To candle an egg, hold the small end of the egg between your thumb and first two fingers. Place the large end up to the candling light in a slanting position (see Figure 1). You can see the air cell and the yolk shadow within the albumen.
It's wise to keep the more pointed end of the egg facing down. I very occasionally candle with the blunt end down to be able to see the embryo more clearly, but it does run the risk of damaging the embryo, particularly in the first couple of weeks.
Candling detects bloody whites, blood spots, or meat spots, and enables observation of germ development. Candling is done in a darkened room with the egg held before a light. The light penetrates the egg and makes it possible to observe the inside of the egg.
Candling before the hatch
We finish rotating chicken eggs at 18 days and duck eggs at 25 days. After this time, the chick is positioning itself, ready to emerge. Some books suggest candling eggs at 18 days; however, I don't usually look at them again after 14 days.
Signs of development will typically appear as a dark spot surrounded with numerous blood vessels. If this is what you see, then congratulations, your egg is viable and contains a chicken embryo. An unfertilized egg will not show any development at this stage and will simply appear clear when candled.
Day 15. What is this? You can see here how the embryo is now filling a large part of the egg. Candling at this point provides a view of the vein - just above the air cell - moving quite energetically as the chick positions itself for hatching.
It is always imperative to only handle your hatching eggs with very clean hands. Over-handling, e.g. over-candling, will increase the potential of an egg getting contaminated from dirty hands, a sneeze or anything else!
Quitters — When embryos stop growing, we call them "quitters." You will see a thin, blood ring around the yolk. Quitters are removed from the incubator and thrown away. If you want to view the embryo, have your parent or teacher help you open the egg. Be sure to wash your hands afterwards.
The main indication that an egg is a quitter is the development of a blood ring. A blood ring looks like a well-defined red circle, which is visible on the inside of the shell. It forms when the embryo dies and the blood vessels supporting it pull away from the center and rest against the shell.
To a poultry operation, candling eggs at regular intervals lets you monitor the development of the embryo and can save you a few surprises down the road. Candling eggs is not complicated. It takes a few supplies and only a few minutes. You need a dark room, a bright light, and the egg you intend to candle.
You will need a bright light to look at your eggs, and your room will need to be dark. Poultry supply or farm supply stores sell egg candling devices, but you can also make your own. Take a 60 watt light bulb and a coffee can. Make a hole with a one-inch diameter in the top.
Eggs may be candled after 5 days of incubation and every few days thereafter. For best results you should candle eggs in a darkened room or in dimly lit conditions. The candler should be held right against the shell at the larger end of the egg where the air sac is located.
Stop egg-turning at day 18 with the larger end of the egg facing up. At this point, the chick will position itself for hatching inside the egg. Maintain a temperature of 100.5 degrees Fahrenheit but increase humidity to 70 percent.
Around day 20, as the chick prepares to hatch, you will be able to hear chirps from inside the egg. If you candle at this point, you will be able to see the chick's head poking up into the air cell. This indicates that the chick is preparing to hatch. White eggs are easiest to see into when candling.
The blood ring itself is just that - a ring of blood vessels. Of course, decomposing matter does produce bacteria but that's not what you can see when candling an egg. What you can see is the decomposing circulatory system, as you can see very clearly if you open the egg.
Even though most hens will get this right, it is still possible that some embryos will die and the eggs will rot, or there will be eggs that aren't fertile. Your broody hen will usually be able to tell if an egg is rotten, and she is likely to push it out of the nest; however, it's an idea to candle the eggs.
Starting on day 10, the eggs will benefit from daily misting and cooling. Once a day, remove the lid of the incubator and leave it off for 30-60 minutes. The eggs should be left so they feel neither warm nor cold to the touch. Then mist each egg with lukewarm water and replace the incubator lid.
Early deaths: The embryo has developed for several days and then died. Candling will reveal a small dark area and disrupted blood vessels. Often deteriorating blood vessels will appear as a dark ring around the egg. Discard.
* You can candle your eggs every day if you'd like, after day 3 you should see something. * Be sure your hands are clean and dry. Oil from your fingers can clog the pores in the egg shell and keep the embryo from getting the oxygen it needs. * At about 8 days, you can see the peep wiggling and kicking in his egg.