First An audible popping sound heard during roasting. In coffee, one refers to "first crack" and "second crack," which come from two different classes of chemical reactions.: An audible... ...more in one of two distinct heat-induced pyrolytic reactions in coffee. It is distinguished by a cracking or popping sound in the coffee, and occurs between 390 and 410 degrees Fahrenheit in most coffee roasters. It has a sound more similar to the popping of popcorn, whereas the After First Crack, a roast reaction around 440 to 450 degrees that is distinguished by a snapping sound. Second Crack is the second audible clue the roaster-operator receives... ...more that occurs around 440 to 450 Fahrenheit has a more shallow, rapid sound, like the snapping of Rice Krispies cereal in milk! First crack involves a rapid expansion of the coffee seed, and marks the point where water and carbon dioxide fracture, leading to the liberation of moisture from the coffee in the form of steam. First crack opens the crease in the bean enough to release remaining On dried green bean coffee, the thin inner-parchment layer that clings to the bean and lines the crease on the flat side. Silverskin becomes chaff and falls off... ...more, or Chaff is paper-like skin that comes off the coffee in the roasting process. Chaff from roasting is part of the innermost skin (the silverskin) of the coffee fruit... ...more. First crack is a clue to the roaster-operator about the roast level, and it’s termination generally marks the first stage (City roast is what we define as the earliest palatable stage that the roast process can be stopped and result in good quality coffee. City roast occurs roughly... ...more) where coffee is acceptably dark enough to enjoy.