A new equation may help baristas produce the perfect espresso shot every time

Everyone's idea of the perfect cup of coffee is different. Whether you have yours black, with a splash of milk or extra sweet, you like it your way. But is there a universal law that governs how that flavor gets into your cup? According to new research published in the journal Royal Society Open Science, part of the answer lies in the permeability of the puck, the name for the bed of tightly packed coffee grains through which water passes under high pressure.