Cold brew is made with cold water and many hours, not with ice over hot coffee. The result is sweet, low in acidity and very refreshing.
It’s the easiest way to have coffee ready in the fridge all week, and you don’t need any special equipment to make it. A large jar, a strainer, a paper filter and a little patience are enough.
What it is and what it isn’t
Cold brew is not the same as iced coffee. With iced coffee you make a hot drink and chill it all at once; with cold brew the coffee is never heated. Cold water extracts more slowly and leaves behind a good part of the acidic and bitter compounds, which is why the result is so smooth.
Another advantage is that it’s very forgiving. You don’t have to control the water temperature or time it to the second, and an hour more or less barely shows. It’s a good method for when you don’t feel like keeping an eye on the brewer.
The immersion method we use here is a close cousin of the French press: all the coffee in contact with all the water, just at a different temperature and for many hours instead of four minutes. If you already make coffee in a press, you can use it for this too.
Ratio and time
Ratio
For a concentrate, use one part coffee to eight parts water: 100 g of coffee with a very coarse grind for 800 ml of water.
That concentrate isn’t meant to be drunk as is. When serving, dilute it with the same amount of water or milk, or a little more, depending on how strong you like it. If you’d rather make it ready to drink, use one part coffee to fifteen parts water and let it steep a few hours longer.
Time
Between 12 and 18 hours in the fridge. Less than 12 comes out weak; more than 20 starts to turn bitter.
Temperature changes the timing. At room temperature extraction is faster and ten or twelve hours can be enough, but in summer it’s better to do it in the fridge so the coffee doesn’t pick up odd flavors. Write down how long you left it and adjust in the next batch. If your fridge is very cold, extraction slows down and you may need the full eighteen hours.
Which coffee to use
It works better with a medium roast, with chocolate and nutty notes, than with a very acidic light roast.
Use filtered water: in the cold, limescale and chlorine show more than in hot coffee. Since the water spends so many hours with the coffee, any flavor it brings ends up in the bottle.
Buy whole beans and grind them yourself. With the amount of coffee each batch takes, a grind that’s a few days old shows in the result much more than in a single hot cup.
If you feel like something different, try natural-process Ethiopian coffees: cold, they bring out very pleasant strawberry and blueberry notes. A floral washed coffee, on the other hand, can come out too light and does better in the V60.
Step by step
- Grind the coffee very coarse right before you start.
- Mix it with the cold water in a jar and stir so no dry clumps are left.
- Cover it and let it steep in the fridge for 12 to 18 hours.
- Filter it twice, first with a strainer and then with paper.
- Bottle the concentrate and dilute it when serving.
Filtering
Pour it first through a fine strainer and then through a paper filter. That second step removes the sediment and makes it last longer.
Common mistakes
- Grinding fine: the sediment gets through the filter and the drink turns cloudy and bitter.
- Leaving it for more than a day: woody, dry notes appear.
- Not stirring at the start: pockets of dry coffee are left that never extract.
- Storing it unfiltered: the sediment keeps extracting inside the bottle.
Storage
The concentrate keeps for about seven days in the fridge, in a closed bottle. The same storage rules for the beans apply to the drink.
Keep it in a tightly closed glass bottle and away from strong-smelling food. If you notice a vinegary or flat taste, it’s past its best. Make as much as you’ll drink in a week and no more.
Ways to serve it
On its own over ice, with cold milk, or with sparkling water and a strip of orange peel. It also works as a base for desserts, like a granita. Since it has no marked acidity, it pairs well with plant-based milks, which sometimes curdle with a hot, acidic coffee.
If you want it sweeter, add the sugar or syrup to the concentrate before diluting it and stir well, because sugar takes a long time to dissolve in the cold.