Egg candling can be a most addictive experience. Years ago, when I first started home incubation, egg candling would begin on the third day, and then happened again nearly every day thereafter until lockdown. I couldn't get enough.
Secluded in a dark room with a very strong flashlight, I would imagine my pile of eggs developing and hatching into the most beautiful flock that would ever grace my part of the county. Witnessing the embryo jump and move through the shell during egg candling was almost as exciting as watching my own baby on the ultrasound machine when I was pregnant. My imagination would not cease until the babies finally hatched and were moved into their brooder... where yet another addiction would take over---chick watching---but that’s another story. THIS story is about the problems that arose for me when egg candling was done too often.
Here are five reasons why egg candling too often has caused problems for me:
1. I discarded viable eggs.
I’ve learned that there is really no reason for me to candle an egg prior to the 10th day. If egg candling happens any sooner than that, I might toss an egg that is growing just fine. If you’ve ever had that sickening feeling in the pit of your stomach after opening a "cull" egg just to find a beautiful little chick growing, then you’ll know where I’m coming from. I also candle a bunch of dark-shelled eggs. When egg candling it is wayyyy easy to miss a growing baby behind those mahogany shells. WHEN IN DOUBT, leave it in the ‘bator!
2. I detached fragile air cells.
Shipped eggs bring their own set of rules. Thousands of dollars and many eggs later, I've learned a few things... one of which is that I have far better results if egg candling doesn't happen right after they've been taken out of the box and unwrapped.
Now I simply give them a good visual inspection and allow them to rest. Resting means allowing the eggs to sit in the incubator for a few days, big end up, without the egg turner on. When egg candling happened too early, the extra handling, no matter how gentle I tried to be, often disturbed the fragile air cell. Now I just leave the darn things alone! You may think think that’s crazy talk, because conventional wisdom suggests egg candling right away to make sure there are no hairline cracks in the shells that can't be seen by the naked eye. All I can say is that leaving them alone rather than egg candling that early has increased my shipped egg hatch rate by quite a bit.
3. I contaminated my eggs.
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! Contaminated egg shells create dead chicks or an egg that could explode in the incubator! Which brings me to this: Even if you smell a bad egg, it is not necessary to candle. VERY carefully put each egg to your nose and take a whiff. You will smell a bad egg quite distinctly, and you can remove it from your hatch without having to candle.
4. I dropped fertile eggs.
It is always a sad day when I drop an egg, even if it’s just headed for the frying pan. Imagine how much more tragic it is when the egg is destined for hatching. But it gets worse: you can also drop and egg being candled onto the eggs below it! Talk about a dingbat moment, you should have seen me the day I decimated three eggs that were growing beautifully just because I dropped one during a sneeze (see Rule #3). I couldn’t have cried more if my dog died!
5. I lost heat and humidity in my incubator.
Back when I used a homemade and styrofoam incubator, it was always a very worrisome headache trying to keep the humidity and temperature just right. There were nights I would spend on the floor next to the eggs to try to regulate the heat properly in an uncooperative incubator that became unruly every time I had to open the lid to turn, much less candle. Adding an egg turner to your incubator, and candling less often, will reduce the number of times you'll have to fight this battle. (Bonus tip: Adding a little aquatic tubing so you can easily fill the water reserves will alleviate another reason to open the lid as well.)
Those are the five reasons I've reduced my egg candling.
So when DO I candle? Only twice, once at 10 days and again at 18 days. I candle at 10 days to cull the clears and the obvious quitters, and I can also perform the "sniff test" to detect if any are bad or rotten. Then I candle again at 18 days to cull any other quitters or bad eggs I might detect prior to lockdown. The next time I handle the eggs is when nothing can be hurt: during clean up, after the babies have hatched.
That's why I have "slowed my roll" on egg candling. Many people may disagree and candle more often, but I can only speak about what works for me. Now, I physically cringe when I read, “I’m on day three. I keep candling but I can’t tell if these eggs are fertile.” Yikes! Granted, that used to be me, but having hatched literally thousands of chicks at this point, I'm hoping that someone out there will read this post and learn from my egg candling mistakes so they can take advantage of my experience to improve their hatch rates!