What Is Candling When Used for Eggs?

Eggs are candled by shining a bright light into the egg in order to see inside of the egg. Candling is done in a dark room for the light to illuminate the inside of the egg. Candling is used to determine the condition of the air cell, yolk and white.

  1. How to Candle an Egg

    • Place the candler on a table about 38 to 44 inches from the floor. The egg should be at eye level. Hold the egg in a slanting position with the large end against the hole in the candler. Quickly turn the egg to the right or left, which will move the contents of the egg and throw the yolk near the shell. Candling should be done in a dark room to better illuminate the inside of the egg. Eggs with brown shells may be more difficult to see inside.

    Embryology

    • Candling is used when raising poultry. Incubated eggs are candled to see if they are fertile. Candling of white eggs should be done on the third day after incubation to test for fertility. Brown-shelled eggs should be candled on the fifth or sixth day after incubation. The embryo of the eggs can been seen. A healthy embryo will be floating in the center of the egg surrounded by red blood vessels. The condition of the embryo is evaluated for any deformities in the development. Dead embryos or unfertilized eggs should be removed from your incubator.

    Consumable Eggs

    • Eggs raised for human consumption are candled to check for abnormalities such as bloody whites, blood spots, meat spots and cracked shells. Eggs found with any of these abnormalities should be discarded. If the egg is fresh, the air space is plainly visible and moves freely. The white is thin and clear.

    Commercial Egg Producers

    • Commercial egg producers use highly automated egg candling machines. All eggs are processed through the candling machine to check for abnormalities and fertilization. The machine is able to view the inside of the eggs and automatically discard any that do not meet standards. Through candling, the eggs are graded according to the standards set by The U.S. Department of Agriculture.