Cold brew: time replaces temperature

Every extraction is a trade between heat and time. Chemistry runs slower in cold water — as a rough rule, reaction and dissolution rates fall by about half for every 10 °C you drop — so what a pour-over does in three minutes at 93 °C, room-temperature water needs half a day to approach. Cold brew is that trade taken to its calm extreme: coarse coffee, cool water, 12 to 24 hours of patience.

But cold brew is not slow hot coffee. Solubility itself changes with temperature, and unevenly: many of the acids and delicate aromatics that define a bright pour-over barely dissolve in cold water at all. What does dissolve — sugars, chocolatey and nutty compounds, caffeine — builds a cup with a different shape: heavy, sweet, round, and famously low in acidity.