Flash Brew vs Cold Brew Iced Coffee: What's the Difference

Introduction

HCMC's hot climate makes iced coffee a daily necessity. There are two main ways to make iced coffee at home: flash brew and cold brew.

This article compares both methods, provides step-by-step instructions, and helps you choose the best fit for life in HCMC.

What is flash brew

Flash brew drips hot coffee directly onto ice for instant cooling. The dominant method in Japan, it locks in aroma and bright acidity through rapid chilling.

Characteristics:

• Hot water extracts full aroma compounds
• Rapid ice cooling traps aromatics before they dissipate
• Bright acidity and aromatic fragrance
• Ready to drink immediately

What is cold brew

Cold brew steeps coffee in room-temperature or cold water over many hours. Recently popular at cafes and convenience stores in Japan.

Characteristics:

• No heat means less bitterness and off-flavors
• Smooth, sweet taste
• Light body, easy to drink
• Requires 8-24 hours of extraction

Comparison

Criteria	Flash brew	Cold brew
Extraction temp	90-96°C (hot)	Room temp or cold
Time	3-5 min	8-24 hours
Flavor profile	Bright aroma, vivid acidity	Smooth, sweet, clean
Bitterness	Depends on roast	Mild
Best beans	Light to medium roast	Medium to dark roast
Convenience	Instant	Requires advance prep
Storage	Drink same day	Fridge for 2-3 days

How to make flash brew

What you need

• Dripper and paper filter
• Coffee grounds (medium): 20-25g
• Hot water: about 150ml
• Ice: about 100-120g
• Server or glass
• Gooseneck kettle

Steps

1. Fill server with ice. Ice amount should be 60-80% of hot water volume.
2. Set dripper on server and add grounds. Use more grounds than usual (ice will dilute).
3. Bloom: Pour 30-40ml hot water, wait 30 seconds.
4. Pour: Add remaining hot water slowly. You'll hear it sizzle as it hits the ice.
5. Remove dripper, stir gently, done.

Key point: brew stronger than normal since ice will dilute the coffee.

How to make cold brew

What you need

• Cold brew pitcher (or jar/bottle)
• Coffee grounds (medium to slightly coarse): 60-80g
• Water: 700-1000ml
• Tea bag filter (if no dedicated pitcher)

Steps

1. Add grounds to the pitcher's filter. No pitcher? Put grounds in a tea bag and drop in a bottle.
2. Add water. Room temp water extracts slightly faster; cold water yields smoother results.
3. Refrigerate 8-12 hours. Set up at night, ready by morning.
4. Remove the filter (or tea bag). Done. Leaving grounds in too long causes over-extraction.

Which suits HCMC?

HCMC is hot year-round, making iced coffee a major need.

• Flash brew works when: You want coffee now, or want to showcase light-roast aromas
• Cold brew works when: You want to batch-prep, or prefer a smooth, mellow flavor

Batch cold brew on weekends, just pour in the morning on weekdays. Flash brew for same-day, cold brew keeps 2-3 days in the fridge.

Compared to Vietnamese iced coffee

Vietnamese ca phe sua da uses a phin to brew strong coffee, then combines it with condensed milk and ice. A different approach from flash brew or cold brew, each has its charm. Try switching between them based on your mood.

Find coffee on Farmi

The Farmi app offers coffee beans and drip bags suited for iced coffee. Delivered to your door in HCMC. Download Farmi and discover your favorite iced coffee style.

Note: This article and some images were created with the assistance of AI (artificial intelligence) and reviewed by the editorial team before publication.