"Coffee leads men to trifle away their time, scald their chops, and spend their money, all for a little base, black, thick, nasty, bitter, stinking nauseous puddle water." ~The Women's Petition Against Coffee, 1674
Coffeenoobie Senior Member Joined: 11 Dec 2011 Posts: 2,323 Location: PNW Expertise: I like coffee
Espresso: N S Oscar Grinder: Vario W
Posted Fri Mar 2, 2012, 9:33am Subject: Re: I have become... a SNOB
I have never gotten no crema at all except for the krupps steam toy. Even when I did everything wrong I managed to get some and it never just looked like black coffee.
Coffeenoobie
Buying advice: GRINDER GRINDER GRINDER. Don't cheap out on the grinder. My coffee treasure map... Click Here (maps.google.com)
Posted Fri Mar 2, 2012, 10:25am Subject: Re: I have become... a SNOB
I even get a little crema-like substance with the Aeropress. Poorly-maintained equipment, low brew pressure, very low dose, bad water, low brew temperature, old coffee, worn grinder burrs, too-coarse grind. Even with all that there is the potential for some crema. Can't imagine how old that coffee was that it produced no crema at all. I have never had a pull that had no crema.
Posted Fri Mar 2, 2012, 10:30am Subject: Re: I have become... a SNOB
frcn Said:
I even get a little crema-like substance with the Aeropress. Poorly-maintained equipment, low brew pressure, very low dose, bad water, low brew temperature, old coffee, worn grinder burrs, too-coarse grind. Even with all that there is the potential for some crema. Can't imagine how old that coffee was that it produced no crema at all. I have never had a pull that had no crema.
I'm very curious what kind of brew pressure is in the aeropress. Maybe we can get a filter disc that mimics a filter basket, do a coarser version of espresso grind and then shove the hot water through the "puck". Maybe there could be an aeropress tamper as well.
Posted Fri Mar 2, 2012, 12:03pm Subject: Re: I have become... a SNOB
The Aeropress does not develop "espresso" forces as we are accustomed to discussing them. The cylinder is approximately 2.25" in diameter. The area of the piston is 3.976 square inches. If you press with 160 pounds on the plunger (that would lift my feet off the floor), the math of force/area, it works out to about 40PSI (*1) even if the chamber were sealed at the bottom. This math would indicate that to develop 130psi you would need to press down with 520 pounds of "force." Based solely on that, it compares more closely to a moka pot than an espresso machine. The grades haven't been posted so I am not sure if I passed the test.
Posted Fri Mar 2, 2012, 12:10pm Subject: Re: I have become... a SNOB
frcn Said:
The Aeropress does not develop "espresso" forces as we are accustomed to discussing them. The cylinder is approximately 2.25" in diameter. The area of the piston is 3.976 square inches. If you press with 160 pounds on the plunger (that would lift my feet off the floor), the math of force/area, it works out to about 40PSI (*1) even if the chamber were sealed at the bottom. This math would indicate that to develop 130psi you would need to press down with 520 pounds of "force." Based solely on that, it compares more closely to a moka pot than an espresso machine. The grades haven't been posted so I am not sure if I passed the test.
ganglia Senior Member Joined: 30 May 2012 Posts: 14 Location: Seattle, WA Expertise: I like coffee
Espresso: Current: Nuova Simonelli... Grinder: Current: Baratza Preciso....
Posted Sat Aug 11, 2012, 4:39am Subject: Re: I have become... a SNOB
frcn Said:
The Aeropress does not develop "espresso" forces as we are accustomed to discussing them. The cylinder is approximately 2.25" in diameter. The area of the piston is 3.976 square inches. If you press with 160 pounds on the plunger (that would lift my feet off the floor), the math of force/area, it works out to about 40PSI (*1) even if the chamber were sealed at the bottom. This math would indicate that to develop 130psi you would need to press down with 520 pounds of "force." Based solely on that, it compares more closely to a moka pot than an espresso machine. The grades haven't been posted so I am not sure if I passed the test.
The "effective" area is the area of the holes on the filter cap: It has 97 holes, each ~3mm in diameter. = 1.062 sq inches area.
Assuming no restriction is in place (plunger/filter), to get 130PSI, you need ~138lbs.
Taking the restriction from filter into account, my hypothesis is that you need somewhat less than 138lbs to cause an effective pressure of 130psi on the coffee grounds.
Add to that the force needed to get over the plunger's restriction -> the ballpark of 130-150lbs probably makes the coffee go through 130PSI, similar to a regular espresso machine.
Im wondering if the "effective pressure" on the coffee can be measured somehow to validate this hypothesis :) Alan?
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