• Photo of two glasses of iced cold brew coffee next to a potted plant.


Guide To Flash Brew Coffee

There are many ways to make coffee cold, but we believe one method stands above the rest: flash brew! It’s delicious, made to order, and helps get the best out of our beans. But don’t take our word for it—follow the recipe and tips below to see for yourself.

There are many ways to make coffee cold, but we believe one method stands above the rest: flash brew! It’s delicious, made to order, and helps get the best out of our beans. But don’t take our word for it—follow the recipe and tips below to see for yourself.

In the past, we referred to this method as Japanese Iced Coffee. Buzzfeed even credits us as the coffee company who brought this technique to the US in the late '90s. Whether this method is flying under the radar or blowing up on TikTok, it's always been our favorite way to make cold coffee. 

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  • Cold Brew Vs. Flash Brew

    While cold brew is great, it has a time and place. Flash brew is for when you want cold coffee ASAP. To make cold brew, you combine your coffee and water and let it "steep" or "extract" for a long period of time, usually overnight, in your refrigerator. At no point are you heating water which is why it takes longer. 

    One of the biggest obstacles to the deliciousness of coffee is time. If coffee sits for a long time cooling (or brewing!), you’ll end up with oxidized, off flavors. Not ideal. Flash brew produces perfectly-balanced, ready-to-drink iced coffee, in a FLASH!

    Close up photo of ice in a Chemex.

    What Is Flash Brew?

    When flash brewing, you make you use basic pour-over brewing equipment to create a coffee concentrate before adding ice. Adding ice to the hot concentrate does two important things: it dilutes and chills the coffee quickly! This is our favorite method to brew iced coffee because the hot water really brings out the coffees flavors and the fast cooling locks it in.

    Melting ice adds to the total water volume without weakening the final brew. Fast, intuitive, and delicious, we can’t think of a better way to enjoy coffee when temperatures soar.

    What You'll Need To Make Flash Brew Coffee

    As with every brew method, use freshly roasted, whole-bean coffee. Doing so will yield more of the sweetness and aroma that we all seek in a cup of coffee, whether cold or hot. This flash brew recipe maximizes and locks in that flavor potential.

    The equipment required to make flash brew is going to be identical to your normal pour over setup. This includes the brewing device, kettle, scale, filter, and serving vessel. Some of our favorites are the Kalita Wave, a Hario V60, a Bonmac, and a Chemex, but any pour over brewing device will do! Our recommendations are the ones we have tried and tested and gotten the best results from.

    Photo of coffee being poured into a glass filled with ice.

    Steps To Making Flash Brew Coffee

    Step 1: Heat Your Water

    Before setting up your device, start boiling your water. Heating up the water takes a while, so you can do the rest of the setup while you wait. Since water makes up 98% of a cup of coffee, water quality is important. We recommend using filtered water. A simple Brita filter is perfect for removing any flavor or odor that might be present in your tap water.

    As a rule of thumb, bring your kettle to a full boil—212˚ F. This is going to give you the most consistent results and will work well for most coffees. If you just KNOW that a slightly cooler temperature works better for your coffee, and you have the ability to be precise with the water temperature on your kettle, you brew you!

    Step 2: Weigh And Grind Your Coffee

    Photo of coffee grounds in a filter in a pour-over device.

    Next, your going to weigh and grind your coffee. You can use the same brew ratio you would normally use for making hot coffee. Our preference is something around 1:17. That is 1 gram of coffee for every 17 grams of water. For this example, we are going to use a Kalita 185 with 30 grams of coffee and 500 grams of water. If you prefer stronger or weaker coffee, feel free to adjust accordingly.

    An adjustable burr grinder is a must here to get the freshest tasting coffee. You can be a little experimental with your grinding and figure out what works best for you. Try it one way and assess the taste. If the flavor seems a little off, you can always make an adjustment next time. We know there will be plenty of opportunities this summer!

    For flash brew, we usually grind at the same setting we’d use for hot coffee, but sometimes you can get a better result by grinding a touch finer. Medium-coarse is the usual standard in a Kalita Wave, but brewer’s choice here.

    Once your coffee is ground, add it to the filter in your device and give a gentle shake to level out the grounds. 

    Step 3: Brew Your Coffee

    Photo of a chemex with a leather wrap sitting on a scale in a kitchen.

    Now let’s get into the details! As we said in the beginning, to make flash brew we dilute it with ice. So, to brew we will be using only two-thirds the amount of hot water that we would normally use for hot coffee with the final third added as ice.

    Using our 30 grams of coffee and 500 grams of water recipe, we are going to pour only 365 grams of water and use about 135 grams of ice. Follow your usual brewing steps, but only pour a total of 365g of water. After all the water passes through, add ice in place of the remaining one-third of water. Some people put the ice in their brewing vessel or chemex first so the coffee drips onto it. We prefer to brew first and then add the ice. That is the same recommendation we make when making an iced espresso drink.

    One note: try to keep the brew time as close to your usual one as possible. For the Kalita, we’re aiming for a 3:30 brew time. To achieve this same brew time while using less water, you’re going to need to try to slow down that pour.

    There are a lot of cold coffee brewing methods out there, but we highly recommend giving this one a try. Let us know what YOU think. If you want to learn more, check out our brewing classes at a training center near you. Happy brewing!

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