Hatching chicken eggs in an incubator (or under a hen) is very simple, as long as you follow a few basic guidelines. While it may seem to be a very easy process, small variations in egg handling, temperature or humidity can cause your eggs to not hatch, or to not hatch into healthy chicks. Follow these simple DO's and DON'Ts to achieve the best hatch rate possible.
What happens before you even start to incubate the eggs can be just as important as your incubator temperature and humidity. So for an optimal hatch rate...
-DO choose the freshest eggs you can. Eggs retain good fertility for about 7-10 days, then it drops dramatically. You can collect eggs for about a week and then set them, but I wouldn't wait longer than that to pop them in the incubator.
-DO choose the most 'normal' eggs to set. Pass on any overly large or very small eggs, or those that are misshapen or otherwise 'wonky'. Small pullet eggs often don't allow enough space inside for the chick to develop, large eggs are often double yolkers - meaning two chicks could develop. Sometimes they both make it, but often, again there's just not enough room inside the shell for both chicks to develop correctly.
-DO choose the cleanest eggs you can. Washing hatching eggs is not recommended because each egg is coated with the natural 'bloom' which works to keep air and bacteria out - very important when you're hatching eggs. If need be, flick any dirt or poop spots off with your fingernail or a rough cloth, but remember that any dirt on the eggs will introduce bacteria to your incubator.
-DO store eggs with the pointy end down at a 45 degree angle. While you're collecting eggs to hatch, store them this way so that the yolk remains centered within the shell. Turning the stored eggs a few times a day side to side can also help your hatch rate, because that prevents the yolk from sticking to the shell.
-DO store eggs in a cool place around 60 degrees. Refrigerating hatching eggs can cause them not to hatch, and storing them in a warm place can cause them to start to develop, so keep them nice and cool until ready to set them, maybe the garage or basement.
-DO let the eggs come to room temperature and preheat your incubator before starting. Putting cold eggs into a hot incubator can cause condensation to form on the outside of the eggshell, which you want to avoid because that not only removes the bloom but increases the humidity inside the incubator. So let the eggs warm up a bit before setting them.
-DO candle the eggs before setting them. Discard any eggs with any hairline cracks in them. Or you can try to seal small cracks with melted beeswax.
-DO set your incubator out of direct sunlight. Overheating for just a few minutes can kill the embryos, so locate your incubator in a room where it isn't directly in front of a window.
-DO put the incubator out of reach of pets or children and teach kids not to touch the eggs or the incubator. Obviously eggs break easily, so they shouldn't be handled during the incubation period except to candle them (I usually candle on days 4, 7 and 18) but also each time the incubator is opened, the temperature drops, so you want to avoid unnecessary handling of the eggs and the incubator settings shouldn't be fiddled with either.
-DO remove any eggs that start to 'weep', turn black or smell. That indicates that bacteria has gotten inside the shell, and contaminated eggs sometimes explode, ruining the other eggs. (Evidence of a 'blood' ring, literally a reddish circle inside the egg when you candle, is also evidence of bacterial contamination.)
Follow these simple tips and your hatch should go off without a hitch. As for temperature, egg positioning and humidity in the incubator, follow the instructions for your specific model. For a detailed day-by-day hatch tutorial using my Brinsea Mini Advance, read HERE.
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