may release chemicals into the food if it is kept inside the microwave for long.

Stainless steel thermos:

Stainless steel thermos can be put in the microwave. But we do not recommend it. The metal in the stainless steel thermos will reflect the microwave rays and make the heating process very inefficient.

It will take much longer for the stainless steel thermos to heat up. That said, the stainless steel thermos can withstand heat for much longer than any other material.

Be careful when you’re bringing out the stainless steel thermos from the oven as its exterior gets very hot. Use oven mitts when working with stainless steel thermos.

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Will putting a thermos in the microwave break my thermos or microwave?

Putting a thermos in the microwave will not break your thermos or the microwave. However, if you’re not careful, then your thermos may sustain some cracks on the internal layers.

Thermoses are made of several layers of materials. These layers are designed to trap heat inside the thermos. Some of the internal layers are made of glass or plastic.

If your thermos is old, then it is likely that those layers may have some microcracks in them. If you heat up a thermos that is in bad condition, then it may sustain some large cracks. The layers inside the thermos may even break sometimes.

So you should always be careful when putting your thermos inside the microwave. They may sometimes catch sparks as well. If you don’t pay attention, then the thermos may blow-up inside. So always keep an eye on your thermos after putting it in the microwave.

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What happens if you put a thermos in the microwave?

If you put the thermos in the microwave, it will heat up the food inside. But the process of heating up food in a thermos using a microwave is often deemed inefficient. Because it takes much longer than any other container that you would use.

Most thermoses are made using several layers of materials. This is done to contain the heat inside the pot, and prevent it from losing temperature quickly. This is what makes putting a thermos inside the microwave inefficient.

Since there are so many layers inside the thermos, it takes too long for it to heat up inside a microwave. Penetrating all those layers takes longer than containers that are made of plastic, ceramic, or glass.

But if you have to use a thermos, make sure to preheat it before putting the food inside the thermos. Use boiling water to heat up the thermos before putting it inside the microwave. This will make the heating process much efficient.

2 reasons why thermos is microwave safe

Thermos is oven safe. Here are some of the most prominent reasons why thermos is considered microwave safe:

Several layers of material:

Thermoses are generally designed to be very strong units. There are several layers of materials surrounding the inner bowl. Typically, materials like glass and plastic are used inside a thermos.

These materials are microwave safe. This makes thermos microwave safe as well.

It can heat up and trap the heat inside:

Another incredible function of the thermos is that it can trap heat inside the unit for a long time. You can heat up food in a thermos, but you will need to make sure that the lid is removed.

Once the food is heated, closes the lid and the thermos will be able to keep the food heat for a long time. This makes thermoses microwave safe.

How do you heat up a thermos?

Heating up a thermos is quite a straightforward process. It will get even easier if you follow these steps to heating up a thermos:

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Boiling some water:

The first step to heating up a thermos is to boil some water separately. Then fill up the thermos with the boiling water. Close the lid of the thermos and wait for about 10 minutes.

This step is done so that the thermos is preheated easily. If you try to heat up food in a cold thermos in the microwave, the process will take much longer than you’d like.

Put food inside the thermos:

Now take out the boiling water and wipe it, allowing it to dry. Then put food content inside the thermos.

Put the thermos in the microwave:

Now put the thermos in the microwave with food in it. Remember to remove the lid from the microwave at this point. Microwaving with the lid on will block the heat from reaching the food, taking much longer to heat up.

Once you have your food heated, take the thermos out of the microwave. Remember to use oven mitts, thermos may be too hot for your bare hands. Quickly put the lid on the thermos and pack it up to prevent heat from leaving the unit.

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Do you need to preheat a thermos?

Yes, you will need to preheat a thermos in order to heat up food inside. It is essential that you follow a preheating process before putting the filling inside the thermos.

This process will make heating in a thermos much more quicker and efficient. It will allow your food to remain warmer for longer as well.

How long does it take to heat up a thermos?

Thermoses generally take longer to heat up in comparison to glass or plastic materials. So you will have to wait longer to heat up your food in a thermometer.

On average, it takes between one to three minutes to heat up a thermos.

Keep in mind that thermoses need to be preheated. You will need to preheat the thermos before you put in any food or other fillings inside the thermos. This will make the heating process much more efficient.

How long does a thermos keep food hot?

How long a thermos keeps food hot largely depends on the type of thermos that we are talking about and its material. But in general, a thermos can keep food hot for up to 5 hours.

A premium quality thermos can keep food hot for even longer, sometimes even as long as 12 to 24 hours.

However, there are many low-quality thermoses in the market that will be unable to keep food hot for even a couple of hours. So the duration mainly depends on which product you are using.

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Final Thoughts

You can put thermos in a microwave. But heating food in a thermos is considered inefficient as it takes much longer than glass, ceramic, or plastic. So consider not putting your thermos in the microwave unless you have to. In that case, preheat the thermos to get the best heating results.