Best Pressure for an Espresso Machine and Why Does It Matter?

Many of us love enjoying a good cup of espresso in the morning, as a decadent dessert, or just as a special treat to let ourselves know we did a good job today.

Luckily to be a coffee enthusiast you don’t have to know all the ins-and-outs of how these espresso machines work, because as complex as our robust, dark libations maybe they’re nowhere near as involved as the machines themselves.

If your intention is to use these machines to any degree of success you don’t need to go overboard delving into the abyss that is espresso machine internals, but there are a few things you should know whether you’re an at-home aficionado or a competition hopeful.  Just remember, ‘9 bars’.

A Mild Idea of How an Espresso Machine Works

Understanding how an espresso machine works to the mechanical layperson is a bit like watching a Star Wars movie to the uninitiated.

If the person of average know-how were to pop one of these technical wonders open it would likely resemble an H.R. Geiger biomechanical painting or one of those Perplexus puzzle games with the insane ball maze inside a plastic globe.

There are different types of machine used to make espresso, all of which are meticulously engineered and rely on first building pressure to produce the desired flavor, texture, aroma and robustness of your perfect shot.

The idea here is to use pressure to force very hot water through tightly wadded coffee grounds, which squeezes any inclusions such as air and oils outward producing a silky, rich beverage.

It takes specialized equipment to properly control the pressure but matter how the machine chooses to do it the outcome is the same.

What’s the Difference Between Espresso and Drip Coffee?

Again, the main difference is pressure.  9 bars of it to be exact.

In your regular cup of drip joe, the standard technique is to loosely heap spoonfuls of either preground coffee into the drip machine or percolator basket and send hot, unpressurized water over it where it then collects into the carafe.

Alternately, making espresso requires the buildup of pressure to force 1.5-2 ounces of not-quite-boiling water through tightly packed grounds, extruding a denser, more concentrated version of the tasty ambrosia eliminating with crema or foam on top.

The action of creating a dense puck with your finely ground coffee creates resistance against the pressurized water, and the combination of high temperature and pressure enable you to force incredible amounts of flavor into a relatively tiny vessel.

Due to the pressurized system, the brewing time of espresso is drastically reduced and takes normally around 25 to 30 seconds to pull a shot whereas a standard drip machine takes about ten minutes for a full pot.

Espresso beans are roasted longer than standard brew coffee and have more flavor producing oils, so be sure to avoid ‘washed’ beans if at all possible.

As it turns out, a cup of drip coffee contains roughly 33 percent more caffeine overall than a shot of espresso, but the standard shot is smaller by around six times in volume.

How Much Pressure Is Enough?

Obviously, due to the fact that the grounds are so firmly pressed when practicing this form of coffee extraction, there has to be enough built pressure to force the water through the puck effectively.

It seems that this day and age that the ‘industry standard’ is considered 9 bar or about 130 PSI, but some may find they strike their own gold somewhere slightly outside of this range and that is completely fine.

It is important to remember that this is the standard preferred pressure, but outside circumstances like altitude may play a role in your espresso perfection so beware.

Does It Matter if You Live at a High Altitude?

If you reside in an area of higher altitude it may be a good idea to get out of the practice of eyeballing your coffee measurements.

By using a scale and making your coffee by weight rather than visually you will be more able to dial in exactly how much you need.

It’s a good idea to write down your findings in a little notebook to cut out the guesswork should you find yourself at such an altitude again.

Being that espresso is of such a finely detailed construction, it is imperative to know how your machine will react to different atmospheric pressures and grinds.  This way you will have at least an idea of your tamping technique and fineness and the rest will just be finagling.

You might have to mess with the coarseness and amount of grind you use to get your perfect shot dialed in perfectly, but if you stick with 9 bars you’re sure to be making some pretty good espresso.





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