by Emeric Harney September 10, 2020 3 min read 8 Comments

Heating water for your tea. Whether you heat the water in a kettle on your stove or in a mug in your microwave, you still get the same thing: hot water. Well, technically that’s correct. But science tells us there’s a difference. And, if you pay close attention, your tea will probably tell you the same thing.

It may not be an epic showdown like Batman vs. Superman or the Jonas Brothers vs. One Direction, but when you pit a kettle vs. a microwave, you might be surprised who wins.

Science. It’s a Thing.

Because the ways a kettle and a microwave heat water are very different, so are your results. Let’s let science tell us how and why.

Kettle. Water heated in a kettle is heated by convection. Here’s how convection works:

  • Convection is the circular motion that happens when warmer liquid—which has faster moving molecules, making it less dense—rises, while cooler liquid drops down.
  • When you turn the kettle on, heat is coming from the bottom, not bombarding the liquid from all around. As the water on the bottom heats first, it rises (see “convection” above for why), while the cooler water begins to drop down.
  • When this happens, eventually the water mixes together to create a uniform temperature. It’s like starting out with a bowl of ice cream, with chocolate on one side and vanilla on the other. If you mix them together, you get chocilla, or vanolate. That is not science, but you get the idea.

Microwave. Basically, a microwave works like this:

  • Inside your microwave’s metal box is a magnetron, an electron tube for amplifying or generating microwaves.
  • Microwaves are electromagnetic waves with a wavelength that is shorter than that of a radio wave but longer than infrared radiation.
  • When you hit the start button, the magnetron converts electricity flowing from your power outlet and converts it into microwaves, which are blasted into the box through a channel called a wave guide and bounce off the interior metal walls.
  • When the waves hit your food, or water in this case, they don’t bounce off. Instead, they pass right through your water.
  • This gets the water very excited, and its molecules begin to vibrate. Their vibrations have heat, so the faster the molecules vibrate, the hotter the food becomes.
  • However, because these electromagnetic waves are coming from all over the microwave (imagine a dog chasing more than one squirrel) instead of just from the bottom like a kettle, convection (the mixing of heat) doesn’t happen.
  • The result? The water at the top is hotter than the water at the bottom. This does not make for a consistent, best-of-class tea-drinking experience.

So, there you have it. Heating water for your tea in a kettle will give you water that has a uniform temperature. Since we recommend that you prepare your tea at specific water temperatures based on the type of tea, heating water in a kettle is the only way to do that. A microwave will give you water that is hot, but the temperature is not consistent throughout the cup.

Also, if you have ever tried to take a microwave on a camping trip, you know that a kettle is the much better choice.

Got Kettle?

Hopefully you’ve already got a beloved kettle at home, the first thing you reach for as you stumble into the kitchen in the morning to make your English Breakfast tea, and the last thing you use in the kitchen as you make a cup of Deep Sleep tea before bed. Whether your kettle is new and shiny or old and well-used, make sure you clean it periodically to keep it free from mineral build-up, which will diminish the taste of your water. Always use cold filtered water so the flavor of your tea comes shining through.

If you’d like a kettle that makes sure your water is the perfect uniform temp every time, try the Cuisinart Perfectemp® Stainless Steel Cordless Programmable Electric Kettle. With six preset temperatures, a keep-warm option and a water filter, you’ll have perfect water every time. Need tea on the go and don’t want to pack that microwave? The Bonavita Mini Electric Travel Kettle is your tea-lovin’ travel buddy and provides quick, even heating. All you need is water and an outlet. Oh, and tea and a mug.

At the end of the day, while we all love the convenience of microwaves, the kettle is the clear winner in the water-heating battle. Plus, there’s something very lovely and quasi-British about saying to a friend before you settle in for tea and a chat, “Let me put the kettle on”… “Let me start the microwave” just doesn’t have the same feel.

Emeric Harney
Emeric Harney


8 Responses

Katherine Steiger
Katherine Steiger

September 17, 2020

What’s the best way to clean the kettle to ward off mineral build up mentioned above?

Debbie S.
Debbie S.

September 13, 2020

I cannot imagine making tea in a microwave, ever! I love my tea kettle and could not be without one as I use it several times during the day and evening.

Juliebeth
Juliebeth

September 13, 2020

I totally agree! The Tea taste is so much better from boiling the water than heating in a microwave. What I’ve also noticed is the tea stays warm longer from boiling the water than heating in a microwave. So if I’m staying at family or friends houses that don’t have a kettle I heat my water in a pot, a little tricky pouring it in my cup but just can’t use the microwave.

Kris Hopper
Kris Hopper

September 13, 2020

What you say makes sense. But if one does use the microwave, one can stir the water til all the water is uniformly heated. Kind of like when one heats up baby’s milk; after it is in the mic, one has to shake the bottle to evenly distribute the heat.
But I agree with you, “let me put the kettle on!” sounds so much more friendlier and cozier. The process in putting the water on and heating it via “the fire”, gives one a sense of accomplishment when the tea is brewed the “ole fashion” way!
Great way of explaining the heating process between the two ways. Thanks!

Valerie Lull
Valerie Lull

September 13, 2020

I remember putting the kettle on a wood burning stove. It tasted wonderful. I think it was because it was all such a cozy experience.

Valerie Lull
Valerie Lull

September 13, 2020

I remember putting the kettle on a wood burning stove. It tasted wonderful. I think it was because it was all such a cozy experience.

Robert Randall
Robert Randall

September 13, 2020

Nice piece, but I think that it may go deeper than that. Boiling in a kettle precipitates some minerals (calcium mostly in our ketle) and I think also boils off some dissolved gasses (oxygen and carbon dioxide among others) leaving the hot water chemically different in some ways. Don’t take my word for it. Ask someone who majored in chemistry and thermodynamics. I’m neither.

Donna V
Donna V

September 13, 2020

I miss your dad ~ everyday I drink a cup of “PARIS”. The articles are so timely and I love HARNEY & Son Teas.
I used to own our own teashop in Dallas TX but my husband was diagnosed with ALS (Lou Geghris) and we closed the shop… then he passed BUT I still talk tea everyday.
Keep up the GREAT WORK you all are doing! Mr. Harney would be soooo very proud of you all… even during the pandemic “Still Thriving” ~ dV

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