What Is Rei Matcha? How to Make Cold Matcha the Right Way (and When to Break the Rules)

Rei Matcha is cold matcha, made by preparing a standard usucha (thin matcha with hot water) and then pouring it over ice. The hot-water-first method is recommended for quality matcha because hot water extracts the full flavour complexity, including umami, sweetness, and layered notes, before the ice cools it down. For lower-quality matcha with noticeable astringency, mixing directly with cold water is the better approach, because cold water limits catechin extraction and keeps the astringency in check.

Behind The Leaves #48

What Rei Matcha Is and How It Differs from Iced Matcha Americano

Rei Matcha literally means cold matcha. It is made the same way as usucha, the traditional thin preparation of matcha, and then served over ice. The drink retains the full concentration of the matcha flavour rather than being diluted further with additional water.

The iced matcha americano is different in a few ways. It typically uses more water, making it thinner in body and lighter in intensity. The Rei Matcha is closer to the original matcha experience: you are tasting the tea itself, chilled, rather than a diluted version. For this reason, the quality of the matcha you use matters more in Rei Matcha than it would in a milk-based matcha drink. The foam difference is also notable: because Rei Matcha is made as a full usucha first, it can retain a thick layer of microfoam on top of the glass if you whisk deliberately for it.

The Standard Method: Hot Water First, Then Ice

The preferred preparation for quality matcha is:

Start by making a matcha paste. Combine 2 grams of matcha with 10ml of room temperature water and mix until completely smooth. This paste step is what ensures the final drink has no clumps regardless of whether you sift the powder first. The aroma lifts noticeably during this step, which is part of the pleasure of making it.

Add 50ml of water at 80 degrees Celsius to the paste and whisk it as you would a normal usucha. The foam you create at this stage will survive the transition to cold surprisingly well. Pour or spoon the finished matcha over a glass of ice. The drink is ready once it has cooled down enough to drink, which happens quickly.

The reason hot water is used rather than cold water directly comes down to extraction. At 80 degrees, the amino acids responsible for umami and sweetness extract fully, along with the complex layered flavour compounds that make a premium matcha interesting to drink. Cooling the drink with ice afterward does not reverse that extraction. What you get is a cold matcha that retains the full character of the tea, not a flattened, simpler version of it.

Why Matcha Grade Determines Which Method You Should Use

Here is where the method becomes strategic rather than routine.

For premium matcha like the Wako by Marukyu Koyamaen, hot-water extraction makes complete sense. The tea has low natural astringency, high sweetness and umami, and complex layered notes. Hot water allows you to extract all of those qualities, and the result is a cold drink that is smooth, layered, and genuinely delicious.

For a lower-grade matcha with pronounced astringency, the hot-water method actually works against you. Higher water temperatures extract more catechins, which are the compounds primarily responsible for astringency. Making a hot usucha from a strongly astringent matcha and then chilling it gives you a cold drink that is still quite astringent. The cold format makes the astringency more noticeable, not less, because there is no milk or sweetener to soften it.

In that case, mixing the matcha directly with cold water from the start is the better approach. Cold water suppresses catechin extraction, which reduces the astringency in the final cup. You lose some of the complex flavour notes, but if those notes are not there to begin with in a lower-grade matcha, the trade-off is worth it. The cup becomes cleaner and more drinkable.

The decision tree is simple: premium matcha with low astringency means hot water first. Entry-grade or culinary matcha with noticeable astringency means cold water from the start.

The Freezer Method: Tested and Honest Assessment

One alternative approach that circulates online is to make the hot usucha as normal, then place it in the freezer for 30 minutes rather than pouring it over ice. The appeal is obvious: no dilution from melting ice, so the matcha stays at full concentration throughout.

This method was tested directly. The result was not unpleasant, but there was a practical problem: the matcha picked up the smell of the freezer. Even with a relatively new freezer used exclusively for sealed matcha storage, the odour transferred noticeably. In a typical home freezer with a broader variety of frozen foods, this problem would almost certainly be worse.

For this reason, the traditional Rei Matcha method (hot usucha poured over ice) is still recommended as the better approach in most home settings. The slight dilution from melting ice is a much smaller drawback than having your matcha absorb freezer odours.

Key Takeaways

Rei Matcha is usucha made with hot water and then poured over ice. It is not just chilled matcha. The hot-water preparation step is what determines the quality of the final cold drink.

Hot water first extracts more flavour complexity, including umami, sweetness, and layered notes. Cooling the matcha with ice afterward does not undo that extraction. For premium matcha, this method is significantly better.

For lower-grade or strongly astringent matcha, cold water from the start is the smarter choice. Cold water limits catechin extraction, keeping astringency in check. The trade-off is a flatter flavour profile, but that is often a better outcome than a cold drink dominated by astringency.

The freezer method avoids dilution but introduces freezer odour. It was tested directly and found to produce a detectable off-smell even in a well-maintained freezer. Not recommended as a practical home method.

The microfoam from a well-made usucha survives the pour onto ice. This is worth knowing if foam texture matters to you in a cold matcha presentation.

Insights From Yuki

The Wako by Marukyu Koyamaen was used for this session, a high-level usucha grade matcha that is also suitable for koicha preparation. On tasting the finished Rei Matcha, the sweetness, umami, and layered bright notes were all clearly present in the cold cup. The astringency remained very low. This confirmed that hot-water extraction followed by icing preserves the character of a premium matcha effectively.

One key observation from the freezer test: even a relatively clean, dedicated matcha freezer transferred a detectable odour to the drink within 30 minutes. This is worth taking seriously for anyone considering the freezer method as a no-dilution shortcut. Matcha is highly sensitive to odour absorption, which is also why proper sealed storage matters so much for matcha generally.

One key practical observation: the paste step (mixing the dry powder with a small amount of room temperature water first) was confirmed as an effective substitute for sifting. Once the paste is smooth, there are no clumps in the final drink regardless of whether the powder was sifted beforehand. This is a useful efficiency in home preparation where washing a sieve is an added annoyance.

Q&A

What is Rei Matcha?

Rei Matcha is cold matcha, made by preparing a standard usucha (traditional thin matcha with hot water) and then pouring it over ice. It retains the full concentration and flavour of the matcha, unlike an iced matcha americano which is more diluted.

Should you use hot water or cold water to make iced matcha?

It depends on the grade of your matcha. For premium matcha with low astringency, use hot water at 80 degrees Celsius first, then pour over ice. The hot extraction captures the full flavour complexity, which survives cooling. For lower-grade matcha with noticeable astringency, use cold water directly, as this limits catechin extraction and produces a less astringent result.

Does pouring matcha over ice dilute the flavour?

Yes, to a small degree as the ice melts. The flavour of a hot usucha is more concentrated than the final Rei Matcha because of this dilution. However, the flavour compounds extracted during the hot whisking phase are already in the liquid before the ice is added, so the key flavour characteristics remain. The alternative of using a freezer instead of ice introduces freezer odours, which is a worse trade-off than minor dilution.

About the author:

Yuki Ishii
Founder & CEO of Tealife
LinkedIn | YouTube

Yuki is the founder of Tealife, a Singapore-based Japanese tea company. He’s passionate about Japanese tea and spends his time testing, trying, and experimenting - then sharing what he learns through content to help people discover the depth of Japanese tea beyond just matcha.