It is very tempting to candle eggs many times during incubation. There is nothing more exciting than seeing the developing chick! However, It is wise to remember that every time you candle the eggs, you cool them off. You also disrupt the temperature and humidity of the incubator. The more times they are subjected to this cooling, the more chances you have of disrupting the growth of the embryo and having a poor hatch.

We candle the eggs only twice, once before we place them in the incubator, to check for minute cracks, and proper air cell placement, and then finally, before placing them in the hatcher on day 18. This last candling is to check for any embryos that have stopped developing, or for any eggs that are infertile. These are removed and only potentially viable eggs are placed in the hatcher.

We have found that the easiest way to candle eggs is to take the entire tray out of the incubator, place it gently on the ground, turn off all the lights, and shine a small led flashlight that has a cardboard tube taped to the front of it (tubes from toilet paper rolls work well) right through the round top of the egg, while it remains in the tray. By day 18, what you will see is a distinct clear air cell on top, and a dark mass underneath. These are the eggs you need to place in the hatcher. Any that have large clear areas should be discarded, as this indicates quitters during incubation. It only takes a few minutes to candle many dozens of eggs this way.

IMPORTANT NOTE: If you absolutely must candle half way through incubation, don't be confused by the large clear area on the bottom (pointy end) of the egg. This is not the air cell. This is just the remaining liquid that the embryo has yet to utilize. I have had many a panicked call asking why all the air cells were on the bottom!

The best rule of thumb to have a great hatch, is to curb your enthusiasm and curiosity, and to limit candling to a bare minimum. If you want to see eggs developing, there is always the internet and its many videos showing just this miracle!