Why the carton is shaped, not merely padded
An egg carton works by controlling where forces travel. The molded cups cradle each egg at several points, while the raised dividers keep neighboring shells from striking one another when a box jolts or vibrates. That separation matters: one cracked egg can otherwise become a hard, slippery impact surface for the eggs beside it.
The cups also limit how far an egg can move. A shell is more likely to break when it hits another object at speed than when its motion is gently checked, so reducing both contact and movement helps protect it through repeated bumps.
How the fiber absorbs a jolt
Many cartons are made from molded paper fiber. Its uneven, springy structure can bend and compress under a sudden load, taking some of the impact before it reaches the eggs. The carton is not an indestructible shield: a severe crush can overwhelm it. Its job is to soften ordinary handling shocks and keep them from concentrating on one shell.
The shape helps with stacking, too. The lid and projecting cup shapes can bear pressure from cartons above, channeling some of that weight through the carton rather than directly onto the eggs. In a shipping box, cartons can still be damaged if they are crushed or packed poorly, but their molded geometry gives each egg a small, stable pocket.
That is the useful compromise: a lightweight package that can deform a little, instead of passing every bump straight through to the shell.
