Home espresso enthusiasts often say that if they could change one thing about the early days of their espresso equipment purchases, they would have invested in a better grinder. While there are a multitude of factors that play a part in a high quality shot extraction, the impact of the coffee ground itself cannot be overstated.
Machines like the Rancilio Silvia, for example, are particularly sensitive to the consistency of the coffee grounds, requiring a higher-end burr grinder that will ensure uniformity. Burr grinders achieve this by pulverizing the bean between two grinding wheels: Basically, the beans fall down between the wheels and the inner wheel turns, mashing the beans against the outer wheel. Depending on the coarseness level of the grind that you selected, the wheels will either be closer (for a fine grind) or farther (for a coarse grind) apart. The position of the wheels determines the size of the particles that will be deposited into the grind compartment, thus ensuring a more uniform consistency.
Because the coffee is more thoroughly ground with with this type of machine, more of the surface area is exposed on each particle and results in a richer taste.
If a burr grinder is a mortar and pestle, a blade grinder is a chef’s knife. Featuring spinning blades that chop up the coffee beans, this kind of a grinder is fast and easy, but lacks in the customization department. Additionally, because it’s chopping up the beans instead of pulverizing them, it doesn’t have the ability to ensure a consistent and uniform size of coffee ground. Lots of people use blade grinders for fresh or dried herb preparation and they work really well for that application.
Blade grinders are certainly cheaper than burr grinders, and really are suitable choices if your coffee habit is served via French Press or drip coffee.