Initially the egg will look clear, apart from the air cell which you may be able see at the 'fat' end of the egg – but probably not before day 4 or 5. As time goes by you'll notice this air sack become larger. It's here that the
Eggs must be turned at least 4-6 times daily during the incubation period. Do not turn eggs during the last three days before hatching. The embryos are moving into hatching position and need no turning. Keep the incubator closed during hatching to maintain proper temperature and humidity.
If chick embryos develop to the pipping stage, or at first shell cracking at hatching, they are normally healthy enough to hatch unless some incubator adjustment prevents it from happening. The problem is usually caused by either 1) poor ventilation or 2) improper humidity.
The day before the hatch you should prepare their brooder to receive the chicks. On day 21 you will begin to hear peeping from the inside of the eggs. Some of the eggs will likely begin to rock around a bit as the chick “pips” the shell.
Listen: Take an egg from the refrigerator and hold it up to your ear. Shake it gently. If it's fresh, it won't make a sound. If it's on the older side, the egg will make a slight rattle.
Eggs are porous, so moisture is lost from inside the egg during incubation—the size of the air sac increases, and the weight of the egg decreases.
Ventilation is very important during the incubation process. While the embryo is developing, oxygen enters the egg through the shell and carbon dioxide escapes in the same manner. As the chicks hatch, they require an increased supply of fresh oxygen.
You'll see blood pumping through the heart of a tiny, developing embryo if you candle a fertile egg on Day 4. If the embryo dies at this point, you may still see a faint network of blood vessels inside the egg's contents. An embryo dying at this point will show a large, black eye.
If there are still unhatched eggs at day 21, don't despair. It is possible that timing or temperature went slightly awry, so give the eggs until Day 23. Candle any unhatched eggs to see if they are still alive before discarding them. Keep in mind that when hatching eggs, you will likely end up with roosters.
On day 20, the chick pierces the membrane into the air chamber. The chick breathes air for the first time, and you may hear the chick peeping inside the egg. This is called pipping. On the 21st day, the chick begins to break out of the shell.
As long as you don't keep it chilled for too long, answer is: No, it usually just slows down the development of the embryo, so it is possible to slightly adjust the "birthday" of the chick by adjusting the temperature.
Below about 27°C (80°F) no embryonic development takes place. Prior to incubation, eggs must be stored in this temperature range, ideally around 15°C/59°F. Below this threshold ice crystals will start to form in the egg and permanently damage may be done to internal structures meaning the egg cannot hatch.
Do all chicken eggs take the same time to hatch? No. Various things will influence hatch times: the age of the eggs, the health of the mother hen, fluctuations in the incubator temperature... Sometimes chicks hatch a little before 21 days, sometimes it can be several days after.
Temperature too low and rela- tive humidity too high during incubation period. Check thermometer; 1ºF (0.6ºC) below 99.5ºF (37.5ºC) will cause late hatch. Old eggs. Set only fresh eggs; allow extra time for hatch by setting old eggs early.
Transferring to the hatcher should not occur after 19 days (456 hours) of incubation, because disturbing the eggs at this time adversely affects the act of internal pipping.
Dead embryos will typically look like a murky, dark shadow. Unfortunately, any eggs containing blood rings are not viable. Any clear eggs or eggs containing blood rings should be removed from the incubator at this point to avoid any rotting.
Spraying of water in an incubator creates local cooling, as the eggs that are close to the sprayer will lose more heat to facilitate the evaporation then the eggs further away.
Wet or Dry Hatch? Humidity can be a bigger problem. Many experts believe that 'dry hatching' is the best way to go. The theory is that many chicks drown in the shell because the air cell is not big enough.
Results from this study indicate that properly washed clean or dirty eggs hatch as well as unwashed eggs.
Incubation Reminders
Place the incubator in a room with a constant temperature, no drafts or direct sunlight. Sanitize the incubator. Wash hands before touching eggs.
Hold an egg by your ear and shake it. If you hear nothing, then many say your egg is OK, based on anecdotal evidence. If you hear liquid sloshing around, it means the yolk and/or white have deteriorated and are no longer fresh and firm but rather old and watery.
Then, thanks to Google, we realized that it's actually common or normal for eggs to make a “chirping” sound when there is any air escaping from the eggs while they are boiling.
A larger air pocket gives the egg more room to move around inside the shell and create a sloshing sound. A fresh egg should not make much, if any, sound when you shake it. A sloshing egg only indicates that the egg is old and does not mean the egg is unsafe for consumption.