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I have a number of teas, some of which require a lower temperature for steeping than others (for instance, I have a particular Green Tea which asks for steeping at 70°C, 158°F).

I was wondering how to get the water to this temperature, and I can think of 4 different methods:

  1. Heat the water gently until it reaches that temperature
  2. Boil the water, then add cooler water until it reaches that temperature
  3. Boil the water, leave it standing for a couple of minutes until it reaches the temperature
  4. Boil the water, transfer it from vessel to vessel until the temperature drops sufficiently.

Is there any difference in the result of those methods, as to the quality of the tea it'll end up producing? Will it make a difference if the water (or some of it) never reached the boiling point?

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    Don't boil - heat to 70C then remove. If you're always using roughly the same amount of water in the same kettle you can measure it once and then do it by ear afterwards. 70C happens usually somewhere in the pre-boil rumble - there's a crecendo of rumbling that happens as the water heats which then becomes quiet before reaching full boil. physics.stackexchange.com/questions/28069/… – J... Aug 11 '16 at 20:32
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    @J... Please, if you want to answer the question, use the answer section. – Catija Aug 11 '16 at 20:38
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    @Catija If I did, I would. The information above is tangential and is not an answer to the question. The (brief) part that is an answer is already present in one of the existing answers below. – J... Aug 11 '16 at 22:34
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    Just for what it's worth: Electric kettles exist that can give you a range of "ideal" tea temperatures at the push of a button. Hard to beat a smart thermostat. – keshlam Aug 11 '16 at 23:36
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    There's even (expensive) tea makers that will let you choose the temperature and how long you want to brew and handle it by lifting the tea container after the desired time ( brevilleusa.com/the-tea-maker-onetouch.html ) – Thibault D. Aug 12 '16 at 12:38
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The method we use (for coffee) is pretty simple (though it requires some compatible equipment):

  • Fill kettle.
  • Shove probe thermometer through "whistle" hole in kettle spout.
  • Heat until desired temperature is reached.
  • Pour water into vessel.

If you don't have a kettle or your thermometer won't work, you can do the same thing with any pot and a thermometer that has a clip (so you don't have to hold it for 10 minutes while the water heats)... but be sure the thermometer is heat safe (candy thermometers are good for this if they have a high enough temp range).

You'll want to keep a couple of things in mind...

The temperature of your mug will cool the water when it makes contact. This is unlikely to make a huge difference but it's something to think about. If you really want to brew your tea at exactly 70 C, consider heating sufficient water to "warm" your cup (or teapot) by filling it part way and swishing the water around to heat up the cup first and then pour the water down the drain. Alternately, you can heat your water to a slightly higher temperature (72 C).

As to your other methods... I'm sure any of them would work just fine... they'd take longer, though, because you're waiting for something to boil and then you're waiting for it to cool off or you're futzing around with getting it back down to the "right" temperature by adding cool water or tossing it back and forth between cups.

Provided you have standard, municipal water that you're comfortable drinking from the tap (or filtered), I don't know why boiling it first would matter.

I'm also skeptical about the pickiness of tea being steeped at exactly 70 C. I have a feeling that there'd be little discernible difference (to the average consumer) were the water at 80 C or even 90 C... It'd be an interesting thing to test, I suppose.


As this relates to oxygen loss due to boiling, which has been mentioned in some of the answers. This related question actually discusses that already and the general consensus is that lower oxygen levels in the water is actually bad for the taste of the tea:

Dissolved oxygen is reactive, and will most likely extract more substances from the tea leaf, than without it. If these are the good flavour parts of tea, I do not know?

And:

This person found that increased oxygen in the water resulted in milder, less tannic tea.

So, it sounds as if not bringing your water to a full boil is actually preferable to the flavor of the tea (assuming you don't like the tannic flavors) because the oxygen is beneficial to the brewing process.

