Cold brew works by steeping coffee in cold water for twelve to twenty-four hours. It produces something smooth, low in acidity and, honestly, a little anonymous. Cold water never extracts the delicate aromatic compounds at all — they stay in the grounds and go in the trash.
Flash brew takes the opposite approach. You brew hot, using roughly half the usual water, directly onto ice that makes up the difference. The extraction is complete, and the sudden chill traps the aromatics in the liquid instead of letting them escape as steam.
It takes four minutes and it tastes like the coffee you actually bought.
The ratio
The rule is simple: replace 40% of your brew water with ice, by weight.
- 22 g of coffee, medium-fine grind
- 220 g of hot water at 200°F
- 140 g of ice, in the carafe before you start
Total liquid lands around 360 g, the same as a standard pour-over.
The method
- Weigh the ice into your carafe or server first. Not into the glass — into the vessel the coffee drips into.
- Set your dripper on top and rinse the filter. Discard the rinse water without melting your ice.
- Add the coffee. Bloom with 45 g of water for 40 seconds.
- Pour the remaining water in two slow spirals. Same technique as a hot pour-over.
- Swirl when it finishes. The last of the ice should melt as you do. If ice is still floating, add a little more water; if it is fully gone before you swirl, use more ice next time.
- Pour over fresh ice and drink immediately.
Which coffee
Cenicafé, medium roast. Flash brew rewards acidity and aromatics, and its citrus and honey notes come through cleanly over ice — brighter and more defined than they read hot. Dark roasts turn ashy when chilled this way.
Variations
Flash brew tonic. Half flash brew, half tonic water over ice, with an orange peel. The citrus in Cenicafé does most of the work.
Flash brew with a splash of milk. Oat milk in particular sits well with the honey and hazelnut notes.
Flash brew from a drip bag. Brew a Bosa Coffee Drip directly onto 60 g of ice in a glass, using a little over half the usual water. Fastest iced coffee possible.
Why we keep coming back to this one
Flash brew was the single best-performing thing we published all year. It is fast, it is visual, and it converts people who assumed iced coffee had to be either watery or bitter. If you try one method from this series, make it this one.
See the full brewing guide for the other five methods.