Water Temperature
Water temperature controls which compounds leave the tea leaf and how fast, ranging from about 50°C for gyokuro to a full boil for black tea and pu'er.
Definition
Water temperature is the brewing variable that most changes a tea's character, not just its strength. Hot water extracts catechins and caffeine quickly, along with heavier aroma compounds. Cooler water favours sweet and savory amino acids such as L-theanine while holding back bitterness and astringency. Delicate, unoxidized teas are brewed cooler. Gyokuro is commonly brewed at 50-60°C (122-140°F) to bring out umami; sencha at 70-80°C (158-176°F); Chinese green teas at 75-85°C (167-185°F); white tea at 80-90°C (176-194°F). Oolongs take 90-100°C (194-212°F), with tightly rolled and roasted oolongs at the top of that range. Black tea, pu'er and hei cha are brewed at 95-100°C (203-212°F). Boiling point drops by roughly 1°C for every 300 m of altitude, so in a city such as Denver at about 1,600 m water boils near 95°C. That makes little difference to green tea but can leave black tea and pu'er slightly under-extracted. A variable-temperature kettle removes guesswork; without one, letting boiled water rest with the lid open, or pouring it between vessels, cools it in a predictable way.
In Depth
Cooling without a thermometer: each transfer of hot water between room-temperature ceramic vessels drops it by roughly 5-10°C. Japanese brewers use a yuzamashi (湯冷まし) cooling bowl for this reason, and pouring boiled water into cups first and then into the kyusu both cools the water and measures it.
Do not use reboiled or long-boiled water for delicate teas if fresh water is available; it tends to taste flat. Soft to moderately hard filtered water, low in chlorine, gives clearer flavor than very hard tap water, which can dull aroma and leave a film on black tea.
If green tea tastes bitter, lower the temperature by 5-10°C before shortening the steep. If an oolong or black tea tastes thin, raise it to a full boil before adding leaf.
See Also
- Tea Brewing Parameters
- Variable-Temperature Kettles
- Water for Tea