Hey There!

Monitoring Egg Weight Loss for Accurate Incubation Humidity

Eggs are porous, which means they naturally lose moisture during incubation. As moisture escapes, the air sac inside the egg expands, and the egg's weight decreases. Most people monitor humidity inside the incubator to control this moisture loss, which should result in proper weight loss. However, egg porosity can vary depending on factors like size, age, and seasonal changes—making humidity alone an unreliable guide.

At Spring Hollow Acres, we prefer a more precise method: monitoring egg weight loss directly. This approach helps set the correct humidity for your incubator, especially when dealing with rare or expensive eggs, or if you're having trouble achieving good hatch rates.

​

The Basics of Egg Moisture Loss

After an egg is laid, it slowly begins to lose moisture through the shell. As this happens:

• The inner membrane begins to shrink.

• The air sac at the wide end of the egg increases in size.

• The overall weight of the egg decreases.

Inside the incubator, humidity levels determine how fast this evaporation occurs:

• High Humidity = slower evaporation and less weight loss

• Low Humidity = faster evaporation and more weight loss

For a successful hatch, moisture must evaporate at the right rate throughout incubation. If humidity is too low, chicks may become shrink-wrapped inside the shell, making hatching difficult. If it’s too high, chicks can become oversized or suffer from issues like mushy chick disease due to an underdeveloped air sac.

​

Why Monitor Egg Weight?

Instead of guessing if your incubator’s humidity is right, you can track egg weight to ensure the proper amount of moisture is being lost.

​

Ideal Weight Loss:

Poultry and waterfowl eggs should lose 11–13% of their weight from the start of incubation to the day turning stops (typically Day 18 for chickens).

You might see higher percentages quoted online, but those usually include the final few days when the chick starts to breathe internally. At that stage, weight loss naturally accelerates—sometimes by another 5%—so it's best to stop adjusting for weight loss after Day 18.

​

How to Monitor Egg Weight Loss Step-by-Step

You’ll need digital scales or a kitchen scale and a simple spreadsheet.

1. Set Up Your Incubator
   Set the temperature to 99.5°F and the humidity to 45–50%. Let it stabilize for a few hours.

2. Let Eggs Rest
   If your eggs were shipped, let them rest for 24 hours at room temperature, pointed-end down.

3. Weigh and Record
   Weigh the eggs as a group or individually (if your scale is precise), and record the starting weight.

4. Log the Data
   Enter the Day 1 weight and number of eggs into a spreadsheet. Continue weighing every day or every other day at the same time for consistency.

5. Adjust as Needed
   Compare your actual weight loss to the ideal curve (you can graph this in your spreadsheet). If weight loss is too fast, increase humidity slightly; if it’s too slow, lower it a bit.

6. Candle on Day 7
   Check for development. Remove any clear eggs and update your spreadsheet to reflect the new total and weight.

7. Monitor Until Lockdown
   Continue tracking weight and adjusting humidity until Day 18. Then stop turning the eggs and prepare for lockdown.

8. Lockdown (Days 19–21)
   Raise humidity to at least 60% and do not open the incubator. If your egg weights were close to target, you should have a smooth hatch.

Results You Can Expect

Books suggest you can improve hatch rates by around 10% with this method. In practice, we’ve seen people go from 20% success rates to over 80% just by dialing in humidity based on egg weight loss.