06 June, 2009

Temperature vs. Induction

I've recently had an e-mail asking for a "tetsubin reloaded" article to follow my previous tetsubin article - thanks for the letter, Dr. Kim! It's been on my mind, but I've not got around to taking a photograph of my hot-plate. Let me remedy that immediately:

My hot-plate: it is hot, and it is like unto a plate

Regular readers may remember that Lei and I switched from our previous kettle (the popular Kamjove induction system) to the above set-up. In a previous article on the heating-via-induction process, I mentioned that we made the change because the inductor was (i) noisy, due to its fan; (ii) irritatingly "beepy" due to the electronic noises it makes in response to every pressed button; and (iii) subjectively discomforting due to the presence of a high-frequency induction coil. Maybe you don't find the latter to be a problem.


The induction system certainly has its advantages: it is extremely efficient at heating water, and so there's very little waiting for water to boil. However, I usually only sit down to a proper gongfucha session if I am deliberately trying to slow down, and have an hour or two to spare. These days, that means Saturday morning, or Sunday before heading out to chapel, unless I sneakily grab a session before heading into work. So, quick boiling isn't a very high priority for me.

In fact, you know, the gradual process of the tetsubin is actively positive. It slows me down. It slows. Me. Down.

I like being forced to be slow. It empties out all the nonsense from my head, usually filled with half-formed plans and concerns. Papers. Chapters. Projects. Students. Positions. Using the hot-plate pictured above, the tetsubin takes about two or three times as long to boil water as does the inductor. And I like that very much. Doesn't that sound pointless? However, it doesn't work like that. There's something tangible and real about the tetsubin. Its slowness has turned out, unexpectedly, to be a positive boon.

What do I do while waiting for it to boil? Nothing. I do nothing, or at least I try to do nothing. And, as every practioner of zazen will tell you, that's a very hard thing to do. The results I find to be highly beneficial.

Sofa and Book
A typical view from the tea-table

Everyone's Got to Have a System

I've got used to our dear tetsubin in the last four months, such that it is now an unconscious part of my routine. I have learned its sounds to help my understand the temperature of the water, and have reached a good state in making tea intuitively. As always, the process of improvement is a constantly ongoing one.

I'd like to describe some points that I've come to find useful in using my tetsubin. Of course, this is (as always) what "works for me". My eternal advice: think about it for yourself.

(i) I don't like boiling the same water over and over again, and I don't like keeping one large batch of water on the boil for ages. This is my preference; I know some people like to keep it "rolling" using a small tea-light. There's no right answer, but this is my way. To that end, I don't heat up a big batch of water: I heat up enough water for two pot-fulls. This comes to about a third of the tetsubin capacity for my equipment. (Be careful not to boil a tetsubin with too little water, or you will crack it.)

(ii) After filling the pot, this leaves me without enough water remaining in the tetsubin for another pot. I put the tetsubin on our iron trivet (the round, white object to the left of the hot-plate in the above photograph), and remove its lid. The kettle and the water inside begin to cool, and I turn my concentration to the infusion taking place in the pot. While I mess around brewing the tea, the kettle and its water continue to cool on the trivet.

(iii) When it comes to the next infusion, I have a warm tetsubin containing warm water. This water remaining in the tetsubin acts as a temperature buffer, allowing me to add (room-temperature) water for the next infusion. I add the new water slowly, and it mixes with the warm water so as not to cause too large a temperature differential in the iron of the tetsubin. Iron doesn't like significant temperature differentials. (The Japanese tea ceremony takes this to its extreme by cooling a used chanoyu kettle gradually, by pouring warm water over its exterior, until it gradually approaches room temperature.)

(iv) Now, I have 50% new water in the pot, and only 50% from the previous infusion. Over time, it is reasonable to assume that this remaining fraction of water in the pot decreases by half each time, so that the water is never too old, nor kept hot for too long. That works for me.

Red Rose

The Taste

I read an article some time ago on a vendor's web-page that said tetsubins were unsuitable for shengpu. I know several teachums who were actively dissuaded from buying a tetsubin by this article. It's very dangerous for people to write such statements - particularly without providing any explanation, as did this article. Zen Buddhists have a tradition of avoiding definitive statements for this very reason: it is dangerous to say something that could mislead a listener, and it may be better to say nothing at all.

To offer contrary evidence to the article, I have found the water from a tetsubin to be highly complementary to shengpu, both young and old. These are not definitive statements: I urge you to understand that these are my opinions, and at best relate to the water I use (bottled spring water), to the tea that I drink, and to my method of brewing. I have found the results to be pleasant, and I suggest that you come to your own conclusions, if possible, by trying out a tetsubin for yourself, if the opportunity arises.

