A coffee that has been roasted to the brink of 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 about the degree-of-roast, following First Crack. Whereas More.: A coffee that has been roasted to the brink of second 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 popping sound heard during roasting. In coffee, More. The internal bean temperature that second crack normally occurs at is 446 degrees F. But in fact second crack is a little less predictable than First crack 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 More, in my experience. Why? It could be explained as this: first crack is the physical expansion of the coffee seed as water and carbon dioxide split and CO-2 outgassing occurs. Second Crack is the physical fracturing of the cellular matrix of the coffee. This matrix is wood, also called Cellulose is the principle fiber of the cell wall of coffee. It is partially ordered (crystalline) and partially disordered (amorphous). The amorphous regions are highly accessible and react readily, but the crystalline regions with close More, and consists of organized cellulose that reacts readily to heat, and not-so-organized cellulose that does not. Since every coffee is physically different in size and The density of a coffee bean is often taken as a sign of quality, as a more dense bean will roast more with a better dynamic. The density of a coffee bean is often taken More due to the USDA is (obviously) the United States Department of Agriculture. USDA also had coffee plant breeding programs in the past and one variety they distributed to Indonesia and was widely planted is called USDA (sounds like More, In coffee talk, it refers to a coffee-producing region or country; such as, "I was just at origin." Of course "Origin" for most product we use is not a beautiful farm in a temperate climate, More, altitude, etc. it might make sense that the particular cell matrix is different too, and not as universally consistent in reactiveness as H-2O and CO-2. Presumably the name comes as a defined level a shade darker than 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 between 415 and 425 degrees Fahrenheit in More, which was an esablished level among New York City coffee roasters in the past.