The fastest way to a high-quality cold coffee is also the most counter-intuitive: brew a hot V60 directly onto ice. Flash brew (sometimes called Japanese iced or Tetsu Kasuya iced, after the WBrC 2016 champion who popularised it) replaces part of the brew water with ice in the carafe. The hot brew falls through the bed normally, then chills instantly on contact with ice — locking the volatile aromatics in the cup before they evaporate.
How it differs from cold brew
These are two different drinks, not two formats of the same one:
- Cold brew uses cold water for hours. No heat means no extraction of bright, volatile compounds. The cup is low-acid, chocolate-leaning, heavy.
- Japanese iced uses hot water briefly, then chills the brew. Heat extracts the brightness; the ice locks it. The cup keeps the floral, citric, juicy notes a hot V60 would give you.
If you love your V60 hot, Japanese iced is the closest cold version of that same coffee. Cold brew is a different cup.
The recipe
Standard recipe for a single serving:
- Coffee: 15 g, V60 grind (slightly finer than usual to compensate for the smaller water volume).
- Total water: 250 g, of which:
- 150 g hot water in the kettle, ~94 °C.
- 100 g ice in the carafe before brewing starts.
- Ratio note: the total still reads as 1:16.7 (15 g to 250 g of water + ice combined) — but the hot extraction phase only sees 150 g of water at 1:10. That higher concentration is on purpose; the meltwater dilutes it back to drinking strength.
How to brew it
- Place ice cubes (100 g, weighed) in the V60's server or carafe.
- Set the V60 on top of the ice-loaded carafe.
- Add coffee and tare the scale.
- Bloom: 30 g hot water (2x the coffee), 30–45 seconds.
- Main pour: continuous spiral or pulses, totalling 150 g hot water (so 120 g more after the bloom). Aim to finish pouring around 1:30.
- Drawdown completes around 2:30. The brew lands directly on the ice and chills instantly.
- Swirl the carafe to dissolve any remaining ice and even out the temperature.
- Pour over fresh ice in a glass if you want a colder serve.
What goes wrong
- Not enough ice in the carafe: the brew lands warm, doesn't lock the aromatics. The cup tastes weaker than expected.
- Too much ice: doesn't fully melt, dilutes the cup. Weigh the ice; don't eyeball it.
- Ice in the wrong place: ice on top of the coffee bed or in the V60 itself doesn't work. The ice must be in the server, downstream of the brew, so the hot brew chills only after extraction.
- Same recipe as a hot V60: ratios that work hot don't work flash. The extraction phase needs to be over-strong because the meltwater is going to dilute it.
When to reach for it
Hot weather. When you have a great single-origin you don't want to "waste" on cold brew. When you want a cold coffee in 3 minutes instead of 12 hours. As a way to taste origin character through cold serving — a flash-brewed Ethiopia keeps its florals; a cold brew of the same bag does not.
Variants
The Tetsu Kasuya 4:6 method translates to flash brew with one adjustment: keep the 40/60 split, but apply it only to the hot 150 g portion. The competition-grade version uses the same ratios as standard 4:6 with ice replacing 40% of the water — it's the recipe Kasuya brewed at his championship.