"20-bar high pressure." This figure, displayed in large print on the packaging and product sheets of almost every portable coffee machine on the market, has become one of the most used marketing arguments in this category—and one of the most misunderstood by buyers.
The underlying idea is intuitive: more pressure is better. As if a 20-bar machine necessarily produced a better espresso than a 9-bar machine. This logic seems consistent—but it is false. And understanding why allows you to evaluate a portable coffee machine with objective criteria rather than a marketing argument designed to impress without informing.
What does pressure in bars actually mean?
A bar is a unit of pressure measurement corresponding approximately to atmospheric pressure at sea level. A coffee machine that claims 9 bars of extraction exerts 9 times the atmospheric pressure on the water passing through the ground coffee.
For an espresso, this pressure is what forces hot water through the bed of compacted coffee in a few tens of seconds—much faster than gravity alone would. It is this forced extraction under pressure that produces the crema and releases the aromatic oils responsible for the body and complexity of the espresso.
The ideal pressure for an espresso, determined by decades of barista research and codified by the National Italian Espresso Institute, is between 9 and 10 bars. Not 15. Not 20. Between 9 and 10.
Why 9 bars is the magic number—not 20
The 9-bar pressure is not arbitrary. It is the result of a precise balance between several physical and chemical phenomena that occur during extraction.
Below 7 bars, extraction is incomplete: the water does not pass through the coffee with enough force to properly emulsify the oils, the crema is absent or very thin, and the aromas are truncated. The coffee is acidic and lacks body.
Between 9 and 10 bars, extraction is optimal: the crema forms correctly, the oils are emulsified, and the sugars caramelize slightly under the combined effect of pressure and heat. This is the golden zone of espresso.
Beyond 12 to 15 bars, over-extraction begins to produce undesirable bitter compounds—tannins and certain acids are extracted in excess, resulting in an aggressive and unpleasant coffee. Contrary to intuition, excessive pressure harms the quality of the espresso rather than improving it.
Why do manufacturers display 15, 18, or 20 bars then?
This is where commercial reality takes precedence over technical reality. In a market where buyers compare numbers without always having the knowledge to interpret them, displaying "20 bars" rather than "9 bars" creates an impression of immediate technical superiority—even if this superiority is fictional from the point of view of the quality of the coffee produced.
Most machines advertised at 15 or 20 bars actually include systems that regulate the effective extraction pressure to around 9 to 10 bars—the figure displayed represents either the theoretical maximum pressure of the pump or a peak pressure not maintained throughout the duration of the extraction.
This is not necessarily a scam—it is marketing communication that uses the most impressive figure available rather than the figure most relevant to the quality of the result.
The real criterion that matters: pressure stability
What really determines the quality of an extraction is not the maximum advertised pressure—it is the stability of the effective pressure throughout the 25 to 30 seconds of extraction.
A machine that maintains a stable 9 bars for 28 seconds produces a consistently better espresso than a machine that claims 20 bars but whose pump runs out of steam after 10 seconds and drops to 5 bars for the rest of the extraction.
This stability is not measured with a number on the packaging—it is read in user reviews that describe the presence and persistence of the crema over several weeks of use, not just during the first use on a new machine.
How to evaluate the real pressure of a machine before buying
Without professional measuring equipment, several indirect indicators allow you to evaluate the real quality of the extraction pressure of a portable machine.
The crema is the most accessible indicator: thick, golden, and persistent for several minutes signals a stable and sufficient extraction pressure. Thin, white, and disappearing in a few seconds signals insufficient or unstable pressure, regardless of the figure displayed on the packaging.
User reviews after several weeks or months of use are more reliable than first impressions—the quality of the extraction pressure is maintained or degrades with use, which only prolonged use can reveal.
The manufacturer's warranty policy is an indirect indicator of confidence: a 60-day warranty signals confidence in the durability of performance, whereas 14 days leaves little time to evaluate the consistency of extraction over time.
Conclusion
The next time you see "20 bars" in large print on a portable coffee machine product sheet, you now know that this figure says almost nothing about the actual quality of the espresso that this machine will produce. What matters is the stability of the effective pressure around 9 to 10 bars for the entire duration of the extraction—a criterion that is not read on the packaging but in the crema of each cup.
The Velmora™ is designed to maintain a stable extraction pressure that produces a thick and persistent crema with every use—not to display the most impressive figure on a technical sheet.
FAQ — Portable coffee machine pressure and bars
How many bars are needed to make a real espresso? Between 9 and 10 bars is the optimal range codified by the National Italian Espresso Institute. Below 7 bars, extraction is insufficient. Beyond 12 to 15 bars, over-extraction produces undesirable bitter compounds.
Is a 20-bar machine better than a 9-bar machine? No—the displayed figure often represents the theoretical maximum pressure of the pump, not the effective pressure maintained throughout the extraction. A machine that maintains a stable 9 bars generally produces a better espresso than a machine that claims 20 bars without maintaining them.
How do I know if my machine exerts the right extraction pressure? The crema is the most reliable indicator: thick, golden, and persistent for several minutes signals a stable and sufficient pressure. Thin, white, and fleeting signals insufficient or unstable pressure.
Why do manufacturers display such high pressures if 9 bars are enough? For marketing reasons—a high number creates an impression of technical superiority in a buyer who does not have the knowledge to interpret it correctly. This is a common practice in the portable coffee industry.
Does the pressure of a portable coffee machine decrease over time? Yes—the accumulation of limescale and residue in the internal circuits gradually reduces the effective extraction pressure. Regular maintenance (descaling every 3 to 6 months) maintains the initial performance over time.
Does regular descaling improve extraction pressure? Yes—limescale is the main cause of gradual pressure loss in hot water machines. Descaling returns the water circuits to their original state and restores the effective extraction pressure to its initial level.
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