Living Water: The Secret to Unlocking Boseong Teas
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Living Water: The Secret to Unlocking Boseong Teas
"Water is the mother of tea." In Korea, this ancient truth guides every preparation. A complete guide to ideal water, temperature, minerality, and mistakes to avoid.
By Maison Boseong · Seoul, South Korea · June 2026 · 6 min read
It is often said in Korea that "water is the mother of tea". You may own the most prestigious Boseong Woojeon: if the water is not chosen and treated with care, the heart of the leaf will remain dormant. Water is not just a vector. It is an ingredient in its own right.
Minerality: The Enemy of Umami
Korean green tea is famous for its delicate sweetness and umami flavor. These qualities are directly threatened by water that is too rich in minerals. Here's why.
Calcium and magnesium present in "hard" (calcareous) waters bind to the polyphenols and amino acids of the tea from the first seconds of infusion. These bonds prevent aromatic compounds from being properly released into the water. The result: a "flat" tea, which loses its sweetness and length on the palate. In extreme cases, an oily film forms on the surface of the cup: this is the precipitation of oxidized calcareous compounds.
The golden rule: choose water with a dry residue of less than 100 mg/L (ideally 50 mg/L or less). Very soft water allows the tea's aromas to express themselves freely.
Temperature: The Most Important Parameter
Water temperature is the parameter that most directly impacts the taste of Korean tea. Water that is too hot is the primary cause of bitterness in green teas. Here are the ideal temperatures according to grade:
Ujeon
The most delicate grade. Above 68°C, umami compounds degrade.
Sejak
The ideal range for daily Korean green tea. Never use boiling water.
Joongjak
The more robust grade tolerates slightly hotter water.
Hwangcha
Slightly oxidized leaves require a little more heat.
Hongcha
Korean black teas can withstand almost boiling water.
Matcha
For whisked Korean matcha. Above this, the foam forms less well.
« Taming water is showing humility towards the leaf. It is the first step to bringing all the purity of Boseong into your home. »
Oxygen: Never Boil Twice
A very common mistake: boiling water, waiting for it to cool, then re-boiling it. This seemingly innocuous gesture profoundly degrades the quality of water for tea.
Fresh water contains dissolved oxygen. When boiling, this oxygen escapes. If water that has already been boiled is re-boiled, it loses even more oxygen. However, it is precisely this dissolved oxygen that allows the tea's aromas to "jump" out of the leaf and be released into the water during infusion. "Dead" water (over-boiled, deoxygenated) results in a flat, flavorless, lifeless tea.
The Korean tradition describes the stages of boiling to guide the right time to use the water:
Shrimp eyes (새우눈, sae-wu-nun): the first small bubbles that appear at the bottom of the kettle, around 70–75°C. This is the ideal moment for delicate Ujeon and Sejak.
Crab eyes (게눈, ge-nun): slightly larger bubbles, around 80–85°C. For Hwangcha and intermediate teas.
Fish boil (어안, eo-an): the water begins to actively simmer, around 90–95°C. For Hongcha and infusions.
The Sookwoo: Respecting the Water Cycle
The Sookwoo (숙우) is the intermediate water pitcher used in the Korean tea ritual. After the kettle, water is poured into the Sookwoo before reaching the teapot and bowls. This intermediate vessel performs several functions simultaneously.
It lowers the water temperature by 8 to 12°C during transfer, which is often enough to go from 85°C to 75°C for a Sejak. It "calms" the water: the molecules agitated by boiling reorganize in the new container, resulting in more homogeneous water temperature. And it allows preheating the bowls by pouring rinsing water into them, a gesture that conditions the first infusion.
Even without a Sookwoo, you can apply this principle: pour boiling water into a cold cup before using it for tea. The act of transferring lowers the temperature and improves homogeneity.
Which Waters to Use in France
| Water | Dry Residue (mg/L) | Suitable for | Note |
|---|---|---|---|
| Mont Roucous | 25 mg/L | All grades, ideal | ⭐⭐⭐⭐⭐ Our recommendation |
| Volvic | 130 mg/L | Sejak, Joongjak, Hongcha | ⭐⭐⭐⭐ Very good |
| Evian | 345 mg/L | Hongcha only | ⭐⭐ Too hard for green teas |
| Filtered Tap Water | 80–150 mg/L | Sejak, Joongjak | ⭐⭐⭐ Acceptable with good pitcher |
| Paris Tap Water | 300–450 mg/L | Not recommended | ⭐ Avoid for fine teas |
The 5 Mistakes to Avoid
Boiling water on green tea
100°C destroys umami compounds and massively releases bitter tannins. Result: bitter and astringent tea.
Wait for 65–75°C
A thermometer or the "shrimp eyes" method ensures the correct temperature for each grade.
Re-boiling water
Re-boiled water loses its dissolved oxygen. The tea will be flat, without aromatic depth.
Fresh water every time
Always start with fresh, unboiled water. Dissolved oxygen is essential for releasing aromas.
Too hard water
Calcium neutralizes the fine aromas of green tea and creates an oily film on the surface.
Soft water < 100 mg/L
Mont Roucous, Volvic, or filtered water with a good pitcher.
Teas to be revealed with good water
Good water enhances the qualities of these exceptional teas.
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Grand crus and accessories selected in Seoul. Code BIENVENUE10 for 10% off your first order.
Grand Crus AccessoriesAbout the author:Nico Lesage is the founder of Maison Boseong. An expert in Korean teas, he has lived in Seoul since 2011. Every year, he travels to the peninsula’s tea gardens to source exceptional harvests directly from local producers.