Egg Incubation Info: FAQ's on Candling Eggs
FAQ's on Candling
1. Will all the eggs in my incubator hatch?
It is probable that only 90 percent or less of incubated eggs are fertile. (Not all 90% of eggs will hatch either).
Removal of eggs that can be identified as infertile or dead eliminates possible sources of contamination from the incubator.
Candling can be used to identify some of these eggs.
Shining a light through the egg to observe embryo development is called candling
White or pale eggs are more easily candled than dark or speckled eggs. Many people use small flashlights with lenses that can be focused to candle eggs.
Excellent candlers also can be purchased at a reasonable cost. Simple candling devices can be made by inserting a light into a container and cutting a small hole to emit light, or by taping a cone formed from several thicknesses of paper over the lens of a bright light projector. The hole that allows light to pass from the tip of the cone should be dependant upon the size of the egg.
In a dark room, hold the egg to the light of the candler to observe the contents of the egg. Cooling that occurs for short periods (less than 10 minutes) during careful examination of eggs does not harm the development of the embryo. However, limit the exposure of the egg to the hot light source.
The presence of embryos can be confirmed easily after 8 days to 12 days of incubation.
The embryo is located in the large end of the egg, where blood vessels radiate under the surface of the shell. The embryo appears as a dark spot that becomes larger as incubation progresses. Eventually only a dark mass and the air cell are seen. An infertile or unincubated egg brightly transmits light in comparison. Remove infertile or non-growing eggs from the incubator. If questions arise about candling, contact someone with experience for advice.
Dead embryos will sometimes appear as a ring or smear of blood in the egg or a dark spot dried to the inside of the shell. The living embryo will appear as a dark spot in the large end of the egg surrounded by a faint outline of blood vessels. The blood vessels will appear firm and distinct. After embryo death, the embryo no longer grows and the blood system fades.
Retain records of egg infertility or embryo death. Some mortality can be expected, however, unusual occurrences of mortality or certain characteristics of the mortality can be indicators of practices that can be corrected to improve hatchability.
2. How do I candle eggs?
Shine a bright light through the egg. Candling is not a specific art.
It is more of a comparison, meaning all the eggs of the same age should look the same. It is something best learned by doing it, and really is just as simple as you make it. You cannot hurt eggs by candling them (short of dropping them). They can be out of the incubator for a half-hour without any harm. Candle every day if you like, after day 3 you should see something. At about 8 days, you can see the chick wiggling and kicking in his egg.
3. How do I spot bad eggs?
The egg on the left shows a ring at 6 days. This ring is formed by concentrated bacteria which has invaded the eggs' membrane. It can become present very early, or after the chick has already started to form, as in the picture on the right. In the picture on the right the ring, or portion of it, can be seen at the bottom of the egg with the expired chick in the middle.
For a different reason. The egg on the left shows a blood spot. In my experience an egg with a blood spot will not hatch. They will go bad and blow up, though. The egg on the right at 6 days shows "clear". It is infertile, or too old to germinate.
The egg on the left shows a blood spot incubated to 8 days. You can see the bacterial ring forming at this point. Soon this egg will start to "weep", and if it isn't caught in time, it will explode into a stinky mess. The egg on the right shows highly defined pores. Eggs that look like this under candling have a slim chance of hatching in my experience. I've noticed that it mostly depends on the severity of the porosity.
On the left, you can see the "spider" of veins growing away from the peep. This egg is at 6 days. You can see this spider in a smaller version at 3 days. The egg on the right is at 2 weeks. You can see the clear spot beneath, with the yolk and peep floating at the top.
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