To my reckoning, the water is smoother than that obtained from our induction system. It is "rounded", gradual, and more mineral, when consumed plain. When used to brew tea, I have found its mineral character to emphasise shining high-notes that I previously did not detect, and to amplify the effect of the huigan [swelling return-sweet character in the throat].

In engineering terms, it amplifies "higher frequencies" in the character, such as the ringing high notes, the aroma, and the huigan, and it attenuates roughness. My plantation teas taste much more palatable with tetsubin water, for example. Bass notes, such as leather, tobacco-like undertones, seem largely unaffected - if not a little more smooth.

There is a difference, and you may not like that difference - so try it, and see for yourself. I like the difference, and I would not recommend the "unsuitable for shengpu" statement for the general audience.


It is very important to dry your kettle after use. Happily, this is very easy: when the hot-plate is finished after use, just leave the empty tetsubin on it for a half-minute, and the residual heat will evaporate the thin film of water remaining on the interior of the kettle. Don't leave it sitting too long, as heating without water (even on the cooling-down heat of the used hot-plate) will not be beneficial taken to the extreme.

One thing I learned was that it is very easy to leave water in the tetsubin and forget it! I habitually used to neglect my induction kettle in this way, and come back to the tea-table the next day to find that I had left water in it. No problem, the induction kettle was protected from oxidation. The tetsubin, however, is not so well protected, and needs careful attention. Don't run off and leave your kettle with water in it!


Nerval said...

A very useful artice, thank you.
I am contemplating buying a tetsubin and your impressions are really valuable. While I did not read the tetsubin vs. shengpu article you refer to, the influence of the kettle on the taste of tea is a crucial question.
One thing left me wondering. I remember reading that in orthodox gongfucha, you musn't mix boiled and unboiled waters, as their 'qi' do not agree. You are expected to heat new water from scratch for each subsequent infusion (if boiling water is needed at each time).
I wonder whether the taste of such waters is notably different.
Best, Nerval

Hobbes said...

Dear Nerval,

Thanks for the comment!

The "fresh, hot water for every brew" maxim is tackled by each of us in his own way. My own approach, which I hope came out in the article, is to retain a little from the previous infusion as a temperature buffer to protect the tetsubin. I began by boiling entirely new water each infusion, but without a buffer, the differential in temperature is discomforting.

The notion of reading about "orthodox gongfucha" is interesting, as it is an organic practice. Be careful to whom you invest your notions of authority. :)



Kim said...

Thanks a million, Hobbes !!

Hobbes said...

Tip o' the hat :)

speakfreely said...

Nice. I was interested in your opinion of whether or not what the vendor said about tetsubins and shengpu was so, and here is a careful and well-considered post on the topic! As always, you rock.

Hobbes said...

Thank'ee ma'am - can you remember which vendor it was? It was one of the tetsubin sellers!

The article itself was very good, and written to inform, in good faith - but that clause put quite a few folk off good kettles.



ginkgo said...

I have the same systhem in my workshop : an electric owen and a iron tetsubin, an old one . It has changes the taste of my teas and I use just current water because it comes from the mountains narrow.I notice teas are more sweet and that the deep notes are put in front. With pu er it is marvellous tastes but with green teas, specially the delicate one , the water is a little bit too heavy, I think. I hope you can understand me because it is difficult to write in english...and find the exact words... I aggree with the slow time .. I have to wait too, until the water is ready but the tetsubin is large and so I have enough water for the entire afternoon, my iron owen can keep the middle temperature right... That is fine !

Will said...

I have seen different schools of thought about replenishing the water every time -- and with a traditional Chaozhou clay kettle, it seems unlikely that you would want to empty it completely and pour in fresh cold water, due to the risk of cracking. I generally do the same thing as you do (add fresh water to the hot water as necessary). I think to use up the water completely without adding water or reboiling (or close to completely), you need a really small kettle (like the ones used for traditional Chaozhou gong fu). Those kettles are small enough that you really can't use them for more than 1 or 2 brews, even when using a really small pot.

However, one piece of conventional wisdom that I have *not* heard debated much is that water should come to a boil quickly. Almost everything I've read or heard claims that makes a difference. Personally, I can't taste the difference, but while I am not a slave to tradition, I also don't believe that just because I can't taste a difference, one doesn't exist.

I currently use a hot plate myself, and with a glass kettle, it's probably even slower than a tetsubin -- about 15-20 minutes to bring less than 1 liter to a boil. Recently, I've been pre-heating it on the stovetop for the first brew, which gets things started a little quicker (about 6 minutes).

Preheating the water in another brewing vessel is one approach that lots of people (and shops) I know of use. I wonder if this affects the water quality.

Hobbes said...

Dear Gingko,

Thanks for the comment - very clear, fear not! You made me realise that I have not brewed lucha "properly" for a long time - if I do have any, it is brewed with little attention in my office. I have got used to not having lucha around, simply because of its limited shelf-life. I think I should buy some more, in small amounts, and have some fun with it at home.

