Cold brew fails in one of two ways: too weak and watery, or so strong it tastes like cough syrup. Both are ratio problems, and both are fixable in the first batch.
Two ratios, not one
There is no single cold brew ratio because there are two different products. Concentrate is brewed strong and diluted at serving time. Ready-to-drink is brewed at final strength and served as is.
| Style | Ratio | Coffee per 1 L water | Dilution |
|---|---|---|---|
| Concentrate, strong | 1:5 | 200 g | 1:2 water to concentrate |
| Concentrate, standard | 1:8 | 125 g | 1:1 |
| Ready to drink, strong | 1:12 | 83 g | None |
| Ready to drink, standard | 1:15 | 67 g | None |
Grind: coarse, and coarser than you think
Cold brew wants coarse grind, similar to raw sugar or sea salt. Medium grind produces mud that is hard to filter and tastes chalky. If your batch clouds the filter and refuses to drain, it is too fine.
A cheap blade grinder cannot make coarse grind consistently, which is why cold brew is one of the few methods where a burr grinder is not optional if you want repeatable results.
Time and temperature
| Where | Time | Result |
|---|---|---|
| Room temperature | 12 - 14 h | Bright, faster extraction |
| Room temperature | 16 - 18 h | Standard, balanced |
| Fridge | 18 - 24 h | Smoother, less acidity |
| Fridge | 24 h+ | Flat, woody, avoid |
Cold water extracts slowly and mostly pulls sugars and acids, leaving behind the harsh compounds that hot water releases late in a brew. That is why cold brew tastes smoother than the same beans brewed hot and chilled.
How to filter
Filter twice. Once through a metal sieve to remove grounds, then through a paper filter or cloth bag. The second pass is what gives a clean cup, and skipping it is why home cold brew tastes gritty.
Never squeeze the filter bag. It releases fine particles and bitterness, which defeats the point of the slow steep.
Nitro and milk versions
Nitro cold brew is the same concentrate pushed through nitrogen, which gives a creamy texture without dairy. For milk drinks, brew at 1:5 and dilute with milk instead of water, which gives a stronger base against the fat.
A first batch that works
125 g coarse coffee, 1 L cold water, stir once, cover, 16 hours at room temperature, strain twice. Taste it straight, then dilute 1:1. Adjust the next batch by 20 g of coffee at a time and write down what you changed.