Everything You Need to Know About Espresso Extraction: The Art and Science Behind the Perfect Cup

Espresso (and not espresso!) is more than just a drink. It’s a perfect alchemy where every parameter plays a crucial role. Understanding the elements that influence extraction is the key to making an exceptional espresso. In this article, we dive into some of the details of espresso extraction: from extraction rate to grind, timing, machine, and more.

1. Espresso extraction: what is it?

Espresso is a method of extraction where a small amount of hot water (usually between 88 and 96 °C) is forced under high pressure (at around 9 bars) through a finely ground coffee cake. The result is a concentrated, creamy, richly flavoured beverage topped with a rich cream, the crema.

But what separates a perfect espresso from a failed one is extraction. The idea is to extract the soluble compounds from the coffee optimally, without falling into under-extract (too acidic and bland) or over-extract (too bitter).

2. The extraction rate: the perfect balance

Extraction rate refers to the proportion of soluble coffee compounds that are extracted into water. Typically, an optimal extraction for espresso is between 18% and 22% .

• Under-extraction (<18%): The water didn’t have enough time to extract the sugars and essential oils from the coffee. The result? An acidic, overly diluted, and uncomplex cup.
• Over-extraction (>22%): The water has extracted too many bitter compounds, resulting in a cup with overly pronounced roasted aromas, dominant bitterness and a lack of balance.

Finding the right balance depends on many factors, which we'll explore below.

3. The grind: the basis of a successful espresso

The grind (always fresh, therefore) is undoubtedly one of the most critical parameters for espresso extraction, and the one over which you have the easiest control. A grind that is too coarse will allow the water to pass too quickly through the cake, leading to under-extraction. Conversely, a grind that is too fine will slow down the flow of water, risking over-extraction.

To find the correct grind size:

• Use a quality coffee grinder to ensure consistency and a consistent grind from one coffee to the next.
• Adjust the grind according to the flow rate: an espresso should flow in 25 to 35 seconds for a standard dose (see below).

4. Dose and ratio

The dose refers to the amount of ground coffee used to prepare an espresso. Most standard espresso recipes recommend:

• Dose: Between 16 and 20 g of ground coffee.
• Ratio: Approximately 1:2 , which means that for 18g of coffee you get 36g of espresso drink.

This ratio can vary depending on personal preference or the particularities of a specific coffee: a ristretto will have a tighter ratio, like 1:1, while a lungo will be more diluted, around 1:3.

5. Extraction time: the espresso clock

The ideal extraction time for an espresso is between 25 and 35 seconds . This timing ensures that the water has enough time to properly extract the aromatic compounds without saturating the cup with bitterness.

Here are some signs that your timing is off:

• Extraction too fast (<25 sec): Under-extraction, acidic and too light coffee.
• Extraction too slow (>35 sec): Over-extraction, bitter and heavy coffee.

If the timing is incorrect, adjust the grind or tamping pressure to correct the flow rate.

6. The machine: equipment makes the difference

Not all espresso machines are created equal, and the right equipment can make a significant difference in your extraction. Here are the features to look for:

• Stable pressure: A machine capable of maintaining a constant pressure of 9 bars is essential (and only 9 bars, beyond that it is of no interest).
• Temperature Control: Precise and stable temperature between 88 and 96°C ensures uniform extraction.
• Filter holder quality: A brass or stainless steel filter holder ensures better retention and prevents thermal shock.

For hobbyists, a quality machine with a high-performance grinder is the best combination.

7. The importance of tamping

Tamping the coffee into the filter holder may seem trivial, but it is an essential step. The tamping must be uniform and firm enough (around 15-20 kg of pressure) to ensure a balanced extraction. In short, neither too much nor too little.

A poorly tamped patty can cause “channels” in the coffee, where water flows through too quickly, creating an uneven extraction.

8. Test and adjust: the quest for the perfect cup

Making the perfect espresso is a process of trial and error. Every coffee is unique and reacts differently depending on the settings. Don't hesitate to:

• Change the grind size.
• Test different ratios or extraction times.
• Experiment with water temperature.

Write down your settings and see how they affect the final cup. Mastering espresso takes time, but every bit of progress is worth it.

9. Common mistakes and how to avoid them

Here are some common mistakes baristas make and how to fix them:

• Bland or sour cup: Grind too coarse or extraction time too short. Adjust by refining the grind.
• Excessive bitterness: Grind too fine or over-extraction. Try a coarser grind or reduce the time.
• Insufficient cream: Old beans or poorly tamped coffee. Use fresh coffee and ensure even tamping.

10. Why is espresso a true work of art?

Because it combines science, technology and creativity. Every parameter, from the extraction rate to the temperature, contributes to creating a unique drink, revealing the full aromatic potential of the grain.

At Le Petit Jus , we value this art by working with precision-roasted specialty coffees. The goal? To offer you an unforgettable espresso experience, cup after cup.

In short

Making the perfect espresso isn’t just about technique, it’s about passion. By understanding the elements that influence extraction—grind, timing, machine, pressure—you can take your coffee to a whole new level. So, break out your grinder, preheat your machine, and start your quest for the perfect cup. Each trial and error will bring you closer to the right, perfect one.