Home / Guides / Troubleshooting
Troubleshooting
Dialing in: fix sour or bitter coffee
Sour means under-extracted and bitter means over-extracted. Here's how to tell which you have, and which single change fixes it.
Some links below are affiliate links. If you buy through them we may earn a commission at no extra cost to you. How this works.
Short answer
Sour, sharp or thin means under-extracted: grind finer, use hotter water or brew longer. Bitter, dry or harsh means over-extracted: grind coarser, use slightly cooler water or brew for less time. Change one thing at a time, and start with the grind.
"Dialing in" is barista shorthand for adjusting a recipe until a coffee tastes right. Cafés do it every time they open a new bag. At home it sounds intimidating, but it comes down to one idea: extraction, meaning how much of the coffee's flavor the water dissolves. Too little and the cup is sour. Too much and it's bitter. Nearly every adjustment you can make moves extraction up or down.
Step 1: name the problem correctly
People often confuse sour with bitter, and the fixes are opposite, so it's worth being precise.
| You taste… | It's probably… | Direction |
|---|---|---|
| Sour, sharp, salty, like biting a lemon; thin body; flavor vanishes quickly | Under-extracted | Extract more |
| Bitter, dry and chalky on the tongue (astringent), hollow, harsh aftertaste | Over-extracted | Extract less |
| Balanced but watery or too intense | A strength problem, not extraction | Change the ratio |
| Bitter and sour at the same time, muddy | Uneven extraction | Fix the grinder or technique |
A useful test: pleasant, juicy acidity is good. The mouth-watering brightness of an apple is a feature of many great coffees. Sourness that makes you wince isn't. Similarly, a little bitterness, like dark chocolate, is normal. A drying, chalky feeling on your tongue, like over-steeped tea, is over-extraction.
Step 2: change the grind first
Grind size is the most powerful adjustment, and it's the one baristas reach for first.
- Sour? Grind finer. Smaller particles expose more surface and slow the water down, so both effects increase extraction.
- Bitter? Grind coarser.
Move in small steps: one or two clicks on a hand grinder, or one number on most electric grinders. Keep everything else the same, brew again and taste. Keeping a note on your phone ("Colombia, 15 g, 250 g, 12 clicks, 3:05, slightly sour") speeds this up a lot.
Step 3: check your brew time
Time is both a variable and a diagnostic. In drip and pour-over, the grind controls the time, so a brew that finishes much faster than the recipe says is a strong sign you're grinding too coarse. Typical targets:
- V60 single cup: about 2:45–3:30
- Chemex, 3–4 cups: about 4:00–4:30
- AeroPress: 1:30–2:30 before pressing
- French press: 4:00 steep
- Espresso: roughly 25–32 seconds for a 1:2 shot
In immersion brewers like the French press or AeroPress, time is set separately. Steeping a bit longer extracts more, and a bit shorter extracts less.
Step 4: water temperature
Hotter water extracts faster. Most filter recipes use 90–96 °C (194–205 °F); the SCA's brewing standard centers on about 93 °C.
- Light roasts are dense and hard to extract. They often taste sour at lower temperatures, so try water right off the boil.
- Dark roasts are more porous and extract easily. If they taste harsh, drop to 85–90 °C.
No thermometer? Water just off the boil is close to the top of that range, and it cools as it sits. A cheap thermometer or a variable-temperature kettle removes the guesswork.
Step 5: ratio, for strength rather than flavor balance
If the coffee tastes balanced but too weak or too strong, don't touch the grind. Change the ratio of coffee to water. A good default for filter coffee is 1:16, which is 16 g of water for every 1 g of coffee. Use 1:15 for a stronger cup and 1:17 for a lighter one. The ratio changes strength far more than it changes sourness or bitterness. See coffee-to-water ratios explained or use the calculator.
When nothing works
If you taste bitter and sour at once, or you can't get rid of a problem however you adjust, the cause is usually one of these:
- Blade grinder or an inconsistent burr grinder. A mix of powder and chunks over- and under-extracts at the same time, and no recipe change can fix both. This is the most common cause. See burr vs blade.
- Stale beans. Beans well past their roast date taste flat and papery, which is easy to mistake for sourness or bitterness.
- Channeling in pour-over or espresso. Water finds a fast path through the bed and skips most of the coffee. Pour gently and evenly, and keep the bed level.
- Water. Very soft or distilled water tastes flat. Very hard water mutes flavor and scales your kettle. Filtered tap water is a good middle ground for most people.
- Dirty equipment. Old coffee oils turn rancid and add bitterness. Clean and descale kettles and machines regularly, as the manufacturer recommends.
A 5-minute dialing-in routine
- Brew your usual recipe and note grind, dose, water, temperature and time.
- Taste as the cup cools a little, since flaws show more clearly when coffee isn't piping hot.
- Sour: go one step finer. Bitter: one step coarser. Balanced but weak or strong: adjust the ratio.
- Brew again with only that change.
- Repeat until you like it, then write the settings on the bag.
Most bags take two or three brews to dial in. After that, you'll just be enjoying the coffee.