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How to Make Espresso? What Factors Affect the Extraction of a Shot of Espresso?

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Every time you drink espresso, you find it bitter and astringent? Maybe you're not approaching it the right way! Making espresso might seem simple—just grind the beans, tamp them, lock the portafilter, and press a button, right? Not quite! In fact, there are many important details to consider within just a few minutes! First, let's look at the coffee beans! That's right, if you want to produce a consistent

Every time you drink espresso and find it bitter and astringent? Perhaps it's because you're approaching it the wrong way! Making espresso seems simple - just grind, dispense, tamp, lock in, and press a switch! But that's not the case. In fact, within these few short minutes, there's quite a bit of technique involved!

The Importance of Coffee Beans

First, let's look at the coffee beans! Yes, that's right - to make a consistent espresso, the coffee beans are very important!

Generally, FrontStreet Coffee recommends resting their espresso beans for about ten days. But everyone knows that dark-roasted beans degas faster than light-roasted ones. So why do we recommend such a long resting period?

This is because when making espresso, unlike pour-over coffee, there isn't enough space for the coffee to degas properly. If the coffee beans are too fresh with vigorous degassing, channeling can easily occur, leading to inconsistent espresso extraction.

Grind Size Adjustment

Once you have suitable coffee beans, you need to consider the grind size for espresso! This is basically something that needs to be done daily - adjusting the grind. The grind size for espresso isn't fixed at just one setting. When should you adjust the grind size?

Situations where grinder adjustment may be needed:

1. When temperature, air pressure, or humidity suddenly changes: This is especially noticeable in open spaces.

2. When replacing coffee beans: When one bag of coffee beans is used up and a newly opened bag is added. Because newly opened coffee beans may have different roast dates, batches, or resting periods, leading to varying extraction results.

3. Continuous brewing: After 5-6 consecutive extractions, the grind size may suddenly become much finer. This is because continuous use of the grinder transfers heat from the motor to the burrs, plus the heat generated by friction between the burrs and coffee beans, causing the gap between upper and lower burrs to become finer due to thermal expansion and contraction.

The moisture content and storage time of coffee beans are constantly changing, and the wear level of grinder burrs also changes over time. Therefore, baristas should regularly adjust the grinder to ensure the ground coffee powder remains perfect.

When coffee beans enter the grinder, the burrs crush them into powder. The smaller the distance between the burrs, the finer the coffee beans will be ground into smaller particles.

The finer the ground particles, the more compact and dense they become, making it more difficult for water to pass through, thereby significantly extending the extraction time.

Conversely, if the distance between the burrs increases, the ground particles become coarser, water passes through more easily, and extraction time becomes faster.

Typically, FrontStreet Coffee uses previous extraction parameters to make espresso, with time controlled within 25-30 seconds. Single dose is 13-14 grams, while double dose is around 20 grams.

After eliminating factors like puck perforation, if extraction time becomes longer, it might indicate surface over-extraction with under-extraction inside,表现为尖酸, because sweetness is insufficient, followed by bitter, astringent mouthfeel, then possibly the grind is too fine - adjust slightly coarser; but if coffee flow becomes faster, with thick water flow, shallow extraction, whitish color, and sharp acidic flavor, then possibly the grind is too coarse - adjust slightly finer.

Dosing Techniques

Once the grind size is determined, it's time for dosing!

Dosing is the first step of distribution. Uneven dosing greatly misleads and affects subsequent distribution steps. Even with advanced distribution tools, you cannot completely ignore the impact of dosing on espresso extraction.

Impact of Uneven Dosing

1. Flavor differences: If dosing is uneven, it's impossible to remedy the distribution of the lower powder layer during distribution. Uneven density distribution in the powder layer leads to uneven puck thickness and different water flow speeds at different positions during extraction. Slight carelessness can easily lead to perforation, channeling (water's inertia makes it choose easy paths while ignoring others), causing parts of the puck to be under-extracted while others are over-extracted, making each cup's coffee flavor inconsistent.

2. Large discrepancies in extraction parameters, leading to adjusting the grinder for half a day only to find flow rate wrong, time wrong, and grind size still wrong. Wasting a pile of coffee beans yet unable to achieve stable output.

How to Practice Dosing

1. Prepare an electronic scale.

Weighing and dosing before each extraction is essential for making perfect espresso. Even with a dosing grinder, I recommend regularly checking the accuracy of your grinder's weighing. After all, even the most advanced machines can have errors and malfunctions.

2. Rotational dosing.

Whether manual dosing or direct dispensing, as long as coffee powder doesn't fall completely vertically, under the influence of horizontal acceleration, the powder layer will still show some degree of bias. For example, when manually dispensing, the effect of forceful dispensing versus gentle dispensing is different - the more force, the more it leans left.

This requires maintaining uniform dispensing speed while uniformly rotating the portafilter to ensure powder is evenly distributed to different positions in the basket - of course, absolute uniformity is impossible, but it's much better than fixed-position dosing.

3. Light tapping and gentle patting.

After dosing, lightly tap on the holder or table to effectively eliminate large gaps in the powder layer. Whether fluffy or dense, uniform or not, the distribution state of the powder layer becomes clear at a glance. Slightly coordinated horizontal patting can achieve sufficiently perfect distribution effects even without additional distribution techniques.

Distribution Methods

After dosing comes distribution!

Common distribution methods include the following:

1. Leveling Distribution Method

Leveling distribution has three great tools: bean hopper lid, bamboo paddle, and fingers. Leveling distribution is one of the most common and earliest techniques beginners encounter, usually combined with back-and-forth pushing motions, divided into "four-direction distribution" (leveling front, back, left, and right) and "rotational distribution" (360-degree rotational leveling), etc.

2. Light Tapping and Gentle Patting Method

Light tapping and gentle patting are two actions but usually used consecutively. Quickly pat the bottom of the portafilter with your palm to shake the powder pile evenly, then supplement with vertical gentle tapping to effectively eliminate large gaps in the powder layer, making the coffee powder pile denser while increasing the amount of powder that can be accommodated in the basket.

3. Tool-Assisted Distribution Method

When it comes to tool-assisted distribution, various methods shine. According to the various tools on the market, they mainly fall into several categories: ① Stirring or shaking; ② Leveling the surface; ③ Screen dispersion; ④ Rotational distribution.

Checking Distribution Quality

If during the extraction process you notice the coffee liquid flow quickly becomes unstable, with large jumps and color quickly becoming very light, you can determine: there are problems inside the puck (cracks appeared) or uneven tamping caused areas with less coffee powder to be over-extracted (which may also be caused by uneven distribution leading to uneven tamping) or simply uneven distribution, leaving edge areas uncovered by coffee powder, causing water to flow directly through there.

After extraction is complete, remove the portafilter and observe the puck's shape. If edge areas have no coffee powder, or coffee powder is floated up, or the puck has obvious gaps, then it's extraction failure caused by uneven distribution.

Tamping Techniques

After proper distribution comes tamping.

Purpose of tamping: Use a certain pressure to make loose coffee powder compact, so that pressurized hot water can penetrate evenly.

The direction of tamping is vertically downward. If tamped at an angle, the high-temperature, high-pressure hot water from the group head will seek the path of least resistance for penetration, causing uneven extraction. It also easily leads to what we commonly call channeling.

The amount of tamping force and what tamper is used doesn't matter much, as long as the powder is compacted. Therefore, maintaining consistent tamping force each time becomes more important.