Ground Coffee: : Why Grind Size is so Important.
More orten than not, if you’re having problems with getting your coffee right at home, it can be traced back to a grind size that doesn’t suit the brew method. Here’s a bit about the science and what’s going on in the coffee maker.
1. Extraction 101: Surface Area Meets Contact Time
Coffee flavour comes from combining soluble compounds with water.
Your coffee grind size dictates how much surface area the water can touch.
Finer grind = more surface area = faster extraction.
That’s perfect for espresso, where water is in contact for only 20 to 30 seconds.
Coarser grind = less surface area = slower extraction.
Ideal for French press or cold brew, both of which steep the ground coffee in hot water for minutes or hours.
If the grain size of the ground coffee doesn’t match the time the water spends with the grounds, you won’t get the full, rich extraction you’re looking for.
2. Under‑Extraction (Grind Too Coarse)
Flavour symptoms: sharp acidity, sourness, salty or “hollow” body.
What’s happening: Water dissolves the easiest‑to‑extract acids first, but leaves behind the sweet sugars and the rich rich oils. Youre getting just the building blocks but not the top notes and the finer flavours.
Example: Using French‑press‑coarse grounds in an Aeropress for i minute. The brew finishes before it can pull the balanced sugars and the fine aromatics—result: sour, muddy coffee.
Fix: Go 1–2 clicks finer on your coffee grinder or lengthen the brew time.
3. Over‑Extraction (Grind Too Fine)
Flavour symptoms: bitterness, “dry” finish, ashy or “woody” aftertaste.
What’s happening: Once the sweet spot is passed, the water begins dissolving the bitter polyphenols and plant fibres that are part of every bean. It’s like leaving tea bags to stew for hours until the liquid is inky brown and full of tannins.
Example: Brewing fine ground coffee in a French press for four minutes. Excess surface area plus long contact time = over‑extracted coffe (and sludge in the bottom of your cup from too fine a grind).
Fix: Go coarser, shorten your brewing time, or lower water temperature slightly.
Ground coffee: Which grind for which brewing method?
| Grind Size | Texture Example | Ideal Brew Methods | Brew Time |
|---|---|---|---|
| Extra‑Coarse | Rock salt | Cold brew, cowboy coffee | 12–24 hrs |
| Coarse | Rough sea salt | French press, percolator | 4–5 min |
| Medium‑Coarse | Raw sugar | Chemex, clever dripper | 3½–4½ min |
| Medium | Sand | Auto‑drip machine, pour‑over (V60) | 2½–4 min |
| Medium‑Fine | Table salt | Aeropress (standard recipe), siphon | 2 min |
| Fine | Powdered sugar | Espresso, stovetop moka | 25–35 sec |
| Extra‑Fine | Flour | Turkish cezve/ibrik | 45–60 sec on heat |