The Art of Cold Brew: Crafting the Perfect Iced Green Tea for Sunny Days
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The Art of Cold Brew: The Perfect Iced Korean Green Tea
The naengchim method, Korean cold brewing, produces a bitterness-free result that no other technique can imitate.
By Maison Boseong · Seoul · 8 min read
With the arrival of warmer days, Seoul's tea houses transform. Hot Sejak turns into a silky, emerald green liquor, free from any bitterness. It's chemistry and a centuries-old Korean technique.
1. The Naengchim method
In Korea, the technique 냉침 (naengchim, cold infusion) has been documented since the Joseon period. Rather than extracting with heat, cold water is allowed to work slowly. The result is chemically different from cooled hot tea.
2. Why cold changes everything
Boiling water simultaneously extracts delicate aromas and bitter tannins. Cold water is selective: at 4–10°C, it favors sweet aromatic compounds, leaving tannins in the leaf.
Fast and complete extraction
Aromas and tannins extracted together. Bitterness present.
Slow and selective extraction
Only sweet aromas. Zero bitterness.
3. Which tea to choose?
The higher the quality of the tea, the better the cold brew will be. First flush spring teas, Sejak and Ujeon, are the ideal candidates.
4. Recipe 1: Classic Sejak Cold Brew
Ingredients
- Sejak leaves or tea bags10–15g / 3–4
- Filtered cold water1 liter
- Ice cubes when servingto taste
Preparation
- Place leaves in a glass carafe.
- Pour 1L of cold water without stirring.
- Refrigerate for 6 to 8 hours.
- Filter without pressing. Serve over ice.
5. Recipe 2: Overnight Ujeon Cold Brew
Ingredients
- Loose-leaf Ujeon5g
- Low mineral cold water500ml
Preparation
- Place leaves in a carafe. Pour water.
- Refrigerate overnight, 10 to 12 hours.
- Gently filter. Serve chilled, plain.
6. Recipe 3: Iced Korean Matcha Latte
Ingredients
- Sifted Korean Matcha2g
- Hot water30ml at 70°C
- Cold oat milk200ml
- Ice cubes1 large glass
Preparation
- Sift matcha, whisk with water until smooth paste.
- Fill a glass with ice cubes. Pour in cold milk.
- Drizzle matcha paste. Mix before drinking.
7. Key parameters
| Parameter | Value | Impact |
|---|---|---|
| Water temperature | 4 to 10°C | Colder = more selective |
| Water mineral content | < 150 mg/L | Hard water masks aromas |
| Dosing | 10–15g/L | Under-dosing = flatness |
| Sejak steeping time | 6 to 8 hours | Beyond 12h: bitterness |
| Filtration | Without pressing | Pressing releases tannins |
8. Summer variations
Sparkling Sejak
Replace water with sparkling water when serving.
Lemon-Yuzu Sejak
Add a spoon of yuzu jam to the glass.
Honey Cold Brew
Dissolve a spoonful of acacia honey before refrigeration.
Cucumber-Mint Sejak
Infuse 2 cucumber slices and 3 mint leaves.
Frequently Asked Questions about Korean Cold Brew
What is the difference between a cold brew and a cooled hot tea?
A cooled hot tea has already extracted all its bitter tannins. Cold brew extracts cold from the start. Cold water selectively extracts only the sweet aromatic compounds. The result is completely different, milder, without bitterness.
Can any Korean tea be used for cold brew?
Technically yes, but first flush green teas (Ujeon, Sejak) give the best results. Boricha as cold brew is also excellent.
How long does Korean cold brew last?
48 to 72 hours in the refrigerator in an airtight container.
What water should I use?
Low mineralized water, below 150 mg/L. Volvic (109 mg/L) is a good choice.
About 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.