Heat is a selector. A leaf holds sweet amino acids, fragrant oils, and bitter tannins, each dissolving at its own pace — and the kettle sets the pace. Cooler water draws out the sweetness and leaves the harshness behind; boiling water opens every door at once. That’s why boiling water burns a delicate green into bitterness, while under-hot water leaves a black tea thin and flat. Same leaves, different instructions.

The map:

• Green — 70–80°C (Kenya Purple too)
• White — 80–85°C
• Oolong — 90–95°C; full boil for dark roasted styles
• Black, pu-erh, herbal & fruit — a proper rolling boil

No thermometer needed. Boil the kettle, leave the lid open, wait three to four minutes — that’s your 80°C. In a hurry, pour the water into your empty cups first: each pour sheds about 10°C, and it warms the cups too. Or let a variable-temperature kettle do the thinking — the one tea gadget that earns its counter space.