Flash Brew Coffee 101

Flash Brew Coffee—also widely known as Japanese Iced Coffee (“aisu kōhī”) outside of the U.S.—is a standalone iced coffee beverage and brewing technique that takes advantage of freshly brewed coffee’s boiling temperature through an ingenious use of physics.

Unlike cold brew or iced espresso, for instance, flash brewing intentionally uses a pour over’s hot coffee to melt pre-measured ice within the pour over’s carafe during brewing.

The purpose of this brewing method is two-fold: 1. Combining hot coffee with fresh ice instantly cools the coffee to a drinkable room temp that can quickly be served, and 2. Using a pre-measured amount of ice combined with a pre-measured amount of boiling water maintains a 1:16 ration of coffee to water, which avoids accidental dilution after serving.

Here at Alma Coffee, we’ve found flash brew to be an excellent alternative to cold brew concentrate not just for the reasons listed above, but also because it brings out fruity and floral tasting notes in our own light roast coffees that typically remain subtle in other iced forms (try our Honey Process over flash brew to see exactly what we mean by this).

So, has the concept of flash brewing peaked your interest? We have some good news for those seeking to taste the flash brew difference in their own favorite coffees.

Compared to traditional manual pour overs that can quickly become tedious, flash brewing is one of the easiest and fastest manual brewing techniques we’ve ever come across in our coffee roasting careers. Keep scrolling to see how you can easily flash brew right from your own at-home coffee bar!

As we previously mentioned, one of the main reasons we’ve come to love flash brew here at Alma has to do with the simplicity of the brewing process. Before we walk you through this process, however, you’re going to want to make sure you have the following at-home manual brewing equipment to get the job done.

- Hario Hot n’ Iced Brewer OR Hario V60 Brewer

- Hario V60 Filters

- Coffee Scale (set to metric grams)

- Gooseneck Water Kettle

- Freshly Roasted Coffee Beans (ground to medium-fine)

- (Optional) Burr Coffee Grinder

Got everything you need to flash brew at home? That’s cap!

You can get started now by following along from home with the steps listed below and/or watching our own Flash Brew Coffee Guide video now which follows this exact same recipe (click the video thumbnail below). Keep in mind that practice makes perfect, so give yourself a few tries, taste tests, or recipe alterations until you find that perfect icy cup…

Start off by boiling a kettle of water, prepping—or freshly grinding—26 grams of medium-fine coffee, and pre-wetting your V60 filter on the filter bed in order to remove any paper taste/residue before brewing.

Discard any excess water from pre-wetting the filter, put the ice chamber within the carafe (if using the Hot n’ Iced brewer), then add approximately 130 grams of fresh ice to your Hario brewing device.

Once the ice is added, place the V60 filter bed with the pre-wetted filter on top of your Hario brewing device and add 26 grams of medium fine coffee in the filter bed.

Be sure to aim for the center of the filter bed when adding coffee grounds and avoid spilling onto the sides, as it will lead to uneven extraction of coffee in the upcoming steps.

After all 26 grams have been added, flatten your bed of coffee grounds before moving on to Step 3.

Now that everything is in place, it’s time to bloom your coffee!

Carefully pour between 50-60 grams of water evenly over your bed of coffee grounds, being sure to not leave any dry spots across the entire surface. Now, wait 30 seconds for your coffee to “bloom” before moving on to step 4!

Pssst… If you don’t know what coffee blooming is or why it’s important for pour over brewing, check out our blog on the science of coffee blooming by visiting the button below.

Once the coffee finishes blooming (usually when you stop seeing gas bubbles rise to the surface after 30-45 seconds), it’s time to add the remaining boiling water in a rotating motion until you reach 226 total grams of added boiling water.

In short, the best way to evenly extract all those delicious flavors out of your coffee is to ensure the grinds are spending just the right amount of time in the boiling hot water during this step.

We’ve found our own “goldilocks” coffee extraction time to be around 2-3 minutes for flash brewed coffee, which is achieved by adding 50-80 grams of boiling water every 30 seconds until you get to 226 total grams.

Even the slightest variations in this final step of the pour over process will drastically change the flavor within your final cup, so we encourage you to experiment with the timing, frequency, and pour interval of boiling water until you find your perfect cup.

Once the coffee finishes pouring from the filter bed and all the ice has melted, it’s time to enjoy your first cup of flash brew. Cheers!

We recommend serving this fresh karaf of coffee over ice as soon as brewing is finished to enjoy the freshly extracted flavors in their best state (pro tip: if you’re looking for the perfect serving glass, this recipe fits snugly in our iconic Alma Can Glass).

One of our favorite parts of flash brew is its shelf life, you can keep your batch in the fridge for about 3 days and it will still taste amazing! Albeit, if you enjoy flash brew as much as we do, you’ll find it will disappear pretty quickly :)

What do you think of flash brew coffee? Is it something you think you’ll be sipping on this summer, or does cold brew still have your heart? Let us know in the comments below, and as always be sure to subscribe to our email newsletter to get notified when our latest coffee blog content drops. 

Happy flash brewing, coffee lovers!