Flash brew, also known as Japanese-style iced coffee, is hot coffee brewed straight over ice. The fast chill keeps the bright acidity and aroma that a long cold steep tends to soften, and the whole thing takes minutes rather than hours.
What is flash brew coffee?
Flash brew is a quick method that brews coffee with hot water and chills it straight away. Hot water pulls out the coffee's fruit and floral notes, and chilling it quickly leaves less time for bitterness and oxidation to set in.
Unlike cold brew, which steeps in cold water for 12 to 18 hours, flash brew is ready in minutes. The cup is clean and crisp.
Why use permanent ice cubes?
We flash brew over permanent ice cubes, made from stainless steel or food-safe plastic. They chill the coffee without diluting it, so the cup tastes the same from first sip to last.
Flash brew recipe by Katie, Ozone's Customer Support Manager
Katie Glover, our Customer Support Manager, shared her go-to flash brew method for iced coffee at home. Here it is, step by step.
Ingredients and equipment
- 21g coffee, coarse filter grind (Katie uses 10 clicks on a Porlex grinder)
- 300g water at 92°C
- Reusable ice cubes (plastic or stainless steel)
- Large Clever Dripper
- 2 carafes (a glass server like this Kalita works well)
- Paper filter
Brewing instructions
- Place a paper filter in the Clever Dripper and rinse it with hot water. Discard the rinse water.
- Divide your reusable ice cubes between the two carafes: 200g in the first, 150g in the second.
- Fill the Clever Dripper with 300g of hot water. Add the ground coffee and stir until all the grounds are wet.
- Let the coffee steep. Stir again at 1:30.
- At 3:00, place the Clever Dripper on the first carafe to drain.
- Let the coffee sit in the first carafe for 3 minutes, stirring now and then to cool it further.
- Pour the coffee into the second carafe for an extra chill. Look for condensation on the glass as a sign it's ready.
Frequently asked questions
What's the difference between flash brew and cold brew?
Flash brew uses hot water and brews straight over ice, which keeps the coffee's acidity and aroma bright. Cold brew steeps in cold water for 12 to 18 hours. That gives a smoother, less acidic cup, and a different flavour.
Can I use regular ice instead of permanent ice cubes?
Yes, but regular ice melts into the coffee and dilutes it. Brew a little stronger to compensate, using a touch more coffee for the same water.
What type of coffee works best for flash brew?
Light to medium roasts work well, especially coffees with fruity or floral notes. Brewing hot over ice keeps those notes bright.
Do I need a Clever Dripper?
No. A Kalita Wave, V60, Chemex or AeroPress all work. Keep an eye on brew time and chill the coffee quickly.
Is flash brew stronger than cold brew?
It depends on the recipe. Flash brew tastes brighter and more complex. Caffeine comes down to the coffee dose, the ratio and the brew time, so it varies more by recipe than by method.
