Make Cold Brew Yourself: Instructions & Ratio

Once temperatures rise, the same question comes up again: How do you actually make really good cold coffee? Cold Brew is the answer that has been sweeping through every café and living room for years. Brewed with cold water, steeped for hours, allegedly easier on the stomach and stronger than anything else. Much of this is true. Some of it is marketing that doesn't hold up under scrutiny.

We'll show you how Cold Brew works, what the science really says about acidity and caffeine, and how to get results with simple equipment that clearly beats store-bought bottles. At the end, there are also twelve recipes from coffee professionals from the German-speaking region.

What is Cold Brew?

Cold Brew is coffee that's extracted with cold water over many hours. It's brewed without hot water and with minimal agitation. The coffee grounds simply sit in cold water for 12 to 24 hours and slowly release their soluble compounds. It's a pure immersion method, similar to the French Press, just cold and much slower.

Two things that are often confused need to be distinguished:

Cold Drip is not the same. Here, cold water drips slowly through a coffee bed instead of the coffee bathing in water. This produces a different, often clearer profile and a more concentrated result, but requires special equipment.

Flash Brew (also called Japanese Iced Coffee) isn't cold brew at all. This is brewed hot over ice, so the coffee is extracted normally with hot water and cooled immediately. This is an important distinction to come back to, because it makes a big difference in taste.

Does cold water really make coffee less acidic?

This is the most persistent promise around Cold Brew. And it's more complicated than you'd think. A well-regarded study from Thomas Jefferson University compared hot and cold brewing of the same coffee side by side. The result: The measured pH value was practically the same for both methods, in the range of about 4.85 to 5.13. So Cold Brew isn't fundamentally low in acid, at least not when it comes to pH.

What the researchers did find: Hot-brewed coffee contains more titratable acids. In other words, there are more acid molecules in play that your tongue perceives, even if the pH is similar. This is exactly where the honest explanation lies. For many people, Cold Brew tastes softer and rounder because certain acids and bitter compounds aren't extracted as well at low temperatures. It's a matter of perceived acidity, not dramatically lower pH.

Flash Iced Coffee filter coffee brewed directly over ice. The ice cubes are counted as a "bypass."

Does Cold Brew have more caffeine?

You hear this all the time too: Cold Brew is a caffeine bomb, two to three times as strong. A 2017 study looked at the influencing factors of time, roast level, and grind size. The short answer: It depends, and the blanket multiple doesn't hold true.

The caffeine content depends heavily on the roast level and grind size, and especially on the ratio in which you brew. Cold Brew is often made as a concentrate, with a lot of coffee and little water. If you drink this concentrate straight, you get accordingly more caffeine. If you dilute it before drinking, which is the norm, that quickly evens out. So the high strength usually comes from the brewing ratio, not from some magical property of cold water.

Antioxidants, the second health aspect often mentioned, behave just as soberly: At light roast, the content is roughly the same in hot and cold brewing; at dark roast, the hot method actually extracts more.

Cold Brew Basic Recipe Step by Step

The great thing about Cold Brew: You don't need special equipment. A French Press works perfectly because it combines the retention vessel and filter in one. Alternatively, a large glass or pitcher and a hand filter for straining.

Cold Brew steeped in the refrigerator for 20 hours.

The Parameters in Detail

Cold Brew forgives a lot, but if you want really good results, you adjust four levers. The most important is grind size: Over the long contact time, it's the biggest factor for strength and clarity. Then come ratio, steep time, and water.

How strong the final drink really is can be classified by dissolved solids. Cold Brew is often higher here than filter coffee, especially as a concentrate. This is precisely why it's usually diluted before drinking.

Since grind size is the central lever, a reference helps. Green marks the right preparations; the bars below show the setting values for our hand grinders. Cold Brew is all the way to the right in the coarse range.

Cold Brew or Flash Iced Coffee Instead?

This is where it gets interesting, and this is where most guides don't dare to go. Cold Brew isn't automatically the best way to make cold coffee. Cold extraction does pull out fewer bitter compounds, but it also gets fewer of the fine, fruity, and floral aromas that make a good specialty coffee worth buying. If you have a light, complex coffee, Cold Brew often wastes exactly what you paid for.

The alternative is called Flash Brew or Japanese Iced Coffee: brewed hot over ice. Hot extraction brings out the full range of flavors, and the ice sets them immediately. The result is clearer, livelier, and fruitier, though not as long-lasting. With Flash Brew, you simply weigh your ice cubes and adjust your brewing amount accordingly: for example, put 150 g ice cubes directly in the pitcher, then brew 150 g water over 30 g coffee with a V60. The important thing is to brew slowly but with plenty of agitation so you achieve high extraction with the little water you have.

Clarity, Filtering, and Shelf Life

How clear your Cold Brew becomes depends on filtration. The metal filter of the French Press lets fine particles through, which gives more body but also a slight cloudiness and dustiness. If you prefer it clearer, pour it additionally through a paper filter.

For shelf life: Cold Brew belongs in the refrigerator. It's usually good for two to three days when handled cleanly. A concentrate can last five to seven days depending on the method. In the end, trust your nose and eyes, not wishful thinking.

Which Coffee is Best for Cold Brew?

Basically, Cold Brew works with almost any coffee, but not every coffee shows itself at its best. Medium roasts with notes of chocolate, nuts, and caramel come across very smooth when cold. Very light, fruity filter coffees often unfold their potential better in Flash Brew. A good, uncomplicated entry point is our Amigo Filter Coffee, which tastes soft and balanced.

Common Mistakes

Ground too fine. The most common mistake. Over hours, fine powder over-extracts, the Cold Brew becomes bitter and cloudy, and is hard to filter. So grind coarsely.

Not enough coffee. Because immersion extraction is inefficient, Cold Brew that's too weakly brewed tastes watery. Better to use a bit more coffee and dilute at the end.

Steeped too long. More than 24 hours brings little gain and more bitterness. Stay within the time window mentioned.

Wrong coffee for the purpose. Cold extracting your expensive, light favorite coffee can be wasteful. For complex coffees, it's worth looking into Flash Brew.

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 the German-speaking region for their favorite recipes: barista champions, Brewers Cup champions, and cup tasting masters. A highlight to taste comes from World Champion Emi Fukahori.

Emi brews on a large scale: 500 g coarsely ground coffee to 5 L of cold water with a hardness around 80 ppm. Put everything in a tank or bucket and let it rest in the refrigerator for 20 hours. Then pour through a coarser pre-filter and then through V60 filter paper until all solid particles are removed. Serve over ice, optionally a chocolatey Pulp Natural from Brazil, a fruity Natural, or a floral, washed coffee. Emi Fukahori is Brewers Cup World Champion and founder of Café Mame in Zurich.