Oldest incubator from Holland ca 1896
After testing the incubator it's important to keep the chicken eggs in a controlled environment for 21 days to be sure of an healthy hatch. The temperatur, humidity and ventilation have to be stricktly controlled.
The eggs need to be turned twice a day every 12 hours; this is to help the chick embryo to develop into a healthy chick during the incubation period. To control the environment keep the incubator in a room free from drafts and where the room temperature remains as constant as possible. Placing the incubator near an window, heater or vent could cause to fluctionsions inside the incubator.
Setup the incubator up to a working temperature of 102°F. The water reservoir should be filled with warm water and the thermometer set in place. Once the temperature has stabilized, allow any stored eggs to warm gradually to room temperature before putting them in the incubator. Eggs sweat if warmed too rapidly, providing another chance for bacteria to enter the shell.
Maintain the temperature in the 99-102° F. temperature range (100-101° F., if possible). Place the thermometer to measure the temperature at a level at or slightly above where the center of the egg will be. Overheating the embryo is much more damaging than is underheating it; overheating speeds up embryo development, lowers the percentage of hatchability, and causes abnormal embryos. Although a short cooling period may not be harmful, longer periods of low temperatures will reduce the rate of embryo development. Excessively low temperatures will kill the embryos. Avoid temperatures outside the 97-103° F. range. If the temperature remains beyond either extreme for several days, hatchability may be severely reduced.
The moisture level in the incubator should be about 50 to 55 percent relative humidity, with an increase to about 65 percent for the last 3 days of incubation. Moisture is provided by a pan of water under the egg tray. The water surface should be at least half as large as the surface of the egg tray. Add warm water to the pan as necessary. If more humidity is needed, increase the size of the pan or add a wet sponge. Humidity adjustment can also be made by increasing or decreasing ventilation.
Ventilation is crucial because the embryo is a living organism which exchanges oxygen and carbon dioxide through the shell during the incubation process. The amount of air exchange needed increases as the embryo develops. The vents, which are located above and below the eggs, should be opened gradually until they are fully open the final three days of incubation. Ventilation rates that are too low prevent normal moisture evaporation and cause large weak chicks or death. High ventilation rates remove too much moisture and can cause the shell to stick to the chick, making hatching difficult.
Humidity is also important because of the egg’s porosity. Keeping adequate humidity in the incubator will help insure that no more moisture than necessary is lost by the developing embryo. Humidity should be adequate for the first 18 days of incubation if the water pan is kept full and covers an area greater than half the floor of the incubator. During the last three days of incubation, adding a large sponge inside the incubator should increase the surface area of water and give the necessary boost to humidity. Low humidity can cause the shell to stick to chicks, rough navels, small chicks, short down, and/or death. High humidity can cause an unabsorbed yolk sac, resulting in the chicks being smeared with yolk.
The relative humidity inside the incubator should be between 50 percent and 55 percent during the first 18 days and between 60 percent and 65 percent during the remainder of the incubation period.