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Cold brew steeps grounds in cold water over several hours. Grind, coffee-to-water ratio, steep time and dilution all affect the finished drink. Keep preparation and storage refrigerated, as described in the recipe.
Heat speeds up the extraction of many coffee compounds. Cold water extracts much more selectively — organic acids (which create brightness) and certain bitter chlorogenic acids dissolve less readily in cold water than in hot. The result is lower acidity and lower perceived bitterness compared to a hot-brewed coffee made from the same beans. Caffeine still extracts well in cold water, which is why cold brew concentrate can be surprisingly strong. The extended steep time partially compensates for the absence of heat, but some compounds never fully extract at cold temperatures regardless of how long you steep.
Immersion cold brew — the most common home method — involves steeping coarsely ground coffee in cold water for an extended period, then filtering. The grounds remain in contact with water throughout the steep, and extraction continues until you strain. Drip cold brew (also called slow drip or Kyoto drip) uses a tower to drip cold water slowly through a bed of coffee, one drop at a time over several hours. Drip cold brew produces a brighter, more complex cup because the water is always moving through fresh coffee and extracting more selectively. Immersion is simpler and more forgiving; drip produces a more nuanced result but requires specialist equipment.
For cold brew, ratios describe dry coffee to water added. Start with 75 g coffee and 750 g water for a 1:10 brew, or 100 g coffee and 500 g water for a 1:5 concentrate to dilute before drinking. These are starting points, not fixed definitions. Taste and adjust strength with water or milk at serving. Espresso uses a different convention: 18 g dry coffee to 36 g beverage is a 1:2 dose-to-yield ratio.
Use clean equipment and drinking water. For these recipes, steep covered in the refrigerator at 4°C or below for 12–24 hours, then filter into a clean container. Adjust grind and steep time to taste while maintaining refrigeration. Cold extraction is not a heat treatment and should not be treated as a way to sanitise ingredients.
Cold brew uses a much coarser grind than any hot method — coarser than French press, roughly the texture of raw sugar. Fine grounds over-extract in the long steep and produce harsh, bitter cold brew. They also make filtering extremely difficult: a coarse grind filters quickly through a fine mesh or paper, while a fine grind clogs and is almost impossible to strain cleanly. Filter the finished cold brew through a paper filter or a fine mesh strainer lined with a paper coffee filter. Unfiltered cold brew retains oils and sediment that give a heavier mouthfeel but reduce shelf life.
Keep homemade cold brew covered and refrigerated at 4°C or below. Make small batches for prompt use and add milk only when serving. A recipe alone cannot establish a safe shelf life: hygiene, ingredients, packaging and temperature all matter. Do not assume that filtration or a concentrated recipe makes coffee shelf-stable. Follow the storage label for commercially prepared products; their validated processes do not establish the storage life of a homemade batch.
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