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.
29 comments
Sharon
I used distilled water when we had a boil water notice. The tea was definitely lacking in flavor. Regretfully, when you work in an office, you have to deal with the microwave or Keurig machine provided, (unless I want to haul around my hot pot, and chance that someone else wouldn’t try to use it to make their soup), and tea bags. I have never found the scum in the microwaved cup that others have described, maybe that’s with a specific brand of bags.
I used distilled water when we had a boil water notice. The tea was definitely lacking in flavor. Regretfully, when you work in an office, you have to deal with the microwave or Keurig machine provided, (unless I want to haul around my hot pot, and chance that someone else wouldn’t try to use it to make their soup), and tea bags. I have never found the scum in the microwaved cup that others have described, maybe that’s with a specific brand of bags.
Josh
I have run some tests:
Boiled in kettle and poured into cup: 88.5 at the bottom, 90 at the top
Microwaved in glass container (rolling boil) and poured into cup: 92.9 at the bottom, 91.3 at the top
Microwaved in the cup: 100.4 at the bottom, 97.3 at the top
The takeaway here is that there is negligible difference if you boil it in a different container from the cup- the heat loss from transferring it to a not hot container is the biggest factor. But if you boil it in the cup that you then put a tea bag in, you might actually be cooking the tea, which could make it taste worse. Coffee is the same way – it should be brewed at 90-95 degrees.
I have run some tests:
Boiled in kettle and poured into cup: 88.5 at the bottom, 90 at the top
Microwaved in glass container (rolling boil) and poured into cup: 92.9 at the bottom, 91.3 at the top
Microwaved in the cup: 100.4 at the bottom, 97.3 at the top
The takeaway here is that there is negligible difference if you boil it in a different container from the cup- the heat loss from transferring it to a not hot container is the biggest factor. But if you boil it in the cup that you then put a tea bag in, you might actually be cooking the tea, which could make it taste worse. Coffee is the same way – it should be brewed at 90-95 degrees.
Delle
To the gentleman who stated he disagreed with everything in the article, your points are actually mistaken. Anyone who uses a microwave knows that food must be stirred as only the center heats. This center heating is known to cause very dangerous eruptions of hot liquid. Also, any kettle can be cleaned of deposits by occasional use of white vinegar which dissolved the minerals, so constant replacement is unnecessary. But, indeed, to each his own.
To the gentleman who stated he disagreed with everything in the article, your points are actually mistaken. Anyone who uses a microwave knows that food must be stirred as only the center heats. This center heating is known to cause very dangerous eruptions of hot liquid. Also, any kettle can be cleaned of deposits by occasional use of white vinegar which dissolved the minerals, so constant replacement is unnecessary. But, indeed, to each his own.
Mary B
Can anyone explain why heating reverse osmosis water in a glass mug in the microwave & adding green tea bag leaves mug full of scum by time I drink it all. this does not happen when water is heated on stove. mug remains clean.
Can anyone explain why heating reverse osmosis water in a glass mug in the microwave & adding green tea bag leaves mug full of scum by time I drink it all. this does not happen when water is heated on stove. mug remains clean.
W
You can get very specific temperatures with a microwave. Use a calibrated thermometer and learn the volume time combination and the simply stir the water. More accurate than a kettle and saves energy.
You can get very specific temperatures with a microwave. Use a calibrated thermometer and learn the volume time combination and the simply stir the water. More accurate than a kettle and saves energy.
Lynne
I’m surprised no one has commented on the SCUM! Whenever I have no alternative than a microwave, there is scum on my tea. I’ve never seen an explanation for that. Microwaved tea is almost not worth drinking…
I’m surprised no one has commented on the SCUM! Whenever I have no alternative than a microwave, there is scum on my tea. I’ve never seen an explanation for that. Microwaved tea is almost not worth drinking…
Michele
The British say NEVER use the microwave. They call tea bags “dust bags” as well. However, I’m American and sometimes pressed for time and energy so I’ll MICROWAVE!
The British say NEVER use the microwave. They call tea bags “dust bags” as well. However, I’m American and sometimes pressed for time and energy so I’ll MICROWAVE!
Sandra
Love your articles. Enjoy reading, always informative.
Love your articles. Enjoy reading, always informative.
Bill D
Been using mountain spring water for over 20 years in my kettles and no mineral buildup has occurred in all this time.
Been using mountain spring water for over 20 years in my kettles and no mineral buildup has occurred in all this time.
Rosslyn
Hi, I’m a tea snob. The best way (and safest way) to clean the mineral buildup from your tea kettle (stainless steel is best, in my opinion) is to pour in some plain white vinegar. Turn on the heat very low and swirl the kettle around a little. The minerals will dissolve in the vinegar. When its all dissolved just give the tea kettle a nice rinse and voila!!! . A sparkling clean, shiny kettle. Note: you DO clean your coffee pot with vinegar, don’t you? Same principal, but the method is just slightly different.
Hi, I’m a tea snob. The best way (and safest way) to clean the mineral buildup from your tea kettle (stainless steel is best, in my opinion) is to pour in some plain white vinegar. Turn on the heat very low and swirl the kettle around a little. The minerals will dissolve in the vinegar. When its all dissolved just give the tea kettle a nice rinse and voila!!! . A sparkling clean, shiny kettle. Note: you DO clean your coffee pot with vinegar, don’t you? Same principal, but the method is just slightly different.
