Humidity level can have a big effect on the success of your hatch — your hatch rate. Start by following any instructions that came with your incubator, but keep records and improvise from there. The more you incubate and learn from your results, the better results you will be able to get.
Humidity levels for incubation
When hatching in a tabletop styrofoam incubator, I’ve found that I get the best results when I keep the humidity near 45% for the first 18 days of incubation. I’ve tried incubating at closer to 55% relative humidity, but far fewer eggs hatched.
On Day 18 or 19, when I remove the egg turner and set the eggs onto the wire mesh floor of the incubator to finish incubation, I increase humidity to around 55-65% based on the recommendations that came with the egg turner.
In short, I recommend:
- 45% relative humidity for days 1-18
- 55-65% relative humidity for days 19 until the eggs hatch
Now that’s based on the setup that I am using, my climate, chickens, etc. I don’t know if you will get the same results.
Keep incubation records, including humidity
What I recommend that you do is the same thing I did. Keep records.
Every day, write down the date, time, humidity and temperature. Write them down several times a day.
Try to keep temperature and humidity as constant as you can.
Keep records of how many eggs hatched. How many where fertile? How many weren’t?
For eggs that didn’t hatch, try to figure out why. Were they simply not fertile? Was there a nutritional deficiency? Was there something you could change with how you are incubating them that might make a difference?
Then make a change and incubate again. Keep records again.
Over time, you’ll learn what works best for you.