Flash Brew
What is Flash Brew?
Flash brew is a clever method for iced coffee: you brew coffee hot in a hand filter and replace part of the water with ice. The good thing about it? The iced coffee is ready immediately – no long waiting! Not to be confused with cold brew: here you use cold water and leave the coffee to steep cold in the fridge for several hours or overnight.
With cold brew, the aromas are extracted slowly, which ensures a smooth taste. The idea behind flash brew is that the immediate cooling preserves volatile aromas in the coffee that would otherwise be lost. This captures particularly fruity aromas and the freshness of the coffee – although there are no clear scientific studies on this.
One thing is certain: with this method, you can prepare really aromatic iced coffee super quickly. In this blog post, we show you step by step how to easily make flash brew at home with a hand filter.
Flash Brew Quick Check
Flash Brew Equipment
- Hand filter
- Carafe/glass
- Paper filter
A hand filter such as the Hario V60 is usually used for flash brewing. This is a conical filter attachment made of porcelain, glass or plastic into which you place a paper filter and your freshly ground coffee. You then place the hand filter on a carafe or heat-resistant glass – this is where you simply add the ice for flash brewing.
You can also brew flash brew with a Chemex or other filter methods such as the AeroPress. Depending on the brewing device, you may need to adjust the recipe slightly. As a rule of thumb, about 35 % – 50 % of the brewing water is replaced by ice in the serving vessel.
Flash Brew preparation
Prepare
- get your hand filter ready
- Prepare your water for boiling (approx. 91 °C brewing temperature)
Grind coffee
- grind 30 g of coffee medium-fine
PRO tip: It is best to grind the coffee fresh yourself, e.g. with an adjustable hand grinder.
PRO tip: Have you already found your perfect grind for the hand filter? For flash brew, you can make it a little finer - after all, we use less water than with a pour over.
Prepare water & filter
- Rinse the paper filter with hot water - preferably over a separate container, such as a milk jug, or directly in the sink.
- Fill the serving dish with 135 g ice cubes.
*Please note: With this method, hot coffee comes into direct contact with ice. Your serving vessel must be heat-resistant and suitable for this application!
Broths
Blooming:
- pour the ground coffee into the filter attachment
- pour about 30 ml of hot water onto the coffee bed to wet it evenly
- Leave to soak for 30 seconds
Why: This allows the CO₂ bound in the coffee to escape and extraction is more even.
PRO tip: Place your serving container and your filter with the ground coffee on the scales beforehand and measure. This way, you can easily weigh the water for blooming and brewing.
Infuse:
- slowly pour the remaining hot water (approx. 335 ml) onto the coffee bed in a circular motion
PRO tip: There are also special pouring techniques with graduated brewing times and quantities for infusing in a hand filter - for example, a fast first pour and a particularly slow third pour.
If you are looking for a very detailed recipe with exact brewing times, take a look at these instructions from Kurasu.
Serve
- wait until all the coffee has passed through the filter
- swirl your serving dish briefly for an even temperature
- serve your Flash Brew "on ice"
Flash Brew First Aid
My flash brew tastes watery.
Keep the quantities of water and ice exactly
If you “round up” too much here, the flash brew can quickly become watered down.
Use medium-sized ice
Small ice cubes such as crushed ice melt too quickly and water down your drink.
Check your grind
If your grind is too coarse, the coffee is under-extracted and tastes watery.
If your coffee passes through much too quickly (e.g. only 1 minute instead of approx. 3 minutes), your grind is probably too coarse.
My flash brew tastes bitter/sour.
Check your grind.
If your coffee takes well over 3 minutes to brew, your grind is probably too fine. The coffee is then over-extracted and tastes bitter and sour.
Dilute your flash brew.
If everything went perfectly with the extraction and the coffee is a little too intense for you, you can also add some cold water or milk.
Use a different type of coffee.
It is better to use lighter roasts. If the coffee is roasted too dark, this could also be responsible for the bitter taste.
My Flash Brew is too warm.
Use ice that is big enough.
If your ice cubes are too small, they will melt too quickly and won’t cool your drink well enough.
Rinse your filter paper properly.
If you rinse your paper filter over your serving vessel, you are effectively pre-heating the serving jug. This is great for pour over, but not ideal for flash brew – it’s better to rinse over a different container or in the sink.
Which coffee for Flash Brew
Light roasts made from 100% Arabica are particularly suitable for this brewing method. Flash brew emphasizes the sweet, fruity and floral notes of these coffees. However, medium roasts with chocolate notes can also work well. Darker roasts taste better with cold brew.
Flash Brew advantages and disadvantages
- Advantages
- super quick to make!
- emphasizes the fruity side of coffee
- No special maker required - hand filter is sufficient
- Disadvantages
- slightly more complex than cold brew
- Not suitable for all coffee beans
Flash Brew FAQ
I don't have a hand filter, can I still make flash brew?
You can also try the method without a hand filter. Strictly speaking, this is no longer a flash brew, but you still get a quick iced coffee!
Fully automatic machine: Increase the coffee strength and reduce the amount of water. Pour the coffee directly into a glass with ice cubes.
Portafilter: Place a glass with ice under the portafilter and prepare your espresso shot a little shorter (more like a ristretto) – this way the coffee is less watered down.
Alternatively, you can also try cold brewing. This takes longer, but the result is similarly mild and refreshing.
What is the difference between flash brew and cold brew?
With cold brew, you take cold water and leave the coffee to infuse in the fridge for several hours or overnight. The aromas are extracted slowly, which ensures a smooth taste.
With Flash Brew, you brew hot filter coffee over ice. This cools the iced coffee immediately, which particularly emphasizes the fruity side of the coffee.
Both preparation methods are definitely worth a try and deliver delicious iced coffee!
A really tasty, aromatic iced coffee – ready faster than ever before!
The simple method without special equipment enjoys great popularity in the coffee community for good reason. Immerse yourself in the exciting, aromatic world of Flash Brew and try it out for yourself.
What are you waiting for – your iced coffee will be ready in no time!
