Espresso Troubleshooting: Fix Sour, Bitter and Fast Shots

To troubleshoot espresso, start with taste, then check shot time. A sour, thin shot that runs in under about 20 seconds is under-extracted: grind finer, or pull a slightly longer shot. A bitter, dry shot that takes more than about 40 seconds is over-extracted: grind coarser, or stop the shot sooner. A shot that tastes both sour and bitter, spurts, or leaves holes in the puck is channeling, which you fix with better puck preparation. If the time is right but the taste is still wrong, look at your beans, water and temperature. Start from a standard recipe of about 18 g of coffee in, 36 g of espresso out (1:2) in 25 to 30 seconds, and change one thing at a time.

Start With a Baseline Recipe

You cannot diagnose a shot without knowing what you put in and got out. Weigh the dry coffee and the espresso on a coffee scale and time every shot; an espresso scale with a built-in timer that fits on the drip tray makes this easy. A good starting point for most beans and machines is:

• Dose: about 18 g of finely ground coffee in a double basket (most double baskets take 16 to 20 g).
• Yield: about 36 g of espresso, a 1:2 ratio.
• Time: about 25 to 30 seconds from pressing the button.
• Temperature and pressure: around 200°F (93°C) and about 9 bar, the default on most machines.

Treat these as a starting point, not a rule. Light roasts often taste better with a longer ratio (1:2.5 or more), dark roasts with a shorter one. See what is espresso and ristretto vs lungo for how ratio changes the drink.

Read the Shot: Taste, Time, Flow and Crema

• Taste is the best clue. Sour, sharp or salty means under-extracted; bitter, dry or ashy means over-extracted; hollow or weak means the shot lacks strength or the beans are past their best.
• Time confirms it: a shot well under 20 seconds is usually under-extracted, one well over 40 seconds usually over-extracted.
• Flow: a good shot starts after a few seconds and runs in a steady, syrupy stream that slowly turns lighter. Gushing means too little resistance; slow dripping means too much.
• Crema: it should be hazel-brown and even. Thin, pale crema suggests under-extraction or stale beans; very dark, patchy crema suggests over-extraction. See what crema tells you.

A bottomless (naked) portafilter, like the one above, shows you exactly how the shot flows. Spurts, pale streaks or a stream that comes from one side are signs of channeling.

Sour Espresso: How to Fix Under-Extraction

Under-extracted espresso tastes sharply sour, like lemon rind or unripe fruit, sometimes salty, with a thin body and a short finish. It is different from the pleasant, juicy acidity of a good light roast: under-extraction tastes sharp and unbalanced rather than bright and sweet. It happens when water passes through the coffee too quickly to dissolve enough of the sugars and other flavors.

1. Grind finer in small steps to slow the shot toward 25 to 30 seconds.
2. Pull a longer shot if the time is already right, for example 18 g in and 40 to 45 g out.
3. Raise the dose slightly, by 0.5 to 1 g, if your basket has room.
4. Check the temperature: water that is too cool also causes sourness, especially with light roasts.

Bitter Espresso: How to Fix Over-Extraction

Over-extracted espresso tastes harsh and bitter at the back of the tongue, often with a drying, astringent feel, like strong black tea. A burnt or ashy taste usually comes from a very dark roast or water that is too hot rather than from the extraction itself. Over-extraction happens when the water stays in contact too long and pulls out the harsh compounds that come after the good ones.

1. Grind coarser one step at a time until the shot runs in about 25 to 30 seconds.
2. Stop the shot sooner, for example at 30 g instead of 36 g.
3. Lower the dose by 0.5 to 1 g if the basket is overfilled and the coffee touches the shower screen.
4. Lower the temperature a little for dark roasts, if your machine allows it.

For the same principles applied to drip and pour-over, see why coffee tastes bitter or sour.

Channeling: Fix Your Puck Prep

Channeling happens when water finds weak spots in the coffee bed and rushes through them, over-extracting those paths while leaving the rest under-extracted. The result tastes sour and bitter at the same time. Signs include spurts from a bottomless portafilter, a stream that turns pale early (blonding), and small holes or cracks in the spent puck. Changing the grind will not fix it; better preparation will:

1. Break up clumps with a WDT tool, a set of fine needles you stir through the grounds. See our guide to WDT tools and techniques.
2. Level the bed before tamping, by tapping the portafilter or using a distribution tool.
3. Tamp level and firm. The exact pressure matters less than tamping the same way, and perfectly flat, every time.
4. Start clean: wipe the basket dry and keep the shower screen and gasket clean; see how to clean an espresso machine.

Good Shot Time but Bad Taste? Check Beans, Water and Temperature

• Bean age: espresso beans usually taste best from about one to four weeks after roasting. Very fresh beans can be gassy and spurty; old beans taste flat and give thin crema. Check the roast date.
• Roast and blend: very light roasts are harder to extract as espresso and may need a finer grind, hotter water and a longer ratio. See espresso blends.
• Water: very hard water dulls flavor and scales up your machine; very soft or distilled water tastes flat and sour. The SCA targets about 150 mg/L (ppm) of total dissolved solids. See the best water for coffee.
• Temperature: most machines brew around 195 to 205°F (90 to 96°C). Too cool tastes sour; too hot tastes bitter or burnt.
• Grinder: an inconsistent or low-quality grinder makes channeling and mixed flavors much more likely. See our best coffee grinders.

Dial In in the Right Order

Change one thing at a time, starting with the easiest:

1. Keep the dose fixed at a sensible amount for your basket.
2. Adjust the grind until the shot runs in about 25 to 30 seconds at a 1:2 ratio.
3. Adjust the ratio by taste: longer for sour shots, shorter for bitter ones.
4. Fix puck prep if you see channeling.
5. Check beans, water and temperature if the time is right but the taste is still wrong.

Write down the dose, yield, time and grind setting for each shot so you can see what changed. Once your shots taste right, see how to drink espresso, or compare machines in our guide to the best home espresso machines.