Incubators work by surrounding the eggs in moist, warm air. There is a heat unit in the lid and you add water to wells in the base of the incubator. The eggs rest on a wire mesh tray.
My original Miller Little Giant Still Air incubator, the old school version that we got back in about 2003, still goin' strong! While the original thermometer is still in there just because, there is another, more accurate thermometer we added in the lid. The little hygrometer works just dandy.
The newer incubator, exact same model that we later added a forced air fan kit to so that is circulates the air better. Unfortunately this also makes holding humidity more difficult since it speeds evaporation. Fancier digital hygrometer/thermometer is JUST for reading humidity (thermometer isn't accurate enough). The blue thing is a child's toy called a Water Weasel--basically a plastic sleeve filled with liquid that is shaped like a doughnut. A digital thermometer is outside the incubator, it's probe goes in the doughnut hole of the Water Weasel. This slick arrangement gives you a MUCH more accurate reading of what the temperature is inside an egg, which is what you want--makes for a better hatch!
You need to maintain a temperature of 99.5 degrees and a humidity level of 50% for the first 18 days, and 65% the last three. I've split up the 56 eggs equally so that 28 are in each incubator, the various breeds equally divided to kinda hedge our bets a bit in case anything goes wrong during incubation...and there are only about 900 things that CAN go wrong during incubation!
The eggs will get turned, by hand, three times a day for the next 18 days. During that time we'll top off the water in the wells as needed, usually every three days or so. The eggs are marked with an 'X' on one side and an 'O' on the other so you can tell which ones have been turned at each turn. The eggs are marked for breed, we've also numbered them so people can choose their egg to cheer on during the Chickam web broadcast of the hatch. :) We'll candle the eggs (shine a bright light through each one in a darkened room) to check for development of the embryo at around 10-12 days into incubation and remove any eggs that haven't developed. On day 19 you top off the water in the wells, close up the incubators and wait for the next three days...this sends a signal to the chicks that it's time to hatch, and they rotate into hatching position.
If all goes well, on day 21 you see eggs rocking back and forth and hear the chicks peeping just before they begin to hatch!