““You've had hot coffee before, and in the hands of a skilled maker, coffee can be amazing. But the fact is that coffee is one of the hardest things to get right in the world. Even with great beans and a great roast and great equipment, a little too much heat, the wrong grind, or letting things go on too long will produce a cup of bitterness. Coffee's full of different acids, and depending on the grind, temperature, roast, and method, you can "overextract" the acids from the beans, or overheat them and oxidize them, producing that awful taste you get at donut shops and Starbucks. But there is Another Way. If you make coffee in cold water, you only extract the sweetest acids, the highly volatile flavors that hint at chocolate and caramel, the ones that boil away or turn to sourness under imperfect circumstances. Brewing coffee in cold water sounds weird, but in fact, it's just about the easiest way to make a cup (or a jar) of coffee. Just grind coffee -- keep it coarse, with grains about the size of sea salt -- and combine it with twice as much water in an airtight jar. Give it a hard shake and stick it somewhere cool overnight (I used a cooler bag loaded with ice from ice camp and wrapped the whole thing in bubble wrap for insulation). In the morning, strain it through a colander and a paper coffee filter. What you've got now is coffee concentrate, which you can dilute with cold water to taste -- I go about half and half. If you're feeling fancy, serve it over ice.””
