What is candling eggs?
Candling an egg is the process of shining a bright light through the egg to see the contents without breaking the shell. It is used to see whether the egg is fertile or not and to check on the development of the embryo.
Candling will also tell you that the air sack has increased to the correct size for a smooth hatch. Eggs lose water weight during incubation and the air cell get bigger. Candling is a good way of checking the humidity is right in the incubator.
Using a bright light is a cheap, simple and quick way of making sure the eggs are incubating as they should be.
Below: What you should see when you candle a fertile egg.
What do fertile eggs look like when being candled?
When you first candle an egg the inside looks like a spidery network of blood vessels around the embryo in the middle.
Care and precautions when candling eggs:
- Have clean dry hands. Oils and bacteria on your hands could contaminate the eggs.
- Have your equipment set up before you start candling.
- Do not candle to early or late in the incubation cycle. The embryo is very susceptible to damage in the first few days and you may disturb the hatching process at the end of the cycle.
- Work quickly so as not to allow the eggs to chill but do not rush.
- Don't leave the eggs against a hot lamp for too long.
- Don't candle too often
How to hold eggs while candling:
Grip the egg firmly between your fingers with the thumb on one side and the other fingers making a sort of cage and either put the candling lamp to the bottom of the egg or place it gently on the table based candling lamp.
Can you candle eggs too often?
Yes, you should limit the amount you candle eggs, the more you mess around with your eggs the greater the likely hood you will drop them, damage the eggs in some way, drop them or allow them to get cold.
Using an iPhone or mobile phone to candle eggs:
Most mobile phone covers have a handy little indentation just where the light and camera is that an egg will fit into quite happily.
Below: A smartphone being used to candle chicken eggs.
Put your phone face down on a soft cloth with the light on and place or hold the egg over the light. iPhone and mobile phone lamps are bright enough to candle most eggs quite happily.
Can you use a flashlight to candle eggs?
Yes with no problems at all. Most candling lamps are modified torches with a rubber bung on the end to seal flush with the egg and stop light leaking out.
What are the limitations of candling eggs:
You will not be able to tell the sex of the chicks in the eggs.
Exactly how much you can see is limited to a blob and spidery veins.
Eggs from birds like Black Copper Marans, Barnevelders or Welsummers are very dark shelled and as such are incredibly difficult to see into because of the shell pigment. These types of eggs need a lot of practice and a very bright lamp to see what is going on.
Blue, olive coloured or green eggs can also be problematic as the pigment goes all the way through the shell.
Candling won't tell you exactly when hatch day is.
What is the best candling lamp to use?
I use a a brinsea Ovaview candling lamp. It has a strudy base, bright LED light and a rubber ring to ensure a good seal with the egg. Mine has given me years of good service and the batteries last a good while.
Below: My Brinsea Ovaview candling lamp in operation.
Light emitting diode lamp illumination rather than standard bulbs and avoids potential for overheating eggs during inspection and it is more efficient than incandescent bulbs.
Where to get candling lamps:
You can buy a variety of candling lamps in:
- Pet shops.
- Online - Use the Amazon link above and we get a small affiliate commission to help with the running of the site.
- Animal feed merchants
- Specialist stores.
You can just as easily use a torch or mobile phone light.
How to candle eating eggs:
Candle eggs you are going to eat to look for blood spots is very difficult and requires a very bright light. This is actually done commercially to minimise the amount of foreign bodies inside the eggs.
Below: A worker picking eggs of the production line.
Interestingly this is still a job that has to be done by a human, machines can't see blood spots in eggs reliably.