As soon as the temperatures rise, the same question comes back around: how do you actually make good cold coffee? Cold brew is the answer that's been making the rounds through cafés and living rooms for years now. Brewed cold, steeped for hours, supposedly gentler on the stomach and stronger than anything else. Much of that holds up. Some of it is marketing that doesn't survive a closer look.
We'll show you how cold brew actually works, what the science really says about acidity and caffeine, and how to get a result with simple equipment that clearly beats the bottled stuff from the shop. At the end, you'll also find twelve recipes from coffee professionals across German-speaking Europe.
What Is Cold Brew?
Cold brew is coffee extracted with cold water over many hours. There's no hot water involved, and very little agitation. The ground coffee simply sits in cold water for 12 to 24 hours, slowly releasing its soluble compounds. It's a pure immersion method, similar to the French press, just cold and a lot slower.
Two things often get mixed up with cold brew and are worth separating out:
Cold drip isn't the same thing. Here, cold water drips slowly through a bed of coffee instead of the coffee sitting submerged in water. That produces a different, often clearer profile and a more concentrated result, but it needs specialised equipment.
Flash brew (also known as Japanese iced coffee) isn't cold brew at all. Here, the coffee is brewed hot over ice, so it's extracted at normal hot-brew temperature and cooled down immediately. That's an important distinction we'll come back to, because it makes a real difference to how the cup tastes.
Does Cold Water Really Make Coffee Less Acidic?
This is the most persistent promise made about cold brew, and it's more complicated than it sounds. A widely cited study from Thomas Jefferson University compared hot and cold brews of the same coffees directly. The result: the measured pH came out practically the same for both methods, somewhere around 4.85 to 5.13. So cold brew isn't inherently low in acid, at least not by pH.
What the researchers did find is that hot-brewed coffee contains more titratable acid. That means more acid molecules are actually present for your tongue to pick up on, even though the pH is similar. That's the honest explanation here. Cold brew tastes softer and rounder to a lot of people because, at lower temperatures, certain acids and bitter compounds simply don't extract as readily. It's a question of perceived acidity, not a dramatically lower pH.
Flash iced coffee, filter coffee brewed directly over ice. The ice cubes are counted as part of the brew water ("bypass").
Does Cold Brew Have More Caffeine?
This is another claim you hear constantly: that cold brew is a caffeine bomb, two to three times stronger than regular coffee. A 2017 study looked at the factors involved: time, roast level and grind size. The short answer: it depends, and that blanket multiplier just doesn't hold up.
Caffeine content depends heavily on roast level and grind size, and above all on the ratio you brew at. Cold brew is often made as a concentrate, with a lot of coffee to very little water. Drink that concentrate straight and you'll get a correspondingly high amount of caffeine. Dilute it before drinking, which is the normal way to do it, and that difference shrinks fast. So the extra strength mostly comes down to the brew ratio, not some magical property of cold water.
Antioxidants, the other health angle people like to bring up, turn out just as unremarkable: with lighter roasts, the levels are about the same whether brewed hot or cold, and with darker roasts, the hot method actually extracts more.
Basic Cold Brew Recipe, Step by Step
The great thing about cold brew: you don't need any special equipment. A French press is all you need, since it's both an immersion vessel and a filter in one. Alternatively, use a large jar or jug and a pour-over dripper to strain it.
Cold brew set up in the fridge for 20 hours.
The Parameters in Detail
Cold brew is fairly forgiving, but if you want a genuinely good result, there are four levers to work with. The most important is grind size: over such a long contact time, it's the biggest factor in strength and clarity. After that come ratio, steep time and the water itself.
| Parameter | Practical value | Effect |
|---|---|---|
| Grind size | Coarse (as for French press) | Biggest lever for clarity and strength, prevents bitterness |
| Ratio | 1:10 to 1:13 ready to drink, from 1:8 as a concentrate | Determines the strength; concentrate is diluted before drinking |
| Steep time | 12–16 h, 24 h maximum | Longer brings barely more extraction, but more bitterness |
| Water | cold, soft | Soft water keeps the coffee clear and balanced |
How strong the finished drink actually is can be gauged by total dissolved solids. Cold brew often comes out higher here than filter coffee, especially as a concentrate. That's exactly why it's usually diluted before drinking.
Since grind size is the key lever here, a reference chart helps. The green bars mark the matching brew methods, and the bars beneath show the setting values for our hand grinders. Cold brew sits right at the far end, in the coarse range.
From extra fine to extra coarse – in micrometres (µm), with the matching brew methods and the setting values for our hand grinders, measured from the zero point. Cold brew sits right at the far end, in the coarse range.
