For Mark and Other Espresso People
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https://www.seriouseats.com/best-espresso-grinders-7377134
We Tested 7 Espresso Grinders—4 Ensured Excellent Results Every Time
Brewing espresso is all about control. When you start an espresso machine, around 600 pounds of pressurized water starts to push against the coffee in the filter basket. The only way to control how fast that water moves through the coffee (and how good your espresso will taste) is to find the right grind size. And the correct grind setting will only be a few microns different than an incorrect one—invisible to the naked eye. Instead, grind size is measured by timing your shots, and an espresso that pulls in 24 seconds might be so-so, while a 28-second shot could be top-notch. That four-second difference might seem difficult to nail, but that’s the level of control a great espresso grinder has.
However, most standard burr grinders can’t get fine enough for espresso, and the ones that do aren't precise enough to offer multiple settings in that range (as we found out in our coffee grinder testing). Espresso grinders, on the other hand, have burrs that are distinctly calibrated for precision and consistency at super-fine settings, letting the user tweak their grind and fine-tune their shots. To find the best espresso grinder, we tested seven models at a variety of price points. (Note: We didn't include any heavy-duty commercial grinders.) We found four favorites that will suit espresso novices and nerds alike.