As to incubators, we had forced air Hovabators. Hovabators (and the Little Giant incubators) are the dickens to keep at the right temperature. They are also very had to disinfect. Sometimes you can have 100% hatches and sometimes nothing hatches. The main advantage of these Styrofoam incubators is their price. I highly recommend the forced air model. The egg turner is convenient but not necessary, you can do very well turning eggs by hand twice a day. There is a new Hovabator with an electronic temperature control. I have not used this model.
We now have a GQF Sportsman with electronic thermostat. I got tired of adjusting the wafer thermostat twice a day. The Sportsman has a hatching tray. We are very happy with the Sportsman except we have nowhere to increase the humidity to hatch without making the humidity too high for the just set eggs.
The Dickey incubator is almost identical to the Sportsman but has a wooden cabinet instead of pressed board.
I'm still in search of the perfect incubator. In my mind it has half the capacity and price of a Sportsman. This will allow me to buy one for setting and one for hatching.
Forced air is the only way to go; it gives a uniform temperature inside the incubator. The fan should be on all the time not just when the heat is on.
Wafer thermostats change set point when the atmospheric pressure changes. I strongly recommend electronic temperature control. I do not recommend the electronic control on the Little Giant because the temperature wandered too much and too often.
Wafer thermostats and the electronic thermostat in my GQF Sportsman change set point when the inside humidity changes (for example when the humidity pan dries out).
Wafer (and I assume electronic) thermostats change set point when the room they are in changes temperature.
It is important to put your incubator is a place where the temperature and humidity are constant and there is no breeze. The temperature controllers will not work in rooms where the temperature changes.
The temperature should be 99.5 degrees Fahrenheit for chicken eggs.
You must measure the temperature, but no matter which thermometer you use, adjust the temperature according to when the chicks hatch. Chicks are the best indicators of temperature. Increase the temperature if they hatch late, decrease if early.
Do not adjust the temperature if the humidity is wrong. The thermostat keeps a different temperature when the humidity changes. This means you must watch the temperature after you increase the humidity 3 days before hatch.
We use the small GQF electronic egg thermometer. It is accurate to +/-0.18 Fahrenheit degrees. Many larger digital thermometers and thermometers/hydrometers are only accurate to +/-1.8 Fahrenheit degrees. Since this is exactly a factor of ten and catalogs are printed on newsprint, you have to read the catalog very carefully. We like the larger thermometer/hydrometer for measuring humidity.
Another benefit of the GQF digital thermometer is it responds quickly to temperature changes. To control a Hovabator we averaged the minimum temperature (when the heat turns on) and the maximum temperature (when the heat turns off). The thermometer/hydrometer takes tens of minutes to settle to the inside temperature. Make sure you place the probe of the thermometer at the height of an egg's top, just where the Hovabator manual shows.
The humidity should be 50% days 0-18 and 65% days 19-21.
You must measure the humidity. I like the inexpensive combination humidity and temperature gauges one can buy at most hardware stores and stores like Wal-Mart. Do not use this device for measuring temperature! It is very inaccurate and responds too slowly to changes in temperature.
High humidity prevents moisture from leaving eggs and the chicks drown. Low humidity at hatching gives stuck chicks and chicks that don't hatch at all. The membrane inside the shell gets tough and the chicks can't poke through. Even if they pip, many stick to the membrane and either can't get out or get deformed feet, beaks, and I assume other parts too.
Nathalie (ThreeHorses) calls the last three days of incubation "Hands-Off Days". These days are most important to the hatch. Opening the incubator quickly drops both the temperature and the humidity. Nathalie suggests putting an aquarium tube through the incubator vent into the water troughs. Then you can add water without opening the incubator.
Chicken eggs take 21 days from the time they are put in the incubator. Do not start counting days from when the eggs are laid. Do not start opening eggs until 2 or 3 days after they are due. Wait even if most of your eggs hatched. If the temperature is low or if that unhatched egg was in a cooler spot of the incubator, that egg might just hatch late.
We were happily hatching with the Hovabator with me adjusting the temperature twice a day. Then the Styrofoam got bacteria in it. I always scrubbed the Styrofoam and submerged it in bleach solution for an hour. To clear up the infection, I soaked in bleach solution for 24 hours and left it in direct sun for a day.
I hear there are now inserts for the Hovabator bottoms. These should make disinfecting much easier.