Science of Incubation
Incubation means maintaining conditions favorable for developing and hatching fertile eggs. Still-air incubators do not provide mechanical circulation of air. Forced-air incubators are equipped with electric fans. Optimum operating temperatures differ slightly.
Four factors are of major importance in incubating eggs artificially: temperature, humidity, ventilation and turning. Of these factors, temperature is the most critical. However, humidity tends to be overlooked and causes many of the hatching problems encountered by teachers. Extensive research has shown that the optimum incubator temperature is 100°F when relative humidity is 60 percent, concentrations of oxygen 21 percent, carbon dioxide 0.5 percent, and air movement past the egg is at 12 cubic feet per minute.
An incubator should be operated in a location free from drafts and direct sunlight. An incubator should also be operated for several hours with water placed in a pan to stabilize its internal atmosphere before fertile eggs are set.
The relative humidity of the air within an incubator for the first 18 days should be able 60 percent. During the last 3 days (the hatching period) the relative humidity should be nearer 65-70 percent.
Turning the eggs during the incubation period prevents the blastoderm from migrating through the albumen and sticking to the shell membrane.