When incubating eggs, or when a hen is sitting on a clutch, there is a way to find out whether or not a chick is actually growing in there. This process is called candling.
Long ago, it was actually done using candles, but nowadays there are many different ways to do it. You can buy special egg candling equipment, or simply rig something yourself.
The idea is to shine a very bright light through the eggshell in a dark room, which illuminates the shell, and allows you to see what’s going on inside!
How Does Candling Work?
Candling works by shining a bright light source behind the egg to notice the growth and development of the embryo inside.
This way you can see through the transparent shell and view details inside, including veins, shadows on the eggshell, which can indicate the fertility and developmental stage of the egg. As the embryo grows, these details become more pronounced and visible in stages, allowing you to notice the progress of the fertilized eggs.
Why Should You Candle Eggs?
Candling is crucial for determining which fertilized eggs are developing and which ones might have problems. Candling provides valuable insights that can inform your estimates on hatching rates and help prevent potential issues with bad eggs in the incubator.
By candling your eggs, you can tell the difference between viable and non-viable eggs, make informed decisions about which eggs to continue incubating, which to ditch, and what the probable issues with them are, if any.
Spotting “yolkers” (eggs that were never fertilized to start with), and “early and late quitters” (eggs that stop developing) among your incubating eggs will prevent major problems (like exploding rotten eggs!) and give you a better idea of how many chickens to expect from a clutch.
Candling will always contribute to a more successful hatching process and better flock management overall!
Is Candling Harmful to the Egg or Chick Inside?
No, not usually, as long as you do it right! Candling doesn’t affect the egg or chick inside as long as you minimize the time the eggs are out of the incubator and avoid candling them too often.
Remember that incubating eggs must have the right temperature and humidity levels in order to develop properly and with certainty. Being out of the incubator environment, with its ideal temp and moisture levels, for even a short time can have serious consequences.
Also, care must be taken to avoid getting an egg too hot. Many light sources like flashlights and even certain egg candlers get quite warm when they are left on, and leaving the egg in contact with them or in close proximity can dangerously overheat them.
Additionally, special care should be taken to protect the eggs from contamination during the candling process to ensure the health and safety of the developing embryos.
When Should You Candle an Egg?
You should candle an egg either 6 or 7 days after laying to verify development or at about 14 days in the incubator to check for proper development prior to hatching. However, it’s crucial to avoid candling the eggs repeatedly or too often, as this can potentially cause developmental issues.
Taking an egg in and out of its incubation environment repeatedly, or moving it around too much, is likely to cause significant problems, and remember that every time you touch it there is a risk of contamination which could cause it to fail.
Check your eggs at the right time and only when necessary, and they’ll be fine.
What Are You Looking For When Candling?
When candling chicken eggs, you should look for the presence of “veins” and “blobs,” which signify the development of the chick inside the egg. This visual inspection allows you to both verify and monitor the growth and progress of the tiny little embryo inside.
The veins are a network of blood vessels that are basically invisible for the first couple of days after laying, but will quickly become prominent and easy to see if your light source is bright enough.
Also, later on in development, you want to check for the presence of the air sac, indicated by a slightly darker patch in the lighter, transparent area near the bottom of the shell.
As the embryo grows and develops, it will take up more room and turn the eggshell opaque or shadowed once again. This is normal.
Additionally, especially in the early stages, you should be vigilant for otherwise invisible cracks, as these could indicate potential issues that may affect the viability of the egg.
Do You Need Special Equipment to Candle Eggs?
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No, you can candle eggs with nothing more than a flashlight or your smartphone (if it has a light), but using specialized equipment such as an egg candler can make the job quicker, easier, and safer.
An egg candler is a specialized device designed for candling eggs, typically consisting of a strong light source and a holder to secure the egg for inspection while preventing light “leakage” around it. Good ones also have turntables that let you to smoothly and safely rotate the egg when under observation without directly touching it.
Whatever the type, this tool provides better visibility and stability, enhancing the candling process and allowing for more accurate observations.
Wash Your Hands!
Why wash your hands in the first place? Aren’t egg shells impermeable and protecting the embryos inside from infection?
Well, as it turns out eggs are very susceptible to contamination from bacteria and other microorganisms. These unwanted “guests” can easily transfer from your hands onto the eggshell before migrating inside and then potentially harm the developing chick inside.
Sound impossible? It isn’t: eggshells are permeable! And germs aren’t the only threat. Chemicals on your hands, even something like ink, could spell disaster for the poor incubating embryos.
Washing your hands thoroughly with soap and warm water ensures that you’re not introducing any harmful elements to the precious and incredibly fragile life growing within the eggs.
So always remember, cleanliness first! Wash up before you handle and candle; it’s a simple step but vitally important for healthy chick development.
My Experience Candling
Tonight, we candled our 15 eggs. What we used was very basic- a desk lamp and a small box. In the top of the box we cut a hole, just big enough that the egg could barely sit down in it without falling through.
We laid the lamp down on a table, and put the box over the light bulb. With all other lights off, we put each egg, one by one, over the light shining through the hole in the box.
You guys, this is so exciting! It’s almost as good as seeing a sonogram! The light shined through the eggshell, and we saw a little chick growing (and moving) inside! I squealed with excitement when I saw that first little chick moving within its shell.
After 72 hours of incubating, we could easily distinguish between fertile and non-fertile eggs. The good ones had spider-like blood vessels spreading within (see picture above).
For the eggs that were obviously not fertile, we put them on the menu for dinner: they are still safe to eat after being incubated for up to nine days.
I wish we would have candled some of our eggs sooner, though. Some of ours have been incubating for two weeks now, so the chicks are quite developed. Once the chicks are so far along, they appear to be a large dark mass within the shell.
Some of mine moved, so it was easy to tell that a chick was alive in there. But others just looked like an impenetrable dark shadow. I’ve had a very hard time distinguishing between good eggs and bad ones at this stage.
It wouldn’t be such a big deal to just leave them alone and not worry, but the bad ones can rot and actually explode- spreading bad bacteria all over the other eggs, and making a big, stinky mess in the incubator!! So I definitely want to get the infertile ones out.
There are some eggs that I think are bad, but dang, I’d hate to throw one out if it’s actually alive!! I’m gonna have to candle them again and really take a close look to determine whether they are in fact growing or not.
A city girl learning to homestead on an acre of land in the country. Wife and homeschooling mother of four. Enjoying life, and everything that has to do with self sufficient living.