Cold brew uses a very long immersion, so it needs very little help from surface area.
The setting
Coarse — like sea salt, similar to or slightly coarser than French press.
Why coarse
Extraction time is 12 to 18 hours. A medium grind over that period over-extracts substantially, producing bitterness even at fridge temperature.
Filtering. Fine grounds make straining slow and produce a silty, heavy concentrate. Coarse grounds drain freely.
The trade-off if you go too coarse
Weak, watery concentrate. If your cold brew is thin, grind slightly finer or extend the steep, not both.
Fines are the enemy here
A blade grinder produces a huge quantity of fines regardless of setting. In a 16-hour steep those fines over-extract completely and the result is bitter and muddy.
This is one of the methods where a burr grinder matters most, despite cold brew’s reputation for being forgiving.
The ratio
1:8 for a concentrate to be diluted 1:1 or more. 1:15 to drink as is.
The steep
12 to 18 hours in the fridge, or 8 to 12 at room temperature. Room temperature extracts faster — do not do both long and warm.
Straining
Let it drain by gravity. Squeezing or pressing the bag forces out the bitter, silty last fraction.
A paper filter after the first strain gives a much cleaner result.
Last reviewed 8 August 2026