This spring we bottled our first single-origin cold brew. People keep asking what is in it, which is a fair question and has a very short answer.
Coffee and filtered water. That is the list.
No sugar, no dairy, no “natural flavours,” no preservative, no stabiliser, nothing to correct for something else being wrong. There is nowhere to hide in a two-ingredient drink, which is the entire reason we make it that way and also the reason it took as long as it did to get right.
Why cold, and why so long
Heat is a shortcut. Hot water pulls everything out of a coffee in about four minutes — the sugars, the acids, and the bitter compounds that arrive last and that a good barista is racing to leave behind. It is a fast, violent, difficult-to-control extraction, and when it goes well it is glorious.
Cold water cannot do any of that. It is a far weaker solvent, so it takes the sweetness and the soluble sugars and it largely never gets around to the harsh end. What you lose is aromatic sparkle — the floral, tea-like top notes simply do not come across cold. What you gain is body, chocolate, caramel, and an acidity so low that people who have given up on coffee for their stomach can usually drink it.
Twenty-four hours is the number because at eighteen it is thin and at thirty-six it starts to taste of the fridge. We tested a great many batches to arrive at a figure we could have guessed. That is research.
Doing it at home
It is genuinely difficult to get wrong, which is why we are happy to tell you exactly how.
Grind coarse — coarser than you think, coarser than French press, like rough sea salt. Weigh it. Combine with filtered water at 1:8 if you want a concentrate to cut later, or 1:15 to drink as it comes. Stir once so everything is wet. Cover it. Put it in the fridge, not on the counter — this matters, it is a food-safety point as much as a flavour one.
Twenty-four hours later, strain it through a paper filter. Not cheesecloth, which will let the fines through and leave you with something silty. It will keep about a week refrigerated, and it will be noticeably better on day two than on day one.
Over ice, in a glass, in July. There is not much more to it than that, which was always the point.
