I first purchased a styrofoam still air incubator a couple of years ago and have hatched several clutches in them since. My experiences is with chicken eggs, so all reference in this blog to eggs will be referring to chicken eggs. There basically two types of incubators still air and forced air. There are countless styles of each one of these. The ones that I am most familiar with in a styrofoam box with the heating element in the top. The incubator has a thermostat with the control on the top. I have also purchased the automatic turner that goes along with the incubator and this is a good item to have.
Placement of the incubator in the house or area you are going to operate it is very important. It will temperature fluctuations if is near a window, door, in direct sunlight, or near a draft. The incubator needs to be in a room with a fairly stable temperature. I also put a couple different thermometers in mine usually one that I know is high quality and the other for a back up.
Place the auto turner inside of the incubator and plug both the incubator and turner up. I remove one of the vent plugs at this time. I do not put eggs i yet. I check the temperatures ever hour and adjust as needed we are trying to get as close to 101.5 as possible with a still air model. I usually leave mine overnight with the temperature adjusted. After a good warm up period place the eggs in the turner and then put the lid back on the incubator. Check the temperature every hour again because the temperature will change once the eggs are placed in the incubator.
As far as humidity is concerned, there is two ways to do this and I have tried both. The first one is to keep a small amount of water in the incubator the entire time and increase it at lockdown (which we will cover later). The second method often referred to as the dry hatch method. This is to not add any water to the incubator until lockdown. I have tried both methods and have had luck with both. The last few hatches I have used the dry method.
It takes twenty one days, give or take a day or two, for chicken eggs to hatch. During this time, keep an eye on the temperature. I also candle my eggs at ten days and then again at lockdown. Candling consists of shining a light into the egg. I use a led light in a totally dark room with my hand cupped so no light excapes. I discard any that are clear, have blood rings, are not developing, or have a smell.
The last three days of the incubation is referred to as lockdown. I put my incubators in lockdown on day eighteen. I remove the auto turner with the eggs in it. I then fill the trays in the bottom with distilled water, at this point I try to get the humidity in my incubator to stay around 60-65%. A hydrometer will check the humidity levels. This is referred to as lockdown because you do not want to open your incubator at all during this time. Hatched chicks do not need food or water for the first couple of days because of the yolk sack they absorbed.
In closing, hatching chicks is an enjoyable experience. It is also an edjucational one. Watch your placement of the incubator, temperatures, and humidity. When obtaining fertile eggs, try to get eggs from young, healthy parent stock.