How to make cold brew at home?

Home cold brew is made by steeping 100 g of coarsely ground coffee in 800 ml to 1 litre of filtered cold water (1:8 to 1:10 ratio), then letting it rest 12 to 18 hours in the fridge before straining. The result is a smooth, low-acid concentrate, typically diluted 50/50 with water or milk at serving.

Cold brew relies on long, low-temperature immersion — usually 4-6 °C in a fridge. The slow kinetics favour cold-soluble compounds (sugars, amino acids, chocolatey and fruity notes) while leaving behind much of the chlorogenic-acid bite and some of the bitter molecules that hot water extracts so readily. That is why cold brew tastes the way it does: pronounced sweetness, very low acidity (pH often around 5.5, compared with 4.8-5.1 for a hot filter), and a rounded body without astringency.

A working recipe starts from a concentrate ratio of 1:8 — 100 g of coffee for 800 ml of water — when you plan to dilute at service, or a ready-to-drink 1:15 to 1:17 if you want to pour straight from the bottle. Grind has to be coarse to very coarse, granulometry similar to sea salt or French press territory (around 900-1100 µm), otherwise fines will pass through filters, clog the paper, and cloud the cup. Use filtered water with moderate mineralisation (TDS target 75-150 mg/L) to avoid any metallic edge. Stir gently to wet every grain, cover, and hold in the fridge between 12 hours (lighter, fruitier profile) and 18 hours (fuller, more chocolatey profile). Beyond 24 hours, bitterness starts to dominate.

Filtering happens in two steps: first a coarse pass through cheesecloth, a French press metal screen, or a nut-milk bag, then a fine pass through a paper filter (V60, Chemex) to clarify. The concentrate keeps hermetically sealed for 7 to 10 days; flavour shifts slightly with oxidation, often gaining roundness on day two. In Brussels, Ghent or Liège, specialty coffee shops will serve it on ice in summer, sometimes with tonic or oat milk — in the same family as Japanese iced coffee, though that method pours hot water directly onto ice and should not be confused with cold brew.

Two classic mistakes: using an espresso or filter grind, which over-extracts tannins in 12 hours and gives a harsh cup; and leaving the brew at room temperature, which accelerates fermentation. Caffeine-wise, a 1:8 concentrate packs roughly twice the caffeine of a standard filter at the same volume, which is exactly why final dilution matters.

Immersion cold brew recipe — key parameters

The Patient Brewer's Reward

Cold brew at home is one of the most accessible specialty coffee projects because it requires no special equipment beyond a large jar, a fine mesh strainer or cheesecloth, and time — and the results, when done correctly, are reliably excellent. The method exploits a fundamental chemistry: cold water dissolves a different subset of coffee's soluble compounds than hot water, specifically favouring the larger sugar and melanoidin molecules responsible for sweetness and body while leaving behind the heat-sensitive acids and volatile aromatics that define hot-brewed coffee's character. The result is a naturally sweet, low-acid coffee concentrate with a smoothness that no hot brewing method can fully replicate — not because cold brew is inherently "better" but because it is chemically different.

The ratios for home cold brew concentrate are typically much higher than for hot coffee: 1:4 to 1:7 coffee to water by weight, producing a concentrate intended for dilution before serving (typically 1:1 with water or milk). A practical starting recipe is 100g of coarsely ground coffee to 600g of cold filtered water, steeped in a jar at room temperature for 12-24 hours (12 hours for a lighter, more nuanced concentrate; 24 hours for a more intense, darker result). After steeping, strain through a fine mesh strainer lined with cheesecloth or a paper filter into a clean jar and refrigerate. The concentrate keeps refrigerated for up to two weeks without significant quality degradation — far longer than hot-brewed coffee remains acceptable.

Practical Recommendations

Grind coarser than you would for French press — almost to the coarseness of granulated sugar — to prevent over-extraction during the long steep. Medium or medium-dark roasts work better for cold brew than very light roasts; the high acid content of light roasts is not fully suppressed by cold extraction and can produce a slightly harsh concentrate. Avoid very dark roasts, which tend toward ashy or bitter concentrates that are harsh even when diluted. Room temperature steeping (18-22 °C) produces a more aromatic concentrate than refrigerator steeping (4-6 °C) because enzymatic and microbial activity is somewhat higher at room temperature — use refrigerator steeping for greater safety margin and a cleaner, milder cup if you have any concern about food safety in warm weather. Serve the diluted cold brew over ice in a tall glass for the most refreshing presentation.