How does flash candling detect cracks and defects inside eggs?

Flash candling is an egg-grading process used in commercial production to ensure quality by inspecting eggs before a strong light source in a darkened environment.12

By passing eggs over this intense light, the process allows for the visual detection of internal and external abnormalities. The light penetrates the shell, revealing defects such as cracks, blood spots, or other irregularities that would otherwise be hidden from view. This method is essential for sorting eggs into appropriate quality categories, as higher-grade eggs must possess a clean, smooth, and unbroken shell.12