HOW MANY BARS OF PRESSURE FOR ESPRESSO? HACK YOUR ESPRESSO

What’s the right pressure to pull a shot of espresso? The answer is more nuanced than you’d expect.

Pressure is one thing that sets espresso apart from other types of coffee. While you might be able to get a short, concentrated brew out of a range of coffee machines, high pressure is essential to create the signature richness and crema we love.

When it comes to just how much pressure is needed, you might see a few different figures suggested – not to mention some confusing marketing hype. So just what is the right espresso pressure to extract a well-made espresso?

What Do We Mean By Bars Of Pressure?

Let’s start by clarifying some terminology. If you’ve ever put air in your tires, you’ll be familiar with measuring pressure in pounds per square inch (psi). A bar is simply an alternative unit of measurement, the way that kilos and pounds are two ways of measuring mass. 

The bar is not one of the International System of Units, but it’s commonly used in things like scuba tanks and, of course, espresso machines (1).

Bars are a metric unit, with 1 bar being approximately equal to atmospheric pressure at sea level. So when we talk about an espresso maker using 9 bars of pressure, it means the water is forced through the coffee grounds at a pressure nine times that of the natural atmosphere.

How Is Pressure Generated In Espresso Machines?

The original espresso machines used steam pressure, but with the advent of electricity, this was largely replaced by vibratory or rotary pumps in automatic or semi-automatic machines (2). Modern manual espresso machines use either a direct lever or spring piston to create the pressure needed to extract espresso.

There are also pressure-based coffee brewers. For example, the Moka pot relies on steam pressure, while the Aeropress has an airtight plunger. Neither approach the high pressure of an espresso machine, which is why they brew strong coffee rather than true espresso.

How Many Bars Of Pressure For The Best Espresso?

Several factors go into creating the perfect shot of espresso: brew ratio, brew time, and brew temperature. Other variables like espresso grind size, brew pressure, and tamping pressure all impact these three. 

Traditionally, around 9 bars has been considered the ideal pressure for espresso. It extracts the right combination of bitterness, sweetness, and acidity while delivering a creamy mouthfeel and rich layer of crema.

The higher the pressure, the faster the coffee is extracted from the grounds. Theoretically, you can get a quicker cup of coffee by amping up the pressure, but that speedy espresso extraction will mess with the taste of the espresso by throwing off the balance. There’s a reason that the suggested brew time for espresso is between 25 and 30 seconds.

What About The Turbo Shot?

That said, espresso machines and extraction conditions were developed in Italy along with traditional Italian espresso blend coffee. These blends tend to be dark roasted, often including Robusta and Arabica beans. 

The growing popularity of third-wave specialty coffee for espresso has encouraged some baristas to experiment with different conditions to suit these lighter roasts – and the palates of modern coffee lovers.

The turbo espresso shot is one such novel development. It’s pulled using 6 or 7 bars of pressure, a coarser coffee grind, and a shorter 15-second extraction time. Counterintuitively, these low pressure conditions actually result in a higher extraction yield and more consistent extraction, making them particularly popular in busy cafes (3).

Is 15 Or 20 Bars Better For Espresso?

You have probably seen many home espresso machines advertised as having 15 bar, 19 bar, or 20 bar pumps. They may even have some associated marketing suggesting that higher pressure is better. This is patently false, so don’t be fooled.

No matter the pressure of the pump, it’s the amount of pressure at the group – where the hot water hits the coffee grounds – that matters.

A common feature in any good espresso machine is a valve called the Over Pressure Valve (OPV) that bleeds off extra pressure to ensure you’re brewing espresso at or near the ideal pressure of 9 bars. In many higher-end machines, that valve is even user-adjustable, so you can tweak your extraction pressure to optimize your shots.

What Is Pressure Profiling?

Pressure profiling is a relatively recent development in espresso making that entails adjusting the pressure during the extraction phase. This provides a new variable for a skilled barista to tweak in search of the optimal extraction conditions.

Certain high-end automatic espresso machines now come with flow profiling options. And, of course, all manual lever machines allow users to adjust pressure simply by changing the force they put on the lever.

Final Thoughts

How many bars should an espresso machine have? In a nutshell, nine bars of pressure are recommended to create a great espresso shot, especially if you favor traditional-style espresso coffee beans. However, when choosing an espresso machine, don’t worry too much about the advertised bars of pressure; just look for a high-quality, reliable pump.

If you found this article fascinating and are keen to explore the technical aspects of espresso, consider shopping for a manual espresso machine or an automatic machine with a pressure gauge and adjustable pressure.