Cold Brew Concentrate

Combine the coarsely ground coffee and cold filtered water in a large mason jar, French press, or dedicated cold-brew vessel. The grind must be coarse — similar to raw sugar or coarse sea salt. Fine grinds over-extract during the long steep and produce bitterness. Stir the grounds and water together to ensure all grounds are saturated with no dry pockets floating on top. Cover the vessel and place it in the refrigerator (4 C / 40 F). Steep for a minimum of 12 hours and a maximum of 16 hours — going beyond 16 hours begins to extract astringent and bitter compounds even in cold water. 14 hours is the sweet spot for most coffees.

Pour the steeped grounds through a fine-mesh strainer lined with a paper coffee filter (or a clean muslin cloth) into a clean jar or bottle. Do not press or squeeze the grounds — gravity is sufficient. Pressing extracts bitter oils and fine particles that cloud and sharpen the concentrate. The filtration will take 5–10 minutes; patience here is rewarded. Once filtered, seal the jar and refrigerate. The concentrate keeps well for up to 2 weeks refrigerated. To serve, dilute 1:1 with cold water or milk for a standard strength, or 1:2 for something gentler.