Preparing eggs for incubation starts well before you turn on the incubator. The steps you take during collection, storage, and setting directly determine how many eggs hatch and how healthy the chicks are. Most hatchability problems trace back to poor handling in this window, not to the incubation itself. Here’s how to get it right from the moment you collect your fertile eggs.
Selecting the Right Eggs
Not every fertile egg is worth incubating. Start by choosing eggs that are average-sized for the breed. Unusually small or oversized eggs hatch at lower rates and can produce weaker chicks. Eggs from very young hens tend to have proportionally less yolk, which means less nutrition for the developing embryo. If your flock is under 30 weeks old, expect slightly lower hatch rates.
Look at the shell itself. You want smooth, evenly textured shells with no ridges, bumps, or thin spots. Reject eggs with visible cracks, and be aware that hairline fractures, ones too fine to see with the naked eye, are a serious problem. These nearly invisible cracks lead to more than three times the embryo loss compared to intact eggs. Candling each egg with a bright light before storage helps you catch these fractures, along with other disqualifiers like a detached or misshapen air cell. When you candle, you should see a small, stable air cell at the wide end of the egg. If the air cell moves freely when you tilt the egg, that membrane has detached, and the egg is unlikely to hatch.
Also reject any eggs with an unusual shape: overly round, elongated, or lopsided eggs don’t incubate well. Stick with clean, well-formed eggs of normal size, and you’ll eliminate a surprising number of potential failures before incubation even begins.
Cleaning Without Damaging the Shell
Fertile eggs have a natural protective coating called the bloom (or cuticle) that seals the shell’s pores against bacteria. Washing eggs with water strips this coating and can actually push bacteria through the pores into the egg, so avoid washing whenever possible. The best approach is to collect eggs frequently, at least twice a day, to keep them from getting dirty in the first place. Keep nesting boxes clean with fresh bedding, and discard any eggs that are heavily soiled.
For eggs with minor surface dirt, dry cleaning works well. Lightly sand or buff the soiled spot with fine-grit sandpaper or a dry abrasive pad. If you feel you must sanitize, commercial hatcheries spray eggs with sanitizing solutions and let them air-dry for about 30 minutes at room temperature. Small-scale options that have been tested as alternatives to industrial fumigation include spraying with grain alcohol or diluted essential oil solutions. The key principle is to sanitize the surface without soaking the egg. Never submerge hatching eggs in water.
Storage Temperature and Humidity
Once collected, fertile eggs need to be held at cooler temperatures that pause embryonic development without killing the embryo. For storage of up to one week, keep eggs between 55°F and 68°F (13°C to 20°C). Relative humidity should stay around 70 to 75% to prevent the eggs from losing too much moisture through the shell. Excessive moisture loss during storage creates the same problems as running your incubator too dry: large air cells, dehydrated embryos, and poor hatches.
If you need to store eggs longer than seven days, lower the temperature. Research shows that dropping to around 50 to 54°F (10 to 12°C) significantly improves hatch rates for eggs stored 9 to 14 days compared to holding them at standard temperatures. A basement, wine cooler, or cool spare room can work if you monitor conditions with a thermometer and hygrometer. To boost humidity in a dry storage space, place a shallow pan of water nearby or drape a damp towel over the egg container.
How Long You Can Store Eggs
Hatchability holds steady when eggs are stored for seven days or fewer. After that, every additional day of storage chips away at your hatch rate. Eggs stored for 10 days show measurably higher embryo mortality than those stored for just three days, and storage time has been identified as the single most important factor in early embryonic death, outweighing genetics, hen age, and incubator type.
For the best results, aim to set your eggs within three to five days of collection. If you’re gathering eggs over several days to fill an incubator, start counting from the day the first egg was collected. Going past 10 to 14 days of storage, even under ideal conditions, means a meaningful drop in the number of chicks you’ll hatch. Plan your incubation schedule around this window.
Positioning and Turning During Storage
Store eggs either on their sides on a soft surface like a towel, or upright with the wide (blunt) end facing up. Never store eggs with the pointed end up, because the air cell sits at the wide end and needs to stay in position. If you’re using an egg carton or tray, make sure the fat end is at the top.
Turning eggs during storage prevents the yolk from settling against the shell membrane and sticking, which damages the embryo. Tilt eggs about 45 degrees from one side to the other once a day. A simple way to do this is to prop one end of the egg tray on a book or block, then move the block to the opposite end the next day. This gentle rocking keeps the yolk centered and the embryo viable throughout the storage period.
Preparing the Incubator
Before your eggs go in, the incubator needs to be clean and stable. Wash all removable parts with warm soapy water and disinfect interior surfaces. A quaternary ammonium disinfectant works well for this, and products like Lysol No Rinse are widely available. You can also wipe surfaces down with 70% ethanol and let them air dry completely. Avoid spraying alcohol directly on temperature or humidity sensors. If your incubator has a water pan, clean it thoroughly and fill it with fresh water.
After cleaning, run the incubator empty for at least 24 hours. This lets you verify that temperature and humidity are holding steady at your target settings (typically around 99.5°F for a forced-air incubator or 101 to 102°F for a still-air model). Use a separate thermometer and hygrometer to double-check the built-in readings, since even small calibration errors can ruin a hatch. Adjust ventilation so there’s gentle airflow without drafts. Only once conditions are rock-solid should you add your eggs.
Warming Eggs Before Setting
Moving cold eggs straight from storage into a warm incubator causes condensation to form on the shells. That moisture creates a perfect environment for bacteria and can clog the shell’s pores. To prevent this, let your eggs sit at room temperature for about two hours before placing them in the incubator. Spread them out on a towel or egg tray in a clean, draft-free area and let them warm gradually.
Once the eggs have reached room temperature and the surfaces are completely dry, place them in the incubator with the wide end slightly elevated or, if using automatic turners, follow the turner’s orientation guide. Mark each egg with a pencil (not a marker, which can leach through the shell) on two opposite sides so you can confirm turning is happening correctly in the days ahead. From this point on, the incubator takes over, but the work you did in selection, cleaning, storage, and preparation has already set the stage for a successful hatch.