Reference
Brewing
Ratios, temperatures, grind sizes, and a troubleshooting guide that names the actual cause instead of telling you to experiment.
There are four variables that matter: ratio, grind, temperature, and time. Almost every brewing problem is one of them being wrong, and almost every brewing guide tells you to adjust all four at once.
Change one thing at a time. Write down what you changed. That’s the entire method.
Starting points by method
These are places to start, not rules. Once a coffee is dialled in, the numbers for that coffee matter more than the numbers here.
Pour-over (V60, Chemex)
The most controllable method and the most revealing. Nothing hides an imbalance like a pour-over, which is exactly why it’s the best way to evaluate a new coffee. Use the top of the temperature range for light roasts.
French press
Full immersion with a metal filter, so the oils and fine particles stay in the cup. Produces the heaviest body of any common method. Don’t plunge and leave it sitting. Decant immediately or extraction continues.
AeroPress
The most forgiving method here, and the most tolerant of a mediocre grinder. Lower temperatures work well because the short brew time and pressure make up for the reduced extraction.
Espresso
The least forgiving. Everything about the grind matters, and a burr grinder built for espresso is not optional. Judge by taste and time together. A shot that hits the right time but tastes sour is still under-extracted.
Cold brew
Time replaces heat. The low temperature never extracts most of the acidic compounds, which is why cold brew tastes smooth and why it also flattens a delicate coffee. Use something with body and chocolate character, not your best Gesha.
Ratios
Ratio is coffee weight to water weight. Volume measurements are useless because grind size changes how much coffee fits in a scoop. A kitchen scale is the single highest-value piece of equipment you can buy.
| Method | Ratio | 20 g of coffee needs |
|---|---|---|
| Pour-over | 1:16 | 320 g water |
| French press | 1:15 | 300 g water |
| AeroPress | 1:15 | 300 g water |
| Espresso | 1:2 | 40 g liquid out |
| Cold brew concentrate | 1:8 | 160 g water |
Strength and extraction are different things, and confusing them is the most common mistake in home brewing. Ratio changes strength. Grind and time change extraction. A weak-tasting cup might be under-dosed, or it might be under-extracted, and the fix is different in each case.
Grind size
| Grind | Feels like | Use for |
|---|---|---|
| Extra coarse | Peppercorns | Cold brew |
| Coarse | Sea salt | French press, percolator |
| Medium-coarse | Rough sand | Chemex, Clever dripper |
| Medium | Beach sand | Drip machines |
| Medium-fine | Fine sand | V60, AeroPress, siphon |
| Fine | Table salt | Espresso, moka pot |
| Extra fine | Powdered sugar | Turkish |
Grind immediately before brewing. Ground coffee stales in minutes, not days. The increase in surface area is enormous and oxidation runs accordingly.
Water
Coffee is 98% water, and bad water puts a ceiling on everything else.
- Filtered, always. Chlorine is detectable in the cup at concentrations well below what you’d notice drinking the water plain.
- TDS 150–300 ppm. Distilled or reverse-osmosis water is too pure. Minerals participate in extraction, and water with nothing dissolved in it makes flat, hollow coffee.
- pH 6.5–7.5. Hard alkaline water neutralises the acids that make a bright coffee interesting.
Temperature by roast level
| Roast | Temperature | Why |
|---|---|---|
| Light | 96–100 °C | Dense, hard beans need the energy to give anything up |
| Medium | 93–96 °C | The default for most coffee |
| Dark | 88–93 °C | Already fragile from the roast; too much heat extracts ash |
Troubleshooting
The symptom tells you which direction to move. Change one variable, brew again.
Bitter, harsh, drying
Over-extraction. You pulled too much out of the grounds.
- Grind coarser (the first thing to try)
- Lower the water temperature by a few degrees
- Shorten the brew time
- Check the ratio: too much water for the dose reads as bitter, not weak
Sour, sharp, thin
Under-extraction. You didn’t pull enough out.
- Grind finer
- Raise the water temperature
- Extend the brew time
- Agitate more during the bloom
Sour is by far the more common problem, and it’s regularly misdiagnosed as bitter. If a cup is unpleasant in a way you can’t name, try grinding finer first.
Weak but not sour
Under-dosed. Use more coffee, not a finer grind. A finer grind on an already correct extraction pushes you into bitterness.
Muddy or silty
Grind is too fine for the filter, or the filter is failing. Common in French press with a grinder that produces lots of fines. Go coarser and decant off the sludge.
Uneven, tastes different every time
Usually pouring technique or channelling. In a pour-over, water is finding a path through the bed instead of saturating it. Pour in slow concentric circles, keep the bed level, and let the bloom finish before continuing.
Storage
- Airtight and opaque, at room temperature. A one-way valve bag is designed for this and is fine as a storage container.
- Not the fridge. Coffee is porous and hygroscopic; it will absorb moisture and whatever else is in there.
- The freezer works but only for long-term storage of unopened bags, and only if you never thaw and refreeze. Condensation on the beans is the enemy.
How long it stays good
| Age from roast | State |
|---|---|
| 0–3 days | Still degassing; espresso will be unstable |
| 3–14 days | Peak. This is the window |
| 2–4 weeks | Good, gradually flattening |
| 4–6 weeks | Drinkable, noticeably duller |
Whole beans stale far more slowly than ground. If you buy pre-ground coffee, the clock started at the grinder, not at the roaster.
Terms worth knowing
- Bloom. The CO₂ that escapes when hot water first hits fresh grounds, making the bed swell and foam. It’s a freshness indicator: no bloom means old coffee.
- Extraction. The proportion of the ground coffee’s soluble mass that ends up dissolved in the cup. Around 18–22% is the usual target.
- Channelling. Water finding a low-resistance path through the coffee bed and under-extracting everything it bypassed.
- Crema. The emulsified layer on espresso. Indicates freshness and pressure, not quality.
- Cupping. The standardised tasting protocol: coarse grind, hot water, crust broken at four minutes, slurped from a spoon.
- Terroir. The environmental fingerprint of a place: altitude, soil, rainfall, shade.
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