A coffee that has been roasted to the brink of second crack. 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 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 out gassing occurs. Second Crack is the physical fracturing of the cellular matrix of the coffee. This matrix is wood, also called cellulose, 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 density due to the cultivar, origin, 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.