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Cold brew is fundamentally a different extraction method, not just iced hot coffee. The absence of heat changes everything: extraction is slower and less complete, acidity is lower, certain bitter compounds dissolve less readily, and the result has a naturally smooth, low-acid character that hot brewing cannot replicate by chilling. Understanding the variables lets you tune cold brew deliberately rather than just following a recipe and hoping for the best.
Heat dramatically accelerates the extraction of almost all 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.
A typical espresso brew ratio is 1:2 (1g coffee to 2g water). A pour-over is around 1:15. Cold brew concentrate is usually 1:4 to 1:6, and ready-to-drink cold brew is 1:7 to 1:10. The higher coffee-to-water ratio compensates for the less efficient extraction at cold temperatures. If you use a hot-coffee ratio for cold brew, the result will be watery and under-extracted. If you are making concentrate for mixing with milk or water, use a tighter ratio (1:4 to 1:5) and dilute to taste. If you are making ready-to-drink cold brew, start around 1:7 and adjust based on strength preference.
Cold brew steeped at refrigerator temperature (4-6 C) takes 12-24 hours for a balanced result, with most recipes landing at 18-20 hours. Room temperature cold brew (18-22 C) extracts faster — 8-12 hours is typically enough — but the result is slightly more acidic and less stable. Fridge-steeped cold brew is the safer default: slower extraction gives you a wider margin for error and a cleaner, rounder result. Beyond 24 hours in the fridge, over-extraction can produce woodiness and bitterness. The coarser the grind, the longer you can steep without over-extracting.
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.
Properly filtered cold brew stored in a sealed container in the refrigerator keeps for 10-14 days with no meaningful quality loss. The low temperature and absence of dissolved oxygen slow degradation significantly compared to hot coffee. Unfilitered cold brew or cold brew with milk added degrades faster — consume within 3-5 days. Concentrate stores slightly better than ready-to-drink cold brew because the lower water content reduces the microbial environment. Do not store cold brew at room temperature for more than a few hours, particularly in warm weather.
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