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Comment by qbasic_forever | Hacker News Reader

Espresso is typically made with 9 bar of pressure.

An aeropress doesn't actually generate any pressure. It just moves a column of water through a puck of coffee like a percolator. You can buy some special add-ons for the aeropress that cause it to build pressure but it's really just for generating more foamy/crema brew and not getting a proper espresso shot out of it. All that said the aeropress is still awesome and a great way to brew coffee, it's just not going to replicate espresso shots.

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> Espresso is typically made with 9 bar of pressure.

That’s certainly what I do. In the geek world though, they are going a lot lower. I’ve seen 6 mentioned and 7 or 8 is common.

There is also the effect of the pre-infusion which is a lot lower.

I haven’t explored this world, but there are plenty of die hard proponents of it.

About the Aeropress, I guess the question is: When I press it down (in my case, using the elbow for added pressure) how many bars can a typical user reach?

Maybe 1 bar. You need a big lever or pump to get more than that. Check out the Flair or Wacoco brands if you want entry level manual espresso.

Let's do a little calculation. For an upper bound, let's say you press your full weight onto it and the coffee grounds' resistance is not the limiting factor. That's maybe 90kg, times the acceleration of gravity, for about 900 newtons. That force is applied to a pi*(30mm)^2 or ~3^-3 m^2 area. That gives us a pressure of 900/3e-3 = 3e5 Pa or 3 bars.

Getting over 1 bar gets you to a spray of coffee that sprays everywhere: https://youtu.be/Qz_GZpzpst4?t=500

why does he have it so far away from the cup?

Hoffmann measured this with a pressure sensor modded aeropress - most typical brews would not exceed half a bar.

James Hoffmann answered this with a modded aeropress with a pressure sensor: a typical aeropress brew is in the range of half a bar. The max he could achieve was 1.5 bars, but like he says, no one brews like that. He also found anything past 0.5 bars began to taste awful.

https://www.youtube.com/watch?v=jBXm8fCWdo8

No. The aim of the aeropress is good extraction , not foam/cream. And i doubt you get 9 bars from that thing in the photo. Therefore i suggest an aeropress (and learn about extraction and taste) instead of building a machine without understanding the principle of brewing a shot. For which you need a ceramic grinder by the way. But do not get me wrong, i am all for open source and building things. It might not be about coffee though.

What? The way you are responding to qbasic doesn't make sense.

Their point was simply that the high pressure attachment only creates the superficial appearance of crema, not actual espresso.

Indeed I seem to have misread the answer, and have answered poorly. Thanks for pointing that out. My point is that understanding taste, grinding and extraction will take you a long way. One of the keys for extraction is fixing the variables. If you for example have a steel grinder that does not grind evenly(and burns or heat the coffe with friction) the resulting extraction is a result of hazard. You will have both overextracting and underextracting.In the same way not having consistent ( enough) pressure will give poor results. There are ways to compensate but you are going to have «errors» in the taste. I have trained as a barista, trained with scent kits, and have been given enough home coffe brews (supposely espresso) by coffe fans made with home machines that I lost hope in any of those machines. Really experiencing taste while limiting the method is more benefical in my opinion. And kust to be extra clear I am not saying that an aeropress gives you an espresso shot.

Almost nobody is using ceramic burrs. All the top grinders you see in people's homes and most cafes will be using steel burrs.

Your EK43's, Mythos Ones, EG-1s etc have steel burrs.

The builder reuses the pump from a real espresso machine. It might not reach exactly 9 bars, but it's between 7 and 9. I don't know where your skepticism comes from.

Source: I own and repair espresso machines as my hobby and for my daily coffee habit.

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