COLDBREW SNOB Good coffee. No compromise.

Brewing guide · 抽出

Best Grind Size for Cold Brew

Coarse. Sea salt, not sand. Here's why, and what to do if pre-ground is all you have.

Grind size questions have a short answer in cold brew: coarse — the texture of coarse sea salt or raw sugar. The long answer explains the three problems a fine grind causes, and why every one of them gets worse the longer you steep.

Why coarse wins

Sediment. Fine particles slip through mesh strainers and turn the bottom third of your glass into silt. A coarse grind plus a paper filter produces the clean, tea-clear cup that makes cold brew worth the wait — the full method strains twice for exactly this reason.

Over-extraction. Extraction speed scales with surface area. Over a 16-hour steep, fine grounds have time to give up everything, including the woody, tannic compounds a coarse grind never releases. Fine-ground cold brew is how you make something that manages to be both harsh and muddy.

Filter clogging. Fines pack into a paste that laughs at your strainer. If your last batch took twenty minutes to filter, your grind was the problem, not your filter.

Can you use regular pre-ground coffee?

Yes — with adjustments. Standard grocery pre-ground is a medium grind aimed at drip machines, which means more surface area than cold brew wants. Compensate by:

  1. Shortening the steep to the low end — 12–14 hours, or fridge-steep for extra forgiveness (steep time guide).
  2. Committing to the paper filter. Non-negotiable here; the mesh-only shortcut produces sludge.
  3. Expecting a slightly darker, blunter cup. Still good. Just not the clean version.

What you shouldn't do is buy espresso grind for cold brew. That's not an adjustment situation; that's a new bag.

Burr vs blade

A blade grinder produces boulders and dust in the same batch — the boulders under-extract, the dust over-extracts and clogs, and the result argues with itself. A burr grinder produces uniform particles, and uniformity matters more at coarse settings, not less.

The honest hierarchy for cold brew:

  1. Any burr grinder on its coarsest settings — hand grinders included; a good hand burr costs less than three grocery-store bottles of cold brew and travels. (Ours is on the gear page.)
  2. Grocery store grinder set to "coarse/French press" — free, uniform enough, grind at purchase.
  3. Pre-ground with the adjustments above — fine, we've all been there.
  4. Blade grinder — pulse in short bursts, shake between pulses, accept imperfection.

The setting, in practice

Every grinder numbers its dial differently, so aim by texture: pinch some grounds — they should feel like coarse sea salt and not leave powder on your fingers. On most burr grinders that's the French-press setting or one step coarser. Dial in once, write the number down, and stop thinking about it — the ratio deserves your attention more.