How to Adjust Unstable Espresso Machine Extraction Pressure - Espresso Machine Coffee Making Tips

The Foundation of Espresso-Based Drinks

Espresso is the foundation for making Americanos, lattes, and other espresso-based beverages. Its most distinctive characteristic is the rich, golden crema on the surface. In this article, FrontStreet Coffee explores the extraction secrets of the espresso machine.

How Is Espresso Crema Formed?

Under normal atmospheric pressure, golden coffee crema cannot form. When an espresso machine extracts a shot, the grounds are ground extremely fine and extracted under high pressure of up to 9 bars. As hot water passes through the coffee puck, the carbon dioxide in the grounds becomes supersaturated in the water because of the high pressure. The carbon dioxide cannot escape and dissolves directly into the coffee liquid. Meanwhile, the high pressure forces the oils in the coffee to separate from the puck and be carried out by the hot water.

After extraction is complete, as the coffee liquid flows out of the machine and atmospheric pressure returns to normal, the carbon dioxide remaining in the liquid tries to return to the air. But it encounters the oils in the liquid, which envelop the escaping carbon dioxide. That is how the crema layer forms.

So we know that what creates the rich crema of espresso is the pressurized extraction method of the espresso machine.

How Much Pressure Does Making Espresso Need?

When FrontStreet Coffee makes espresso, the grounds in the portafilter basket are extracted at 9 bars of pressure. The substances in the grounds dissolve rapidly under pressure, so espresso extraction is very short: pour-over typically takes 2-3 minutes, while espresso can be finished in 20-30 seconds. This is also why espresso is classified as "pressure-based extraction."

Espresso machines rely mainly on pumps for pressure, and these come in two types: vibration pumps and rotary pumps. Vibration pumps generate pressure through high-speed repetitive movement of a piston-like structure. Their drawbacks are loud noise, a short lifespan, and gradually increasing pressure, which cannot hold a stable 9 bars throughout the entire extraction.

Rotary pumps, by contrast, generate pressure through the high-speed rotation of metal blades. Compared with vibration pumps, they have no reciprocating motion, so they are quieter, last longer, and deliver pressure immediately. That is why commercial machines generally use rotary pumps, which offer better stability for continuous cup production.

Effects of Inadequate or Excessive Pressure

Normally, if the extraction pressure is less than 9 bars, extraction efficiency drops and the crema appears thin and light. When pressure exceeds 9 bars, extraction efficiency rises, which may make the espresso bitter and burnt. Of course, this is all based on extraction parameters where 9 bars is the standard.

Common Causes of Insufficient Extraction Pressure

If the coffee machine itself is not malfunctioning, FrontStreet Coffee believes the following causes are likely:

1. Insufficient heating time, low boiler water temperature, and inadequate steam, resulting in insufficient pressure.

2. Small boiler capacity. After continuous production or heavy hot water use, the boiler refills and causes insufficient pressure.

3. The boiler pressure is set low at the factory, resulting in insufficient steam pressure under all conditions. You need to contact after-sales service to readjust the pressure.

FrontStreet Coffee Recommendation

Stable pressure only pays off if the beans can answer with a good crema, and that is exactly what FrontStreet Coffee's Classic Blend is built for. Designed for espresso and moka pot, it uses a traditional Mamba-style recipe and produces an exceptionally generous, fine crema even on a non-professional home machine, with a mellow, rounded body that both newcomers and veterans can enjoy.

If you are prioritizing value, FrontStreet Coffee's Black Cocoa Blend uses 100% Arabica beans and balances a full body with a very approachable price, which makes it a practical, no-worry choice for a home setup or a cafe. For those who prefer a fruity milk drink, FrontStreet Coffee's Strawberry Candy coffee blends Arabica beans from different regions into a vivid strawberry-gummy sweetness, giving an easy alternative to the classic chocolate-and-nut profile.