Cold brew steeps for 12-24 hours, making grind size critical to preventing over-extraction during that long contact time. A coarse grind exposes less surface area, which keeps extraction slow and controlled even over many hours — producing the signature smooth, sweet, low-acid concentrate.

Using a finer grind is the most common cold brew mistake. With 12+ hours of steeping, fine grounds over-extract dramatically, creating a harsh, astringent, and unpleasantly bitter concentrate that no amount of dilution can fix. Fine particles also make straining a nightmare, passing through filters and leaving chalky sediment.

Grind as coarse as you can — think raw sugar or breadcrumbs. This ensures gentle, even extraction over the long steep, resulting in a clean, naturally sweet concentrate. You can always steep longer for more strength, but you cannot undo the bitterness from grounds that were too fine.