Laura Wold
This was such an amazing article. I always tell people water from a kettle is better. I don’t even like the way my tea tastes if the water is heated in a microwave. I will be saving this for future use.
This was such an amazing article. I always tell people water from a kettle is better. I don’t even like the way my tea tastes if the water is heated in a microwave. I will be saving this for future use.
Lina B
Very interesting article, but the one thing that wasn’t mentioned is the taste difference. I drink mostly black tea and the taste is much, much better with water from the tea kettle.
Very interesting article, but the one thing that wasn’t mentioned is the taste difference. I drink mostly black tea and the taste is much, much better with water from the tea kettle.
Beth
What about using hot water passed through a Keurig? I take out the pod holder. It’s fast, no buildup, and I think the tea is great
What about using hot water passed through a Keurig? I take out the pod holder. It’s fast, no buildup, and I think the tea is great
Kathleen
My electric kettle gets mineral buildup from hard water. Covering the bottom with a little white vinegar for a few minutes while cold totally removes the buildup for me.
My electric kettle gets mineral buildup from hard water. Covering the bottom with a little white vinegar for a few minutes while cold totally removes the buildup for me.
John Stambaugh
Unless your water source is pure distilled water, there will be a build up in the kettle from contaminates in the water. Never saw a kettle that allowed for cleaning these deposits. So I say a constant replacement of your kettle is needed to maintain quality of your beverage. Your description oh how the water is heated by microwave makes me think the water is heated not just on the bottom but everywhere. Thus a more uniform heat. Also why microwave is faster than kettle. A microwave safe container is very easy to keep clean from water contaminates left from the heating process. I guess this all mean I totally disagree with everything you said. To each his own.
Unless your water source is pure distilled water, there will be a build up in the kettle from contaminates in the water. Never saw a kettle that allowed for cleaning these deposits. So I say a constant replacement of your kettle is needed to maintain quality of your beverage. Your description oh how the water is heated by microwave makes me think the water is heated not just on the bottom but everywhere. Thus a more uniform heat. Also why microwave is faster than kettle. A microwave safe container is very easy to keep clean from water contaminates left from the heating process. I guess this all mean I totally disagree with everything you said. To each his own.
Lorena
I agree that there is something warmer and more mindful using a kettle vs a microwave. At work, i use a microwave and I never feel the same sense of creating a break in the day as I do when I make tea at home. The microwave is more utilitarian and the kettle creates time to refresh.
I agree that there is something warmer and more mindful using a kettle vs a microwave. At work, i use a microwave and I never feel the same sense of creating a break in the day as I do when I make tea at home. The microwave is more utilitarian and the kettle creates time to refresh.
Judy Plourde
My mother would roll over in her grave if I ever used the microwave. Always the kettle! She judged restaurants by how they served her tea. Had to be in a pot to earn her approval. Also even at a picnic we had a mug for her. Never a paper cup! That’s how I was brought up.
My mother would roll over in her grave if I ever used the microwave. Always the kettle! She judged restaurants by how they served her tea. Had to be in a pot to earn her approval. Also even at a picnic we had a mug for her. Never a paper cup! That’s how I was brought up.
Julie S
The graphic appears to be incorrect, but I get the idea. Also, if all warmer, lighter molecules go up, and all cooler, heavier molecules go down, it seems to imply that the microwave heats only at the top (and, thus, the warmer molecules stay on the top and the cooler ones stay in the bottom) YET the microwave description is ( accurately, I believe) that the microwaves bombard the water from all sides, thus eliminating the need for the circular mixing, yet heating all portions more or less equally. Well, I could be prejudiced because I’m a microwave girl!
The graphic appears to be incorrect, but I get the idea. Also, if all warmer, lighter molecules go up, and all cooler, heavier molecules go down, it seems to imply that the microwave heats only at the top (and, thus, the warmer molecules stay on the top and the cooler ones stay in the bottom) YET the microwave description is ( accurately, I believe) that the microwaves bombard the water from all sides, thus eliminating the need for the circular mixing, yet heating all portions more or less equally. Well, I could be prejudiced because I’m a microwave girl!
Camille
It must be a cultural thing, in France everybody I know use an electric kettle (bouilloire in French), I never tried to microwave it
It must be a cultural thing, in France everybody I know use an electric kettle (bouilloire in French), I never tried to microwave it
Diane Knoble
I would also ask about mineral buildup in the kettle. Is there a way to prevent it from happening or at least lessen it?
I would also ask about mineral buildup in the kettle. Is there a way to prevent it from happening or at least lessen it?
Mary
But which method has the lighter carbon footprint? Surely that matters too….
But which method has the lighter carbon footprint? Surely that matters too….
Katherine Steiger
What’s the best way to clean the kettle to ward off mineral build up mentioned above?
What’s the best way to clean the kettle to ward off mineral build up mentioned above?
Debbie S.
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.
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
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.
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
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!
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
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.
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
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.
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
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.
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
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
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