How to Make Cold Brew: Ratio, Time and Storage

What makes cold brew different

Cold brew is coffee made without hot water: coarsely ground beans soak in cold or room-temperature water for many hours. Because cold water pulls flavor out very slowly, the process takes half a day or more instead of the few minutes a pour-over needs. In exchange, fewer of the sharp acids and bitter compounds that hot water extracts end up in the cup, so the result tends to taste smooth and rounded. It holds up well as an iced drink, and a single batch of concentrate can last you several days. Coffee made by dripping cold water slowly through grounds, sometimes called Dutch coffee or slow drip, uses different gear and tastes a little different. This guide covers the simplest home method: steeping.

Equipment and beans

You do not need special gear. A lidded glass jar or pitcher, a mesh strainer, paper filters and a kitchen scale are enough. Medium to dark roasts give a comfortable chocolatey, nutty cup, while light roasts keep a gentle fruity acidity and taste brighter. Either way, aroma can fade over the long steep, so beans that were not roasted too long ago work best.

• A lidded glass jar or pitcher made of something that does not hold odors
• A mesh strainer and paper filters: the first catches large grounds, the second the fine ones
• A kitchen scale to weigh both coffee and water
• Coarsely ground beans; without a grinder, ask the shop to grind them coarse

Ratio and grind size

At home it is easiest to make a strong concentrate that you dilute when you drink it. About 1 part coffee to 8 to 10 parts water by weight is a common starting point, so 100 grams of coffee goes with roughly 800 grams to 1 kilogram of water. You can add much more water to make it ready to drink straight away, but a concentrate lets you choose the strength each time and is more forgiving. Grind coarse, like kosher salt or rough breadcrumbs. Ground too fine, the coffee turns muddy and bitter, and the fines clog the filter so straining takes ages.

Step by step

There are only three stages: mix, wait and strain. Keep the timing the same for a few batches and you will quickly find the combination you like.

• Put the coarse grounds into a clean, fully dried jar
• Pour in cold filtered water and stir until no dry clumps remain
• Close the lid and steep in the fridge for about 12 to 24 hours
• Strain out the large grounds with a mesh strainer, then pass it through a paper filter
• Pour the concentrate into a clean bottle, seal it and refrigerate right away

Steeping time and temperature

Too short a steep tastes thin with a pronounced sourness; too long brings woody or astringent notes. In the fridge, around 12 hours tends to give a light, fresh cup, while 18 to 24 hours tends toward strong and heavy. Try about 16 hours first, taste, and adjust next time. Steeping at room temperature is faster, but leaving water and coffee grounds out for many hours is not ideal for food safety, so at home it is safer to steep in the fridge from the start. That goes double in hot weather.

Diluting and serving

The concentrate is far too strong to drink as is, so dilute it with water or milk. Mixing concentrate and water between 1 to 1 and 1 to 2 is a common starting point, and remember that melting ice will thin it further. Add milk for a smooth, nutty cold brew latte. If you want it hot, top the concentrate up with hot water; it will still taste milder than coffee brewed hot from the start. The biggest advantage of a concentrate is that one bottle covers both the days you want it strong and the days you want it light.

Common mistakes

The most common mistake is grinding too fine. Besides the muddy taste, the filter clogs, straining drags on and the coffee sits exposed to air the whole time. Avoid leaving the grounds in the jar for days after steeping, because bitterness and off flavors keep seeping out. Packing the grounds down so water cannot reach them evenly, using a plastic container that holds old smells, and closing the lid loosely so fridge odors get in all spoil the taste too. Many people also try the concentrate neat, find it harsh and give up; remember it is made to be diluted.

Storage and caffeine

Keep strained concentrate in a sealed container in the fridge and drink it within a few days, while it tastes best. Over time it loses aroma and turns sour or flat, and if it smells off or something is floating on top, throw it out. Wash the jar and tools after every batch and let them dry completely. Because cold brew tastes mild, people often assume it has little caffeine, but a concentrate uses a lot of coffee and, depending on how you dilute it, can contain more caffeine than a regular cup. If you are sensitive to caffeine, pregnant or being treated for a medical condition, ask a doctor or pharmacist how much is right for you, and in the evening dilute it more or make it with decaf beans.