Humidity in Incubation
An important factor to check during incubation is humidity.Promoted by Brinsea
Humidity is often difficult to understand for beginners, mostly because there can be conflicting information when you research humidity online. If you have questions about humidity during incubation, then you’ve come to the right place.
Ensure that your incubator has reached temperature (99.5°F for chickens) before adding water or trying to change the humidity. Humidity is relative, which we will discuss later, so you may inadvertently add too much water if you start raising the humidity before the incubator is up to temperature.
The Purpose of Humidity
Egg shells are porous, meaning they will naturally lose weight through the course of incubation. If the humidity is set to the right percentage, then the eggs will lose the right amount of weight. Developing chicks need enough air and space to move around, which is why it is important to regulate humidity.
Eggs losing too much weight is due to low humidity. This makes the air space larger than it should be, so the chick will be smaller and weaker. Low humidity is usually less of an issue than high humidity, but it can cause chicks to die before they are able to hatch.
The inverse of low humidity is high humidity, which means the egg does not lose enough weight. The chick will be larger (and stronger), but this is not necessarily better. Large chicks take up too much space, so they may not have enough air when they pip. They can die after pipping from lack of air, or they may not have enough space to maneuver into hatching position.
Humidity does not need to be strictly regulated in the same way as temperature. Throughout the course of incubation, you want the humidity level to average a certain level, so high or low humidity can be corrected later on in the process.
The amount of water vapor in the air relative to the temperature is how humidity is measured. This is known as Relative Humidity, or RH%. Wet bulb is another way to measure humidity and these should not be confused. 90°F wet bulb temperature is 45% RH not 90% RH!
Relative Humidity or RH%
RH% represents the measurement of water vapor in the air compared to the maximum that could be absorbed at that temperature. That means 50% humidity at 70°F is different from 50% humidity at 90°F. Raising the temperature in the incubator without adding water will cause the RH% to drop and vice versa.
Weighing Your Eggs
If you don’t have a hygrometer, or if you don’t trust your hygrometer, you can weigh your eggs to ensure proper humidity. Beware of cheap hygrometers and remember most are calibrated to room temperature, not incubation temperature. Most bird eggs need to lose around 13% of their weight from the first day of incubation until the last. You can weigh your eggs every few days and graph the weight loss to make sure you’re on track and adjust as necessary.
Adjusting the Humidity
Raising or lowering the humidity depends on two things. The first is water surface area. Depth of water does not affect humidity (although deeper water takes longer to evaporate completely), it really depends on how much surface area there is. More surface area = higher humidity. The second factor is how much fresh air can get inside the incubator. It will be hard to achieve high humidity if too much fresh air can get in. Some incubators come equipped with a vent, which allows you some control over the humidity. Misting eggs is not an effective method of raising humidity. It will only last a very short time and can cause bacterial contamination. It is not recommended.
Incubators are not air-tight (eggs need to breathe!) so the humidity outside can influence the humidity inside. If you live in a dry or wet climate, if you have a dehumidifier or a humidifier, if you are running the A/C, etc., all these factors can influence the humidity inside your incubator.
Humidity During Hatching
Most birds require higher humidity at hatching. This helps them hatch, because the high humidity keeps the egg membrane from drying up and trapping the chick inside. Once the chicks start hatching it is very important to keep the incubator lid closed, otherwise the humidity could drop and the membrane will dry out.
Automatic Humidity Control
Some incubators come equipped with a humidity pump and internal hygrometer that make incubation a little less stressful. Similar to the temperature control, the user can adjust the humidity level on the incubator and the pump will take care of adding water as necessary.