What's the Right Grind Size for Espresso? What to Do When Your Espresso Machine Won't Build Pressure?

Quick Question! What's the Biggest Difference Between Espresso Machine Extraction and Other Coffee Brewing Methods?

That's right - it's the difference in pressure! The former uses pressurized extraction, while the latter operates under normal pressure. The presence of pressure allows espresso to be extracted in an extremely short time! The golden Crema layer on top of espresso is the exclusive product of pressurized extraction. So we can understand that pressure is a crucial parameter for espresso machines. Generally, espresso machine extraction pressure fluctuates around 9bar. Within this range, espresso can be extracted quickly while maintaining rich flavor. However, many new coffee machine owners have reported to FrontStreet Coffee that their extraction pressure struggles to reach 9bar, often staying between 5-7bar, resulting in coffee that tastes weak and watery, with excessive acidity and bitterness. So, why does this happen?

Why Is Extraction Pressure Insufficient?

Let's first discuss what "pressure" actually is. In physics, pressure is defined as the force acting on the contact surface between two objects! Simply put, it's the force perpendicular to the object's surface due to mutual compression between objects. When applied to coffee machines, it refers to the force that water exerts on the coffee puck. The main determinant of pressure limits is the resistance of the coffee puck. The greater the puck resistance, the more difficult it is for hot water to penetrate, thus requiring higher pressure, and the coffee machine naturally provides greater pressure. But when puck resistance is insufficient, hot water can easily penetrate the puck. At this point, even if we want the coffee machine to increase pressure, it cannot do so. Therefore, the magnitude of puck resistance is crucial.

When hot water can quickly penetrate the puck, it means the contact time between hot water and coffee grounds is shortened. Without pressure assistance, extraction efficiency will be significantly reduced, and the same liquid volume cannot extract sufficient flavor compounds from the coffee. This results in negative characteristics like weak, thin coffee and sharp acidity. So, if we want to extract sufficient flavor compounds in a short time, we need to increase puck resistance to improve extraction efficiency. You might want to guess what aspects can increase puck resistance, and then check your answers against FrontStreet Coffee's suggestions!

1. Adjust Grind Finer

Often, the reason puck resistance is insufficient and coffee machine pressure won't increase is largely due to incorrect grind settings. When coffee particle size is too coarse, the gaps between grounds become larger, providing ample space for hot water to flow through, naturally not requiring high pressure for extraction. Adjusting to a finer grind is the best solution! Specific adjustments need to be determined based on current extraction time. When the difference between actual espresso extraction time and the target extraction time is too large, we need to adjust to a finer setting accordingly.

2. Increase Dose

Besides grind settings, the amount of coffee used is also an important factor. Many friends might want to reduce caffeine intake, so they use less coffee. But we need to understand that each portafilter basket has a recommended dose. This limit exists to ensure reasonable space between the puck and shower head - too little won't work, and too much won't work either.

When we use significantly less coffee than the basket's recommended dose, it not only means greater distance between the puck and shower head, but also that the puck thickness is greatly reduced. This means hot water has less coffee to pass through, so it can break through the puck more quickly, thus not requiring the coffee machine to provide excessive pressure. Therefore, dose is another parameter that can determine the upper limit of pressure value. We should try to use the basket's recommended dose. If the difference is too large, FrontStreet Coffee suggests replacing the basket would be more appropriate!

3. Tamping Pressure

Don't underestimate the tamping operation! The purpose of tamping is to make the connection between coffee grounds closer, allowing the coffee grounds to condense together and form resistance. But when we apply insufficient force during tamping, the puck cannot form properly. Loose coffee grounds will leave many channels for hot water to flow through. Since there's no resistance, pressure isn't needed to break through! Therefore, the force we apply during tamping must be sufficient so that the coffee machine has room to provide pressure.

Besides these regular operations, the choice of portafilter basket can also change the coffee machine's pressure limits. The number and size of holes in the basket can control hot water flow rate, thereby affecting the coffee machine's pressure. But unless there are special extraction requirements, we only need to pay attention to the three factors mentioned above.

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Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473