Last month our HQ training room turned into a cold brew laboratory. As the warmer weather rolled in, it felt like the perfect time to explore cold brew. That’s why we wanted to deep dive into all things cold brew. We learnt all about different variables and how they affect your final cup. It was a great and insightful evening spent with our community learning about the nuances of cold brewing and tasting the final smooth results.
What is Cold Brew?
Most coffee brewing methods rely on hot water, for instance, everyone’s favourite espresso. Today, however, we put the spotlight on cold brew. Cold brew coffee is made by steeping coarse coffee grounds in cold water for an extended period of time. The drastic difference in the water temperature makes the amount of time it takes to brew espresso and cold brew completely different. Espresso usually takes around 30 seconds and depending what other brewing method you’re using it takes 2 to 5 minutes to fill a mug. Cold brew, on the other hand, usually takes 12-24 hours to brew, depending on your liking. After steeping, the mixture is filtered to remove the grounds, leading to a clean, light-bodied, tea-like coffee. Unlike traditional brewing methods that use hot water, cold brew extracts flavours more slowly. This gives it a few distinctive traits. Cold brew results in a smooth, low-acidity and, surprisingly, highly caffeinated coffee.
Most cuppings focus on hot coffee, making this cold cupping tasting a unique experience just in itself. On top of that, we did something different this time and conducted a guided tasting, which our cupping guests found more helpful than the usual open table sipping.
The preparation
We were curious to find out which variables have the biggest impact on the flavour of a cold brew. Does brewing time make the biggest difference? What about the coffee's processing method, the brewing temperature or the coffee-to-water ratio?
Before the session, our Barista Trainer Sujan and the Midnight Oil Drinks team brewed a range of cold brews to put a few key variables to the test. We experimented with brewing time, temperature, coffee-to-water ratio and a selection of coffees, including The Estate, The Baron and The Fields. Each coffee was brewed for 12, 18 and 21 hours, allowing us to compare how time and recipe changes shaped the final cup.
Our Findings from the Test
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How did the coffee-to-water ratio affect the flavour? A stronger ratio created a fuller-bodied, more intense cold brew, while a more diluted recipe highlighted clarity and made the coffee feel lighter and more refreshing.
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How did brewing time change the cup? Shorter brewing times brought out brighter, sweeter notes, whereas longer extractions developed deeper chocolate and nut flavours, although brewing for too long risked introducing drier, more bitter characteristics.
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How did temperature influence extraction? We also explored the difference between brewing in the fridge and at room temperature. A slower, chilled extraction generally produced a cleaner, softer profile, while room-temperature brewing extracted flavours more quickly, resulting in a bolder cup.
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Which coffee stood out? When it came to the coffees themselves, Estate delivered the smoothest and most balanced brew of the evening, while The Fields won over most of our guests with its juicy, fruit-forward character. For many of us, naturally processed coffees with juicy, fruit-forward flavours made particularly exciting cold brews, proving just how expressive the method can be.
Overall, the session reminded us that there isn't one perfect cold brew recipe. Every variable, from the coffee itself to the brewing time, ratio and water, helps shape the final cup. The best recipe is the one that suits your taste, so don't be afraid to experiment and discover your own favourite.
The magic of water
The coffee to water ratio in cold brew (and most coffee drinks, for that matter) is usually 1:8, 1:11 and 1:14, which means that the type of water used for making the coffee is really crucial for the final results. Filtered mineralised water can get the best flavours out of your coffee and that’s what we recommend using for your daily brew at home!
How to Make Cold Brew at Home
We want you to be sipping on the best cold brew this summer, so here’s a recipe you can try out at home. We hope this recipe gives you a great starting point. Once you've got the basics down, don't be afraid to tweak it to suit your taste.
The variables you can play around when experimenting with your cold brew.
You’ll need:
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Coffee: 125g coarsely ground coffee (sea salt-like)
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Water: 1 liter of cold, filtered water
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Jug: A large jar, pitcher or a French press
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Filter: A fine mesh sieve, cheesecloth or a nut milk bag.
Instructions:
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Place ground coffee in a jug and pour cold water on top of them.
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Gently stir the coffee to make sure everything is well mixed together.
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Cover the jug with a lid and let it steep in the fridge or room temperature for 12-18 hours.
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Slowly pour the mixture through the chosen filter into a new jug to separate the coffee grounds from the liquid.
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Serve over ice and enjoy!
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Store the remaining cold brew in the fridge for up to 7 days.
Want to make cold brew at home with even less fuss? Hario Mizudashi Cold Brew Maker is designed to make the process simple, helping you brew smooth, refreshing coffee with minimal effort. It's available on our website, alongside the coffees we love brewing with.