© Kaffeemacher:innen · kaffeemacher.ch · kaffeemacher.de. Grinder values from our own measurements (Comandante) or kaffeemacher.ch (C5); Slim 3 & Kinu approximate micron ranges for orientation.
Cold Brew or Flash Iced Coffee?
This is where it gets interesting, and where most guides don't dare to go. Cold brew isn't automatically the best way to make cold coffee. Cold extraction pulls out fewer bitter compounds, sure, but also fewer of the fine, fruity and floral notes that make a good specialty coffee worth drinking. If you've got a light, complex coffee, cold brew often throws away exactly what you paid for.
The alternative is flash brew, or Japanese iced coffee: hot brewed over ice. Hot extraction brings out the full range of flavours, and the ice locks them in immediately. The result is clearer, livelier and fruitier, though it doesn't keep as long. For flash brew, just weigh your ice cubes and adjust your brew amount accordingly: for example, put 150 g of ice cubes straight into the jug, then brew 150 g of water over 30 g of coffee using a V60. The key is to brew slowly but with plenty of agitation, so you still get a high extraction despite using so little water.
"An interesting middle path: pour one third of the brew water on hot. Then add the remaining two thirds cold, and leave it in the fridge for eight hours afterwards. That brings the two worlds together. We first extract the components that only dissolve with hot water. After that, we deliberately lean on the strength of slow extraction. The result is a more complex coffee that combines acidity, liveliness and the typical deeper, darker notes."
Clarity, Filtering and Shelf Life
How clear your cold brew turns out comes down to filtration. The metal mesh in a French press lets fine particles through, which gives more body, but also a bit of cloudiness and grittiness. If you prefer it clearer, pour it through a paper filter as well.
On shelf life: cold brew belongs in the fridge. Ready-to-drink cold brew is generally fine for two to three days if you've worked cleanly. A concentrate can keep for five to seven days, depending on the method. In the end, trust your nose and your eyes, not wishful thinking.
Which Coffee Works Best for Cold Brew?
In principle, cold brew works with almost any coffee, but not every coffee shows its best side this way. Medium roasts with notes of chocolate, nut and caramel come out really smooth when cold brewed. Very light, fruity filter coffees, on the other hand, often reach their full potential better with flash brew instead. A good, easy starting point is our Amigo filter coffee, which tastes soft and balanced.
Chocolate and caramel, paired with a pleasant, fresh acidity that balances nicely against the coffee's sweetness. Medium to full body, with a long caramel finish.
Common Mistakes
Ground too fine. The most common mistake. Over many hours, fine grounds over-extract, and the cold brew turns bitter and cloudy, and is hard to filter properly. Grind coarse instead.
Not enough coffee. Because immersion extracts inefficiently, a cold brew set up too weak just tastes watery. Better to use a bit more coffee and dilute it at the end instead.
Steeped too long. More than 24 hours brings almost nothing extra, just more bitterness. Stay within the window given above.
The wrong coffee for the job. Cold-brewing your expensive, light-roast favourite can be a waste. For complex coffees, flash brew is worth a look instead.
Twelve Cold Brew Recipes from Coffee Professionals
A good cold brew base already tastes great on its own. But it's also the perfect foundation for summer drinks and cocktails. We asked twelve professionals from German-speaking Europe for their favourite recipes: barista champions, Brewers Cup champions and cup tasting masters. One standout to try comes from world champion Emi Fukahori.
Emi brews on a large scale: 500 g of coarsely ground coffee to 5 litres of cold water with a hardness of around 80 ppm. Everything goes into a tank or bucket and rests in the fridge for 20 hours. It's then poured through a coarser pre-filter and finally through V60 filter paper, until every last solid particle is gone. Serve over ice, using either a chocolatey pulp natural from Brazil, a fruity natural, or a floral washed coffee. Emi Fukahori is a Brewers Cup world champion and founder of Café Mame in Zurich.
From Negroni to tonic to mojito: you'll find the full collection of twelve professional recipes from barista champions and competition winners in our article Cold Brew Recipes: 12 Cocktails & Drinks from the Pros. Every one of them builds on the base you just brewed above.
Verdict
Cold brew is simpler than the marketing suggests, and more honest once you set the myths aside. Less acidic is mostly a question of perception, more caffeine a question of ratio. What actually matters comes down to four things: grind coarse, brew cleanly, stay within the time window, and pick the right coffee. If you've got a light, complex specialty coffee, give flash brew a try instead. For anything chocolatey and round, cold brew is an effortless summer staple. You'll find a coffee to match in our filter coffee range, and once the base is sorted, you can move on to the twelve recipes.
