What pressure to make espresso

Beginner and pro baristas share tips and tricks for making espresso.
RaisingArizona
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#1: Post by RaisingArizona »

Hello All,

I have a Breville Double Boiler espresso machine and it has a pressure gauge front and center of the machine. Various articles claim that 9 bars is the target pressure for pulling a shot, and the range of 8-10 bars is highlighted on the gauge.

I have found that if my grind is coarse, the pressure reading will be less and flow rate will be high. Makes sense. A fine grind results in higher pressure lower flow rate. Also makes sense.

I have read that one should not fixate on pressure at all but purely rely on grind size and weight ratio of ground coffee to liquid coffee. Also saw article where a person watches the extraction color and as soon as the extraction liquid changes from dark brown to light tan, shut it down as the extraction is finished.

My question to all you baristas out there ... how important is pressure when pulling a shot? Should I even be concerned? Or should I focus on other factors?

Thanks for any advice.

Steve

Mat-O-Matic
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#2: Post by Mat-O-Matic »

RaisingArizona wrote:Hello All,
...one should not fixate on pressure at all but purely rely on grind size and weight ratio of ground coffee to liquid coffee. Also saw article where a person watches the extraction color and as soon as the extraction liquid changes from dark brown to light tan, shut it down as the extraction is finished.
Either of these methods are acceptable parameters while making shots. The first, setting a target ratio, is perhaps most common and is a good, repeatable way to approach various coffees. Roasters or folks who have experienced a particular blend or bean can recommend a brewing ratio, and you can expect a shot brewed to that ratio will be comparable to theirs. e.g. 18g in to 36g out is 1:2. Preserving the ratio will be more important than the exact numbers, and the time it takes will help you estimate how coarse or fine to grind when achieving this ratio. The second, pulling a shot until the stream turns light and just translucent, is old school, but also reliable. It may result in a longer ratio, but it will usually result in well developed sugars and a balanced shot if other variables are in the ballpark.

Pressure is important, but adds significant complexity and which may not be easy to control with your equipment and skill level. Ratio, grind, and temperature have as much or more influence over the results in your cup. There is an old adage that a pump producing 9bar pressure is a minimum requirement for an espresso machine of acceptable quality, and that's where most of the 9bar literature is pulling from. Pressure profiling, spring levers, manual levers, and various modifications can all give a barista different control over brew pressure. Some control over preinfusion pressure is desirable as a start, but not at all necessary. Many people find that the coffees they like taste best when brewed at slightly lower pressures, like 6 bar. As you explore that knowledge, recognize that water debit and rate of flow, perhaps more than pressure, are important concepts to grasp.
LMWDP #716: Spring comes, and the grass grows by itself.

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Jeff
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#3: Post by Jeff »

Mat provides some good advice!

For a machine with a fixed OPV (or bypass valve), pressure is more of an output that can be ignored than something to actively control. How the shot looks as it flows and the flow changes during the shot provides a lot of information. If you aren't hitting 4 bars or so, you probably can see that without a pressure gauge on an OPV-based machine. Even at 4 bars, there's the potential to get a good shot in the cup. Well, at least what ends up in the cup, as it might be a bit messy. I'd suggest at least tasting every shot with an open mind. If you're lucky, you get surprised and learn something new. On the other end, that single sip can reinforce your flavor memory of "off in such and such a way" for when the cues aren't as strong. Once you've given it a fair taste, then go ahead and sink it, if called for.

PIXIllate
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#4: Post by PIXIllate »

Personally I've found a significant difference in taste when using a PI/hold/bloom pressure of 2 bar vs 3 bar.

I control this through the grind setting and by when I move from the initial high flow state to a zero flow state to start the second/hold phase of the extraction.


Logically it follows that when I use the lower 2 bar PI I'll get that by using a slightly coarser grind setting than if I'm aiming for a 3 bar PI. This also usually leads to a lower peak pressure of 6-7 bar vs the potentially 8 bar peak with a finer grind and a 3 bar PI.

I don't think I can come up with a use case for anything much beyond 8-8.5 bar.