Candling is the step during grading when the egg grader looks inside the egg (without breaking it) to judge quality. Long ago, this quality check was done by holding a candle behind an egg. Some hand-candling, using electric equipment, is still used for spot-checking or for training egg graders; however, today most eggs pass on rollers over high-intensity lights that make the interior of the egg visible. The eggs are rotated so all parts are visible. The candler checks the size of the air cell and the distinctness of the yolk outline. Imperfections such as blood spots usually show during candling. Very large packing plants may also use electronic blood and/or check detectors to sort and remove eggs exhibiting these defects.

See also Grading, Processing