Dear Will,

You raise a very interesting point. Intuitively speaking (i.e., with absolutely no basis on which to rest, rather just an opinion) it would not seem ideal to bring a very large amount of water gradually to the boil. I like to have just enough for two infusions in the kettle, which takes perhaps 5 mins or less to reach a boil. Taking 15-20 mins would make me a little uncomfortable, I think - but that's just my intuitive feeling. I know many people boil the same water over and over again and have no problem, so there is room for plenty of experimentation and differing approaches.

Whether or not there is a real difference (and confirmation bias tells me that there is!), I like to avoid: (i) reheating old water, within the limits of keeping a small buffer to avoid cracking, and (ii) not taking a huge amount of time to heat it.

I haven't tried heating the tetsubin over a flame, partially because of some articles and experiences that I read describing undesirable consequences for the skin of the kettle. However, I can't see other temperature-based methods (i.e., not induction) resulting in a great decrease in boiling time - there is only so much heat that can be transferred from source to water via the medium of the kettle's metalic lattice!

For that reason, I wouldn't like to preheat, either - the idea of keeping old water hot for a long time doesn't feel too comfortable. (Opinion, again.)

Interesting stuff!



Matt said...


One wanted to wade into this topic during your post on induction heating, but due to being in transit at that time, was unable to do so.

Firstly, due to Korea's rush-rush, modern attitude, one saw many induction kettles in use by various prominent tea people and shop owners. Often the kettles contained metal magnet stones or some kind of silver beads inside them. The masters were aware that this type of heating negatively impacted the qi of the water so they put these these inside to 'stabilize the qi' and/or 'minimize the loss of qi' in their water. Stephane from teamasters has an interesting article ( http://teamasters.blogspot.com/2005/10/chinese-water-is-best-for-chinese-tea.html ) about how activated bamboo charcoal can add qi to water when placed inside a tetsubin, something one is playing around with these days.

Could you comment on the science of such devices in regard to minimizing the invasiveness of induction heating?

One hoped to have an upcoming article about the art of using a charcoal brazier and clay tang gwan (tetsubin) and how it impacts the water used. But seeing as ones ceramic tang gwan didn't survive the journey to Canada perhaps it will have to wait until a new one comes (guess who's using the induction heated kettle with charcoal now?).

The Korean style tetsubins (tang gwan) are made of clay, but the method you described of adding water as you go is a common method used by all masters in Korea (the ones who don't use the induction heaters of course).

Will is right, there is much said about how fast water comes to a boil can affect its qi. In ones experience, it is not so much how fast your water comes to boil that affects its qi, but the stage of boiling that the water is in when used that impacts the interaction of water and tea. This is epically true when using charcoal heat.

And you think your set up is slow ;)


Hobbes said...

Dear Matt,

You are one of the most well-travelled people I know!

I have only toyed with the charcoal that you mentioned (I have some from Stephane Erler), and found that it did have a pleasing effect - but it was a little too pronounced for my taste. There are additives, and then there are additives!

As regards to the science of such devices - I couldn't comment, as a scientist, because I have no information on which to base an argument. If you grant me wild supposition, then I wonder if the addition of minerals via charcoal is compensating for some perceived lack of something else that may come about via induction. From my experience, I didn't find induction heating to change the taste of the water. Rather, the material of the kettle seems far more significant a variable.

I'm looking forward to reading your article on charcoal heating, as I have personal benefit in mind! I believe that I have successfully convinced Lei that we need a small folly/pagoda/wooden construction in our new garden, once we've redesigned it, in which to drink tea. Then, charcoal heating will definitely be on the cards!

I do love the aural effect of heating by charcoal. Plink, plonk, plink... wonderful stuff. There are Chinese poems about just that.

Toodlepip, and best wishes,


speakfreely said...

Hi there. Yes, the vendor in question seems to have a personal relationship with several tetsubin manufacturers, and has a great informative website. Which is why I wondered seriously about their recommendation, which can be seen here:


Hobbes said...


miig said...

Dear Hobbes,
its a bit late for a comment, but I think that this question fits well here:
I've been using clay kettles until now and would like to venture into the realm of iron kettles now.
These clay pots are nice and beautiful, but much more fragile than even a tetsubin, it will take 20mins to heat water in those, too. But they cool down very fast, so its easy to use fresh water each time.

Now the question: If i were to use the same approach with iron kettle, how long would it take for your tetsubin to cool down enough that you could pour water in it without shocking the material?


Hobbes said...

Dear Miig,

A great question! I tend not to be precious about my tetsubin, and simply introduce more water as needed (but never into an empty, hot tetsubin - I keep water in the tetsubin between brews to act as a temperature buffer). Tetsubin seem to be strong enough. :)