The Perfect Cup

Buy loose beans in small quantities no more than a few days from the roasting date (ask before you buy); our testing has shown that roasted beans are ready for the compost pile after just 10 to 12 days. Buy from a local roaster or a store that sells a high volume, upping your chances of buying beans from a recently roasted batch.

Don't buy preground coffee. Grinding speeds oxidation and the deterioration of flavor. When we compared coffee brewed from just-ground beans with coffee brewed from beans ground 24 hours earlier, tasters overwhelmingly preferred the coffee brewed from freshly ground beans. Grinding the night before is also not optimal: Studies show that the exposed coffee cells begin to break down within an hour.

If you will finish a bag of beans in less than 10 to 12 days, store them either in the original bag or in a zipper-lock bag away from heat and light. If you plan to keep beans longer than this time frame, store them in the freezer to limit contact with air and moisture. Never store coffee in the fridge, where it will pick up off-flavors.

We’ve found some supermarket coffee brands with expiration dates as far as two years out from the roasting date. To check if your beans are fresh, scoop 1/2 cup into a zipper-lock bag and press out all the air, then seal the bag and leave it overnight. If the beans are within seven to 10 days of roasting, they will release carbon dioxide that makes the bag puff up. If the bag remains flat, the beans are not producing gas—a sign that they’ve passed the point of peak freshness.

If you like your coffee piping hot, it's a good idea to preheat your mug: Fill it with boiling water, let it sit for a few minutes, dump the water, and fill 'er up. Preheating ensures that most of the heat stays in your drink instead of being absorbed by the mug.

The most desirable flavor compounds in coffee are released in water between 195 and 205 degrees. A panel of our tasters judged coffee brewed at 200 degrees as having the fullest, roundest flavor. Once water has boiled (212 degrees), let it rest for 10 to 15 seconds to bring it down to this temperature.

Speaking of water: A cup of coffee is about 98 percent water, so if your tap water tastes bad or has strong mineral flavors, your coffee will, too. We found that the test kitchen’s tap water masked some of the coffee’s complexity compared with coffee made with filtered water. Don’t bother buying bottled water—just use a filtration pitcher.

The norm is 2 tablespoons of ground beans for every 6 ounces of water. If you prefer stronger or weaker coffee, adjust the amount of grounds per cup; changing the amount of water can easily lead to over- or underextraction, because the less water you use, the shorter the brewing time and vice versa.

These two components go hand in hand. Brewing time will dictate how you grind the coffee. In general, the longer the brewing time, the coarser the grounds should be. As a rule, brewing should take 4 to 6 minutes. Don’t try to adjust strength by changing the grind; grounds that are too fine for your brewing method will result in overextraction, while grounds that are too coarse will be underextracted.