Research has shown that different eggs need to be turned in different ways. Some are best turned automatically by roller or trays which tilt them to a 45 degree angle while others need to be turned side to side by hand up to seven times a day.
It is very important that the temperature in an incubator does not fluctuate too greatly. Most eggs should be incubated at 37.3C with no more than half a degree fluctuation up or down.
Weight Loss and Humidity
Eggs lose weight as they develop. A fresh egg with a density greater than water will sink, while one nearer to hatching with a lower density will float.
By weighing eggs regularly, calculating density and using existing data it is possible to adjust an incubators humidity to the correct levels.
This is the technique of observing the egg development through the shell. It is a simple matter of shining a bright light through a hole in front of which an egg is placed.
This is by no means a speedy process and can take up to four days. The first stage is known as the internal pip. This is when the chick breaks through the inner membrane into the air space inside the egg. At this point eggs should be moved into a separate incubator. This is necessary as eggs can release bacteria which would infect eggs still being incubated.
The hatching incubator has a temperature 1 degree lower than normal since the chicks are already producing their own body heat. It also has a humidity as high as is possible, which helps the chicks break through the shell. It will take the chick a day to pip, that is breaking the first hole in the shell. After this, being able to breath easily, it will rest for one or two days before hatching out.