Από το http://coffeegeek.com/guides/howtobuyanespressomachine/getagrinder
Espresso preparation is harsh. It's just about the harshest brewing method you can throw at a coffee bean and still produce something that tastes heavenly. Percolators can't do that. Even moka pots are finicky as all heck. Espresso brewing, using over 135 pounds of water pressure per square inch, extracting in 25 seconds, is near-torture for the ground coffee bean. So why does espresso just "work" for some people? Why do some home baristas and many "third wave" professionals have the ability to pound out great tasting shots of espresso? If you ask them for their secret, besides talking up good ingredients (quality, fresh roasted coffee, good water) and having a developed skillset for producing espresso, they'll all mention one other key thing: the grinder. One core item they all have in common is a quality grinder to freshly grind the coffee to the very precise particle sizes necessary to good extraction. Often, the grinder is the rock star of their little espresso show. I've often said that I can make a better shot of espresso with a $200 espresso machine and a $400 grinder than I can with a $2,000 espresso machine and no grinder (or a blade grinder)... and it's absolutely true.
και εδώ http://www.ajcoffeeco.com/blog/your-grinder-is-more-important-than-you-think/
Espresso: Precision is SignificantEspresso is made using very fine coffee particles, and require a grinder capable of producing a consistent grind at a very fine setting. The reason consistency is so important in an espresso grinder is that espresso brewing happens under a lot of pressure (9bar, or ~135psi) in a very short amount of time. Inconsistencies in grind will not only result in a varied of extraction rate, but may also result in extreme channeling.
- See more at: http://www.ajcoffeeco.com/blog/your-grinder-is-more-important-than-you-think/#sthash.3sAUuTS6.dpuf
και εδώ http://www.home-barista.com/grinders/grinder-burr-types-explained-flat-conical-drm-t1672.html