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    Boiling the water has not only the effect of killing any germs and, obviously, increasing the temperature, it also changes the chemical composition somewhat, in particular it purges much of the solved oxygen and CO₂. I do think this is relevant for the outcome of the tea – some people in fact swear it's essential that the water has boiled entirely and is only cooled afterwards. I'm not sure about this, somebody should do some blind tests... – leftaroundabout Aug 11 '16 at 18:30
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    @Catija I'm also skeptical about the pickiness of tea being steeped at exactly 70 C-- temperature can make a huge difference. If his tea calls for 70C and he uses 100C, its (most likely) going to come out bitter and disgusting. Anecdotally, I have done this myself-- green tea at too high a temp is not good drinking. – senschen Aug 12 '16 at 11:40
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For baking a rapid-bake loaf in my breadmaker a fairly precise temperature is required (enough to get the heat going quickly, not enough to kill it). This is easiest to obtain by mixing hotter-than-required water with cold water, stirring using a thermometer. If your cold water temperature is stable you can get really rather close by known proportions of boiling and cold. This may be good enough for you. But of course don't mix it over the tea (or yeast).

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    I'm lazy -- I run the hot water tap against the inside of my wrist 'til it's warm, then fill up my container, and it's in the 105°F to 115°F range. (this assumes you're in an area where the hot water tap is potable) – Joe Aug 11 '16 at 18:04
  • @Joe my hot water could be considered potable but I'm more impatient than lazy and the kitchen is a long pipe from the HW tank. – Chris H Aug 12 '16 at 5:54
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Boiling water reduces the amount of dissolve oxygen, and this will affect the taste of the tea. So boiling then cooling will result in different water than just heating to 70C.

Letting the water cool from 100C to 70C should keep the oxygen content low, but if you add fresh water, the oxygen content will rise again.

I don't think methods 3 or 4 will result in a taste difference, just a time to get there difference.

https://www.reddit.com/r/askscience/comments/12lz2q/about_boiling_away_oxygen_from_water_when_boiling/?st=irqnuldo&sh=c9af40eb

  • Yes... but how long do you have to boil the water for these effects to actually occur in any volume that is noticeable? The average user boils water until the kettle whistles and that's it. If you're suggesting this is the case, we're going to need info on how long the water needs to be boiled for any significant loss of gasses. – Catija Aug 11 '16 at 19:34
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    @Catija Oxygen is essentially insoluble in boiling water. And boiling is such a violent process that I think it takes what's left of the gasses out extremely quickly. My guess would be that, by the time you've decided the water really is boiling, the gasses are gone. – David Richerby Aug 11 '16 at 20:31
  • @DavidRicherby That's why I'm asking... I have no knowledge. All I could find is a graph on Physics.SE about how much oxygen is in water but it only goes up to 50 C... which, interestingly, it's already lost a lot of water (from room temp)... so it makes me wonder if the difference between the amount of oxygen in 70C water is really that great of a difference as what's in boiling water. – Catija Aug 11 '16 at 20:36
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    @Catija Googling for "oxygen solubility in water with temperature" gives solubility curves up to boiling, where it's essentially zero. It falls from around 9mg/L at 20C to around 4mg/L at 70C, which is quite significantly different from zero. – David Richerby Aug 11 '16 at 20:46
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The simplest way is to 1/3 fill the cup with cold water (from the tap/faucet), then fill with boiling water.

The water from the faucet isn't at exactly 0 degrees (being slightly warmer), but equally the water from the kettle isn't at exactly 100 degrees, so the two will balance each other to within a few degrees of 70c - close enough not to care.

It really is that simple. The difference in oxygen content will be negligible, as 70% of the water is still being boiled, and the other 30% is oxygenated by the act of pouring water into it.

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Boil and wait to cool is extra time and energy.

This is a trick I use with wine. I have old thick milk bottles I leave in the freezer. Then I just pour warm wine in the bottle.

However, pouring boiling water into untempered glass such as a milk bottle is likely to shatter it.

Use a thick metal vessel you leave in the fridge. Let water get to temp or higher. Pour into like a small cast iron tea pot at room temp or fridge temp. Hopefully it over-cools and just keep adding hot water until is gets up to temp. You could steep in the cast iron tea pot. It would also hold the temperature.

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On the comments on O₂ and CO₂ it is going to lose gas just heating. Gas is less soluble at high temp and solid is more soluble temp. It take very little time at that temp.

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I have a kettle (Breville) with buttons on it that heats water to different temperatures.

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