What grind size, roast level, and water profile work best for cold brew, and how do I troubleshoot common off-flavors?
Start with a medium-coarse grind (similar to coarse sea salt or French press), a medium-dark roast (Colombian, Guatemalan, or Brazilian for low acidity), and filtered water at 50–150 ppm TDS with neutral pH. This combination balances surface area and flow so the 12–24 h steep extracts sugars and aromatics without over-pulling woody tannins.
#Quick troubleshooting table
| Symptom | Likely cause | Fix |
|---|---|---|
| Gritty, astringent finish | Grind too fine | Coarsen 2–3 clicks on burr grinder |
| Hollow, sour, under-extracted | Grind too coarse or steep < 10 h | Finen grind slightly or extend to 14–16 h |
| Flat, baked flavor | Roast too dark / stale beans | Use beans roasted 7–21 days ago, medium-dark |
| Metallic/mineral aftertaste | Hard water (> 200 ppm) | Dilute tap 1:1 with distilled or use bottled spring |
| Cloudy, muddy cup | Skipped secondary filtration | Pass through paper filter or 0.2 µm syringe filter after cloth |
#Step-by-step baseline recipe
- Weigh 80 g coffee, grind medium-coarse.
- Add 1000 g filtered water (1:12.5 ratio) to a clean 1.5 L jar.
- Stir once gently — no vortex — to wet all grounds.
- Seal, refrigerate at 4 °C for 14 hours (adjust ±2 h to taste).
- Filter through metal mesh, then a rinsed paper filter.
- Store concentrate ≤ 7 days at 4 °C; dilute 1:1 to 1:3 to serve.
Pro tip: For repeatability, log grind setting, water TDS, steep time, and cup score in a spreadsheet — small changes (±1 h, ±1 grind click) shift the chocolate-to-fruit balance noticeably.