López-Alt's analysis of what produces crispy poultry skin identified four necessary conditions — all of which must be met simultaneously. Missing any one produces either leathery, soft, or unevenly crisped skin. The analysis applies beyond poultry to any protein skin (fish, pork crackling) where the goal is a dry, shattering exterior.
A framework for understanding and reliably producing crispy skin on poultry or other proteins by addressing all four conditions that must be present simultaneously: dry surface, sufficient fat, high heat, and surface-to-heat contact.
SALT FAT ACID HEAT + THE FOOD LAB