How to Fix Under Extracted Espresso

As a coffee enthusiast, there’s nothing more frustrating than pulling an espresso shot that turns out under-extracted. It’s the kind of shot that tastes sour, thin, and lacks the depth of flavors you expect from a well-brewed espresso. If you've faced this disappointment, don't worry—I've been there too, and I'm here to guide you through how to fix it. After countless trial runs and experimenting with my espresso machine, here's everything I’ve learned.

What is Under-Extraction?

Before tackling the solution, it’s crucial to understand what under-extraction means and why it happens. Under-extraction occurs when the water passes through the coffee grounds too quickly, not allowing enough time to draw out the coffee’s soluble flavors. As a result, the espresso ends up tasting weak, sour, and acidic. On the other hand, over-extraction results in a bitter, overly strong shot. Achieving the right balance is key.

Signs of under-extracted espresso include:

Sour or sharp acidity: A telltale sign of under-extraction, where the sourness is more harsh than refreshing.
Thin body: A well-extracted espresso should have a rich, thick texture. If yours feels watery and lacks depth, it’s likely under-extracted.
Pale crema: A properly extracted espresso has a thick, golden-brown crema. Pale and thin crema usually signals under-extraction.

Now that we know the problem, let’s explore how to fix it by tweaking a few key variables.

1. Adjust the Grind Size

Grind size is one of the most critical factors affecting espresso extraction. Espresso requires a fine grind, and if the coffee grounds are too coarse, water will flow through too quickly, leading to under-extraction.

When I first started making espresso, I didn’t fully appreciate the impact a small change in grind size could have. If your espresso tastes sour or thin, the first adjustment to make is grinding your coffee finer. A finer grind increases the surface area, allowing the water to extract more flavors from the coffee. However, be careful not to grind too fine, as this can lead to over-extraction.

Tip: Make small, incremental changes to the grind size and test each shot. You’ll begin to notice a difference as the grind approaches the sweet spot.

2. Adjust Your Brew Ratio

Another key factor in fixing under-extracted espresso is the brew ratio—the amount of coffee grounds to water. A typical espresso ratio is 1:2, meaning 18 grams of coffee grounds should yield around 36 grams of espresso. If your shot is under-extracted, you might be using too little coffee or too much water.

Start by experimenting with your dose (the amount of coffee grounds). Try increasing the dose slightly, giving the water more coffee to extract flavor from. Alternatively, reduce the yield (the amount of espresso produced) for a more concentrated shot.

When I struggled with under-extraction, simply adjusting the brew ratio made a noticeable improvement. If you’re not already weighing your coffee and espresso, investing in a small scale can help achieve greater consistency and control.

3. Check Your Water Temperature

Water temperature is another crucial component in espresso extraction. If the water is too cool, it won’t properly extract the coffee’s flavors, leading to under-extraction. The ideal temperature for brewing espresso is between 195°F and 205°F (90°C to 96°C).

When I realized my espresso machine was brewing too cool, it became clear why my shots were consistently sour. If your machine doesn't allow you to adjust the water temperature, ensure it's fully warmed up before pulling a shot. Some machines may take extra time to reach the optimal temperature.

For machines with adjustable temperature settings, try raising the temperature a few degrees and observe the improvement in flavor. But be careful, as water that’s too hot can lead to over-extraction, so make gradual adjustments.

4. Refine Your Tamping Pressure

Tamping, or compressing the coffee grounds in the portafilter, is another important step in espresso brewing. If you tamp too lightly, water will pass through the grounds too quickly, resulting in under-extraction. On the flip side, tamping too hard can lead to over-extraction.

In my early espresso days, I didn’t realize how crucial tamping pressure was. Ideally, you should apply around 30 pounds of pressure when tamping. It should be firm and even, creating a flat surface for the water to flow through uniformly.

A simple trick to perfect tamping pressure is to practice with a bathroom scale. Place the portafilter on the scale and press down until you reach 30 pounds of pressure. With time, you’ll develop a feel for the correct amount of force.

5. Adjust Shot Time

Shot time is another factor that influences espresso extraction. The ideal shot time for espresso is typically between 25 and 30 seconds. If your shot pulls too quickly (under 20 seconds), it’s a strong sign that the espresso is under-extracted.

To slow down the shot time, try grinding your coffee finer, increasing the coffee dose, or tamping more firmly. These adjustments will allow the water to flow more slowly through the coffee, giving it more time to extract the flavors.

Early on, I used to rush the process and didn’t realize how much a few extra seconds could affect the result. Now, I always monitor the shot time to ensure it falls within the recommended range.

6. Fresh Coffee is Key

One often overlooked aspect of espresso extraction is the freshness of your coffee beans. Coffee beans lose their flavor and complexity over time, especially after roasting. If your beans are stale, no amount of technique can save your espresso from being under-extracted and lackluster.

I used to keep my beans around for too long, not realizing the impact freshness had on my shots. Now, I make sure to use beans that have been roasted within the past two weeks. Freshly roasted beans contain more oils and soluble compounds, resulting in better extraction and flavor.

Conclusion: Achieving the Perfect Shot

Fixing under-extracted espresso is all about fine-tuning different variables—grind size, brew ratio, water temperature, tamp pressure, and shot time. While it may seem overwhelming at first, with practice, you’ll start to understand how each adjustment influences the final shot. Don’t get discouraged by sour or thin espresso; use it as an opportunity to improve and refine your technique.

In my own espresso-making journey, I found that even small adjustments can lead to significant improvements. By focusing on the details and practicing regularly, you’ll soon be pulling rich, well-balanced espresso shots that rival your favorite coffee shop. Happy brewing!