Candling chicken eggs is an exciting part of the incubating process. I don’t always candle them, but I usually do.
Candling the egg gives you a glimpse at what’s happening inside.
When I use an incubator to hatch eggs, I typically candle them a couple times within the 21 developing days. I don’t bother candling them until at least day 4 because I can’t see anything before then. And, I don’t candle after day 18 because the eggs are in lock down.
Most often if a broody hen is sitting on eggs I don’t candle them. I leave the broody to tend her eggs. The exception is if I think her eggs aren’t good. Before taking them away I will candle them.
MY CANDLING METHOD
My incubators came with candling tools, so I use those. But, I’ve also had success with a flashlight. I go in a dark room, hold the candling tool to the egg, and inspect the egg.
The first couple days there is little to see when candling. Usually on days 3 or 4 is when the veins just become visible. By day 6 those veins should really be easy to see.
The embryo starts to grow & fill its shell, but still has room to wiggle around. Often you can see the shadow of the embryo moving inside the shell. It’s absolutely great to see.
Days 15 – 18 the chick is filling most of the egg. When candling, nearly the entire egg is black except where the air cell is.
Do not candle the eggs past Day 18, as they need to be in lock down and not disturbed.
EGGS THAT AREN’T DEVELOPING CORRECTLY
Sometimes the eggs don’t develop into a hatched chick.
Left: This egg is clear – meaning it never started developing. It’s possible that it was never fertilized. If I think an egg is clear, I leave it in the incubator and check it again a couple days later. If it’s still clear, I take it out.
Right: This egg has a blood ring. For some reason, the embryo started developing, then quit. This one gets taken out of the incubator.
Some hatches I candle more than is recommended. Some hatches I candle 2 or 3 times & some hatches don’t get candled at all.
It is recommended to candle only 2 or 3 times within the 21 day period. That really is all that is necessary to check the development of the eggs. But, some hatches I’m more antsy and curious about what’s going on. So, I candle more often. Hands-on experience is how I learn best. Candling more versus candling less, hasn’t changed my hatch rate. Although, I could see how messing with the eggs more than necessary could be a bad idea. So, please use your best judgement when deciding how often to candle your eggs.