COLD BREWFlash Brew Iced Coffee
The quick answer
Use 20g of coffee with 150g of hot water (94C) and 150g of ice in your brew vessel. Brew pour-over directly onto the ice - hot extraction captures complex, bright flavors that are instantly locked in by rapid chilling. Total ratio is 1:15 coffee to water. Ready in under 5 minutes with no waiting required.
Flash brew is what coffee professionals drink when they want iced coffee and do not have 18 hours to wait for cold brew. It takes four minutes and tastes completely different - brighter, more complex, and more alive.
The method is simple: brew hot coffee directly onto a bed of ice. The hot brew extracts the full aromatic complexity and brightness that cold water can't. The ice immediately chills the coffee, locking in volatile aromatics that would normally dissipate as hot coffee cools on its own. The result is a crisp, clear, bright iced coffee.
Ratio math is the key to avoiding watered-down flash brew. Your total water equals hot brew water plus the weight of the ice (which melts into the coffee). A typical ratio is 1:15 coffee to total water. For 20g of coffee: use 150g of hot water to brew over 150g of ice - the melted ice accounts for the remaining water.
Grind size should match your brewing method. If using a V60 or Chemex, use a medium-fine grind (slightly finer than your normal hot pour-over grind). The smaller amount of hot water means less contact time, so a slightly finer grind ensures full extraction before the water passes through the grounds.
Coffee selection matters more in flash brew than in cold brew. Since you are brewing hot, the full flavor spectrum comes through - including acidity and fruit notes. Light and medium roasts with citrus or stone fruit notes shine in flash brew. Dark roasts can taste flat without the mellowing effect of cold steep time.
Dial it in before you make it
Get the coffee-to-water ratio right for concentrate or ready-to-drink.
| Ingredient | Amount |
|---|---|
| Coffee grounds | 189.6 g |
| Coffee grounds (tablespoons) | 35.8 tbsp |
| Water | 948 g |
| Water (cups) | 4.00 cups |
Serving tip
Dilute 1:1 with water or milk to serve — this batch makes ~8.0 cups of ready-to-drink cold brew.
1 tbsp ground coffee ≈ 5.3 g · 1 cup water = 237 g · 1 fl oz water = 29.57 g. Steep 12–24 h in the refrigerator.
Make it
Makes 1 drink
Ingredients
Steps
We use flash brew for single-cup iced coffee when we have not planned ahead. The brightness and complexity it captures from a well-sourced light roast is something cold brew simply cannot replicate - it is a different experience worth trying alongside your regular cold brew routine.
Pro tips
- Use a light or medium roast coffee - flash brew highlights acidity and brightness that cold brew suppresses.
- Weigh your ice and hot water separately to hit the 1:15 total ratio accurately every time.
- Brew slightly faster than your normal pour-over pace to avoid over-extraction with the smaller water volume.
- Flash brew does not keep well - drink it within a few hours for the best flavor.
- Compare flash brew and cold brew side-by-side using the same coffee to understand what extraction temperature actually does.
Frequently asked questions
What is flash brew iced coffee?
Flash brew is a method where you brew hot coffee (using pour-over or drip) directly onto ice. The hot extraction captures full flavor complexity, and the ice instantly chills the coffee before aromatics can dissipate.
What is the ratio for flash brew iced coffee?
A 1:15 coffee-to-total-water ratio, split between hot brew water and ice. For 20g of coffee: 150g hot water plus 150g ice equals 300g total water, which maintains the standard 1:15 brewing ratio.
Is flash brew better than cold brew?
They taste completely different. Flash brew is brighter, more acidic, and more complex. Cold brew is smoother and lower in acid. Neither is objectively better - it depends on what you want from your iced coffee.
Can I make flash brew with a drip coffee maker?
Some drip machines have an iced coffee setting that brews at double strength. If yours does not, place ice directly in the carafe and run a shorter, more concentrated brew cycle using half the normal water amount.
Does flash brew have more caffeine than cold brew?
Caffeine per serving is roughly comparable between flash brew and diluted cold brew. Flash brew at a 1:15 ratio is similar in strength to any standard cup of drip coffee served over ice.
