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    by Loom Coffee Co. 3 min read

    For cold brew concentrate, start with 454g coffee and 3,785g water, about 1:8.3 by weight. Steep in the refrigerator for 18-24 hours, filter, and dilute to taste; equal parts concentrate and water is a starting point.

    Cold water extracts coffee more slowly than hot water and produces a different balance of flavor. Chocolate-forward coffees are a useful starting point if you want a rounder cup, but washed coffees and lighter roasts can work too. Choose by the flavor you enjoy, then adjust strength and steep time.

    What do you need?

    • Large jar, pitcher, or French press carafe
    • Fine mesh strainer
    • Paper filter or cheesecloth (for second filtration)
    • Burr grinder
    • Kitchen scale (grams)
    • Kettle (for optional hot bloom)
    • 1 lb (454g) coffee, 1 gallon (3,785g) filtered water (for concentrate)

    What ratio and grind size should you start with?

    For concentrate, use about 1:8.3 by weight: 454g coffee to 3,785g water, or one pound per US gallon. After filtering, try equal parts concentrate and water. Adjust the dilution before changing the next batch's recipe.

    Batch size Coffee Water
    Full batch 454g (1 lb) 3,785g (1 gallon)
    Half batch 227g ~1,890g
    Small batch 113g ~945g
    Ready-to-drink 75g 1,200g (1:16 ratio)

    Grind the same as French press: coarse, like kosher salt. Coarser grounds are easier to filter. Finer grounds extract faster and may need less time; they don't automatically produce a harsher cup.

    How long should you steep?

    Steep in the refrigerator for 18-24 hours for concentrate, or 14-16 hours for ready-to-drink. These are starting times. The coffee, grind, and refrigerator temperature affect the result:

    12 hours Early tasting point; the cup may still seem light
    14-16 hours Starting range for ready-to-drink
    18-24 hours Starting range for concentrate
    Past 24 hours Compare before extending; flavor varies by recipe

    Always steep in the refrigerator. Use clean equipment, cover the brew, and keep it cold. Refrigeration slows microbial growth; it doesn't sterilize the coffee or establish a guaranteed shelf life (BCCDC).

    Optional variation: a hot bloom

    To compare hot and cold extraction, make one batch with a short hot-water bloom and another with cold water only. Keep the total water weight and coffee dose the same.

    For the full batch, use 500g of the total water at 94°C / 202°F to wet the grounds. Stir, wait ninety seconds, then add the remaining cold water. Cool the mixture promptly and refrigerate. This changes the extraction profile; judge the result by comparison rather than expecting a guaranteed increase in sweetness.

    Use about 13% of the total water for the hot bloom. For the half batch, use about 250g hot water; for the small batch, about 125g. Subtract that amount from the cold water so the final ratio stays the same.

    Taste both batches at the same dilution. Record which has the acidity, aroma, and body you prefer.

    Which coffees should you use?

    A starting point for a rounder cup

    Chocolate-forward coffees roasted medium or darker are worth trying if you want cocoa, nut, or dried-fruit character. We often suggest Paubrasil Natural for that flavor direction. Tasting descriptors describe our observations, so use them to guide your choice.

    For a brighter iced cup

    Try a washed coffee or a lighter roast, then compare cold brewing with brewing hot over ice. The two methods can emphasize different parts of the same coffee.

    What should you adjust when the cup tastes off?

    Troubleshooting: taste adjustments
    • Thin and underdeveloped: Steep longer (add 2 hours). Or tighten your ratio slightly.
    • Bitter and harsh: Try a shorter steep next time, then compare at the same dilution. There isn't a universal bitterness threshold at twenty-four hours.
    • Silty or chalky: Let sediment settle and filter through mesh followed by paper. If filtration remains difficult, try a coarser grind.

    Recipe: Cold Brew Concentrate

    • Coffee: 1 lb (454g)
    • Water: 1 gallon (3,785g) filtered
    • Ratio: About 1:8.3 by weight (1 lb per US gallon)
    • Grind: Coarse (kosher salt, same as French press)
    • Method: Combine, stir to saturate, cover, refrigerate
    • Optional bloom: 500g of the total water at 94°C / 202°F for ninety seconds; add remaining cold water and cool promptly
    • Steep: 18-24 hours in the fridge
    • Strain: Fine mesh, then paper filter
    • Dilute: 1:1 with water, splash of cream if desired
    • Storage: Keep covered and refrigerated. Make small batches for prompt use; this home recipe has no validated 7-10-day shelf life.

    Works Cited

    Gagné, Jonathan. The Physics of Filter Coffee. Scott Rao, 2021. Chapters 1-2, especially secs. 1.5 and 2.2-2.4.

    Folmer, Britta, editor. The Craft and Science of Coffee. Academic Press, 2017. Chapters on freshness, extraction, and water, including p. 416.

    British Columbia Centre for Disease Control. “Nitro Cold Brew Coffee: Food Safety Risks.” 2018. Used for contamination and validation cautions, not a validated shelf life for this home recipe. Read source.

    For the concentrate recipe, use 454g coffee and 3,785g water, about 1:8.3 by weight. After filtering, try diluting it with an equal amount of water. The ready-to-drink starting recipe uses 75g coffee and 1,200g water, or 1:16, and is tasted without automatic dilution.

    Start with 18-24 hours refrigerated for the concentrate or 14-16 hours for the ready-to-drink recipe. Grind, coffee, temperature, and strength affect the result. There isn't a universal point after twenty-four hours when bitterness becomes inevitable.

    This recipe uses refrigerator steeping with clean equipment and a covered container. Refrigeration slows microbial growth; it doesn't sterilize cold brew or establish a guaranteed storage life. Make small batches for prompt use and keep the filtered coffee cold.

    A coarse grind is a useful cold brew starting point because it's easier to filter. Finer grounds can extract faster and may need a shorter steep. If the brew is silty, try mesh followed by paper filtration and compare a coarser grind next time.

    Chocolate-forward medium roasts are a useful starting point for a rounder cold brew; Loom Coffee Co. often suggests Paubrasil Natural for that direction. Washed coffees and lighter roasts can work too. Compare cold extraction with hot brewing over ice if you'd like a brighter iced cup.

    For the full concentrate batch, use 500g of the total water at 94°C (202°F), stir, and wait ninety seconds. Add the remaining cold water, cool promptly, and refrigerate. Keep the total ratio unchanged and compare with a cold-only batch; the result isn't a guaranteed sweetness improvement.