Microwave Water Boiling DANGER


I remember hearing that it was dangerous to boil water in the microwave when I was relatively young. Still, I was always a little skeptical because I heated water in the microwave to make things like hot chocolate or tea. However, the warning I got from my dad was valid! Please continue reading to see why it is typically safe to boil water in your microwave, what the actual danger is, and how to avoid it?

Answer: Due to superheating, boiling distilled water in the microwave is dangerous with explosive results; read below to find out why. However if you are boiling tap water, it should be safe to boil it in the microwave. It is also safe to boil other types of water, such as spring; however, as the water’s purity increases, one needs to be more aware of cook time.

Keep reading to see find out how to make water in the microwave safe!

This concept means if you are making a cup of instant coffee, it might be good to add instant coffee before boiling the water in the microwave. The same goes for tea and other things you might mix with boiling microwave water, such as noodles, a recipe pack, spices, or whatever people make that requires mixing with hot water.

I add salt packs to my nettie pot when I use it because I’m using distilled water which is purer, and I don’t want to heat it too high without realizing it.

If you are interested to learn more, keep reading about superheated water and watch this excellent video I found from Mythbusters on YouTube.

What are the Dangers With Boiling Water in Your Microwave?

I started this section really with one thing in mind, but there is another as well. First, we will look at superheating, and then we will look at unevenly distributed heat.

Superheating

Just like some villainous superpower, your microwave can make Superheated Water! As described on the FDA website is the real culprit here (click to read on FDA website, opens in new tab), but rather than regurgitate the FDA documents on this, check out this Mythbusters clip:

I describe this video below because I know how it is, and sometimes you don’t want to watch a video when you’re reading.

BOOM. Okay, maybe not that dramatic, but you can see the water did explode in the video. In the first shot, the experimenters, Jamie and Adam from Mythbusters, drop in a sugar cube into a superheated coffee cup of distilled water.

The key here is distilled as the distillation process removes all minerals and impurities from the water. So now, when the water reaches the boiling point, nothing happens. There is a similar phenomenon called super freezing, but that is a topic for another day.

But watching the cube drop into the cup, you can see the water spreads out around the cup and explodes up high. It may not be “high,” but it was high enough to hit the false hand approx 2-3 inches from the cup, maybe a smidge higher considering smaller bits of scalding water likely made it higher. I mean, the video quality is not that great, but it is a great example.

But the real show was the second explosion.

Mythbusters used a larger volume of water in a definite larger vessel, a Pyrex-style measuring cup. This time they drop a fork in it. Done! The explosive liquid goes everywhere! It was strong enough to blow the fork out of the measuring cup!

In a nutshell, when you have a clean container such as a coffee mug or measuring cup, you use immaculate water with no impurities. Your water can superheat. When this happens, the water is higher or much higher than the boiling point. Once this happens, it introduces impurities or the breaking of the surface tension on the top of the water, allowing it to explode out as it starts to boil instantaneously all over. Doing this, of course, shoots steam and gassed water everywhere. (I plan to do a video about this one, so make sure you sub to our YouTube channel).

This situation should be pretty easy to avoid. If you are careful each time you boil water in the microwave, you should be fine. It is expressed in the video when it is suggested to use distilled water.

However, our next one can cause you to burn your mouth. I know it has happened to me a few times.

Unevenly Distributed Heat

Have you ever reheated your pizza in the microwave? You know it is hot; you can feel the heat coming off the pizza as you bring it to your face. But you can’t wait, so you take a bite anyways, and the bottom bread is not too bad, so you take a full bite only to realize the cheese and sauce are at lava levels of heat.

This same thing can happen when you try to heat or boil water in the microwave. I only bring this one up because there have been times I know the water is hot enough to cook my ramen noodles and might even have a bubble or two.

It is a little ridiculous to think that someone would take the near-boiling or boiling water and take a drink, but I wanted to let you know about this potential other danger lurking in a coffee mug and microwave near you.

Really, for the most part, I think it is incredible the microwave sends the beams of heat out in a wave pattern and could create lines of heat in the water. Once the water starts to boil, it will mitigate the stratification effect of the waves to superheat some of the water locally.

The next thing you might be wondering about is the time it takes for water to reach boiling point. I’ve got you covered in the next section briefly and plan to make a resource page that will include a table that will consider the altitude, microwave wattage, and volume of water in both metric and imperial.

How Long to Boil Water in the Microwave?

To keep things simple, I’m adding a table here with wattage and estimated time. This chart is all for 1 cup. You should be able to double the time for 2 cups. When my page is completed, the information will account for altitude. I will link it here.

WattageSize (US)Time
6001 Cup4 min (un)
7001 Cup3 min (un)
9001 Cup2 min 10 sec
10001 Cup1 min 50 sec
11001 Cup1 min 15 sec
un = unconfirmed; this will vary based on your cup or container’s actual wattage, altitude, and even thickness.

How To Improve the Safety of Microwave Boiling

One way to improve the safety of boiling water in the microwave is not to use distilled water. If you must use distilled or any other water. Another way to increase safety is to add any ingredients such as salt, broth, sugar, or anything that will allow the microwave energy to distribute in the liquid and help mix it, allowing it to get that boiling action.

Another safety tip when boiling water in the microwave is not to be too hasty when pulling it out. If you have cooked the water long enough that it should be boiling and it is not, you should trust the fact that it could be superheated now, and you should approach with caution.

Spencer Heckathorn

Spencer loves to learn and try new things. He has been sharing his trials, successes, and failures, online since the early 2000s.

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