Kettle
The thing that heats the water, and therefore the piece of teaware that has the largest single effect on the cup. Temperature governs which compounds come out of the leaf and how fast, and a kettle that only knows boiling is a kettle that can only make one decision for you.
- Capacity
- 0.8 to 1.7 l
- Material
- stainless steel, glass or enamelled steel
- Origin
- universal
- Best for
- everything, and green tea specifically if it has a set point
What it is
A vessel plus a heat source, whether that is a stovetop kettle, an electric one, or a variable-temperature electric kettle with a set point. The variable-temperature kind is the meaningful category: it holds a chosen temperature instead of running to 100 degrees Celsius and stopping.
What it does to your tea
It decides the extraction. Heating 1 g of water by 1 degree Celsius takes about 4 joules, so bringing 250 ml from 20 degrees to boiling takes roughly 80 kJ, and the kettle itself takes a similar amount again: a 1400 g steel kettle needs about 60 kJ to come up with the water. That is why an already-warm kettle boils faster, and it is the same physics that makes a cold teapot steal heat from your brew.
What it suits
Everything, and the variable-temperature kind earns its price the moment you own a green tea. Sencha and gyokuro want water well under boiling, and getting there by guesswork is how a good tea turns bitter.
How to use one
Heat only what you need, which is both faster and less wasteful. If your kettle has no temperature control, the practical trick is transfer: pouring boiling water into a cold ceramic vessel drops it by roughly 10 degrees, so a route through a cooling vessel and a pot gets you into green tea range without a thermometer. If you live somewhere high, know your local boiling point once: water boils below 100 degrees as altitude rises, and nothing on the kettle tells you.
How to choose one
Variable temperature, a spout you can pour slowly and accurately from, and a capacity matched to how much you actually brew rather than to the largest number on the box. A gooseneck helps if you pour into small vessels. Stainless steel and glass are both inert; the interior is what matters, not the exterior.
Care and cleaning
Descale it. Limescale is the calcium carbonate that drops out of temporary hardness when you boil, and a furred element is slower and less accurate. Citric acid or vinegar, then two rinse boils. If your kettle has a filter at the spout, that is where scale flakes collect.
What people get wrong
Treating boiling as a single temperature and treating the kettle as a solved problem. Two kettles that both click off are not necessarily delivering the same water, and the difference between 80 and 100 degrees is the difference between a sweet gyokuro and a bitter one.
What it is made of
