How do egg producers sort eggs into jumbo, large, and medium sizes?

It would be nice if hens were systematically grouped into jumbo, large, and medium sizes, just as their eggs are classified.

But even though tall people often have tall children, big hens don’t necessarily lay big eggs. In a standard coop all the hens, large side by side with small, are kept in cages of 4 square feet, three or four birds to the cage. While one conveyor belt brings them their meals, another carries away the eggs that roll from their tilted cages.

Placed by either hand or machine in flats (containers holding 21/2 to 3 dozen), which are brought to a processing room, the eggs are then picked up by a suction gun, a machine with 21/2 to 3 dozen rubber suction cups that fit over the tops of the eggs.

The suction gun transfers the eggs to a conveyor belt studded with spindles; each egg is supported by two spindles, separating the eggs and thus preventing them from rattling against each other and cracking. A washing machine cleans away any debris, the pores that allow an egg to breathe are sealed with oil, and the eggs go into a candling booth. Here mirrors on the wall and very bright lights beneath the eggs allow an inspector to check for cracks or blood spots.

Finally, the eggs that pass inspection advance to a scale, which consists of a rocker arm with a weight on the back of it.

If the egg is heavy enough to tip the rocker arm, it passes from the conveyor belt into one of two lines of cups, which then lower the eggs into a waiting carton. A carton of jumbo eggs must weigh 30 ounces, so each jumbo egg must weigh 2.5 ounces; the first scale is set accordingly.

If the egg isn’t heavy enough, it automatically moves on to the next rocker arm with a slightly lighter weight behind it. There are usually five scales that separate the eggs into the various categories: jumbo, 2.5 ounces; extra large, 2.25 ounces; large, 2 ounces; medium, 1.75 ounces; and small, 1.5 ounces.

If the egg is too light to tip the last rocker arm, it won’t ever reach your local supermarket.