Water temperature, along with how much tea leaf we use, how long we steep it, and the quality of the water we use, is one of the only variables we have control over when brewing tea. It is often stressed in general tea information that one should use the right temperature for the right kind of tea.
But let’s look at water temperature in simple terms: entropy. More water temperature = more heat = more energy. More energy in the extraction solvent = more extraction from the tea.
When we consider the energy (heat) lost to the air, the teaware, the tea mass itself, temperatures can vary significantly between the inside of the kettle and the water once inside the brewing vessel. A starting temperature of 99C inside the kettle, will in a matter of seconds become 90C when actually brewing the tea. That is assuming the teaware is rigorously preheated, and the tea leaves themselves already wetted and hot from a rinse or previous infusion. Without such preheating, that 90C is more like 80C. And that is just a few seconds after the water has mixed with the tea. The temperature drops very quickly as more seconds go by, and heat radiates into the environment.
Simply put, more heat = more flavour. Not necessarily better flavour, but definitely more. If you use 100C kettle temperature, you will extract more from a given tea given the same conditions for everything else, than you would if you used 90C water.
Well, I hear you say, what about my Japanese green tea? You’ll burn them if you use 100C water! Well, you aren’t burning them. Remember, the same tea was exposed to above 100C temperatures during its processing.
Rather, a lot more stuff is getting pulled out of the tea than if you used 70C or whatever water. For green teas, that stuff tends to be more bitter, astringent, and pungent than for other tea types, due to the processing. So using cooler water, slows the rate of infusion of those (in this case) undesirable compounds, thus giving a more palatable infusion. But if you were to steep the tea for a longer time, in compensation for the temperature loss, you would likely end up with an infusion that tastes similar to one using hot water for a short amount of time. Given enough time, those undesirable compounds will indeed infuse into solution, regardless of the temperature. The higher temperature increases the rate of diffusion.
All of this is leading to me saying that I truly think temperature specificity for different tea types is overblown (ed: overblown, not purposeless). That is not to say that one should discount the use of different temperatures entirely, but I am asking you to consider what is actually happening when brewing the tea. If your purpose is the try and fully assess a given tea, you should use water that is as hot as you can possibly make it. This will get as much as you can possibly get out of the tea. For green tea, this might make the tea taste nasty if you brewed it the same way you did with cooler water. But try using quite a bit less leaves, and a much shorter time. Try setting aside preconceptions and tasting it for what it is, rather than writing it off as burnt because of the hot water. I dare say, you might be surprised by the results. There is more of everything.
There's enough inconsistency without constantly using different temperatures. The different teaware, that tea brewing session 2000masl, that middle of winter outdoor session where your tea gets cold super fast.
The other, perhaps more controversial reason, is that I think a lot of advice given about water temperature by people selling tea, either maliciously or not, is too cold. Steeping that oolong, puer, or black tea at 95C or 90C just serves to soften the tea up, not revealing all its true flavours, including perhaps flaws. Sure, tea brewed at 90C sure is soft and easy going. Steep it at 100C and all the uglies come out.
I’d rather spend my time drinking tea that can survive hot water and taste good, than messing about with different temperatures trying to make a tea taste good because it can't stand up to hot water.
This article may seem pedantic but that is entirely my point. I think getting pedantic over water temperature when making tea is a pointless distraction, which can sometimes distract you from the fact that the vendor says to brew at 88.567 degrees for 1 minute and 3 seconds just isn't that great.
Any discussion and criticism is more than welcome, we don't bite. Are you part of the boiling water master race? Or are you a martyr for the digital variable kettle war effort?
As always, remember to enjoy your tea.
You'll enjoy it even more with boiling water.
ADDENDUM: After some feedback, perhaps my intent was not clear enough with this article. The main purpose was to illustrate the relationship between temperature and extraction of tea. Of course, always using boiling water 100% of the time forever in every situation isn't going to be optimal for flavour, but in my opinion, one should err on the side of using boiling water, and adjust it only when desired results can't be achieved by manipulating other variables. I think for most teas out there, brewing at 90C or 95C simply means you are missing out on some of what that tea has to offer. Of course, if I wanted to be completely sanguine I would have simply said something like the best temperature for flavour is whatever you like best after experimentation, which is of course true, because taste is subjective.
Comments will be approved before showing up.