Cold brew is filter coffee's slowest cousin. You drop coffee and cold (or room-temperature) water into a vessel, leave it for 12–24 hours, and then strain. No heat, no pour, no fuss. Time replaces temperature as the extraction lever.
What changes when you remove heat
Heat dissolves the bitter, acidic, and aromatic compounds first; sweetness and body trail behind. Skip the heat and you skip a lot of the bitter. What's left is a lower-acidity, smoother, often chocolate-and-nut-leaning concentrate. Florals and bright acids — the things hot brewing is great at — barely show up. That's why even a complex single-origin can taste muted brewed cold.
For that reason, most people who brew cold regularly use medium and dark roasts and don't reach for their best Ethiopian.
Ratio, time, and what they do
- Ratio: 1:8 to 1:5 (much stronger than hot brew). The output is meant to be diluted — typical serve is 50/50 with water or milk.
- Time: 12–24 hours in the fridge. Shorter (8h) for darker roasts, longer (24h) for lighter or coarser grinds.
- Grind: coarse, like French press. Finer grinds over-extract over so many hours and bring back the bitterness you were avoiding.
How to brew it
Coffee + water in a jar. Stir to wet all the grounds. Cover, refrigerate. Strain through a paper filter (cleanest), a Clever, an AeroPress, or a French press (silty but acceptable).
Don't reuse grounds. Don't squeeze the filter to get the last drops out — that pushes bitter fines straight through. And don't skip the strain: silt left sitting in the concentrate keeps extracting and turns it bitter over the days it's in the fridge.
Water still matters
Cold extraction doesn't make water minerality irrelevant — it makes it slower to show up. The same hard water that tastes flat in a hot brew tastes flat in cold brew, you just notice it later because the dilution masks the first sips. Use the same water you'd use for a V60 (see Water minerality in Techniques). Tap-water cold brew is often the difference between "smooth" and "smooth and dull."
Storage
Concentrate keeps in the fridge 1–2 weeks sealed. Diluted (already mixed with water) keeps 3–4 days. After that the aromas flatten, even if it doesn't go off.
When to use it
Hot weather. Office. Iced drinks. Coffee for people who say they don't like coffee but can be talked into something cold and sweet. It's also the most forgiving introduction to brewing — there's no technique to flub.
