Humidity is one of the most
important factors determining your hatch rate, but, contrary to popular
belief, high humidity is more troublesome
than low humidity during most of the incubation period. During
hatch, of course, you want high humidity in the range of 65% or more so
that the chicks won't get stuck in the shell, but the goal is 40 to 50%
for the first 19 days.
In order to hatch
correctly, a chicken egg should lose 13% of its weight during
incubation, and that weight is lost in the form of water evaporating
out of the egg. Over time, the air pocket in the egg will get
larger as water evaporates out, creating a safe spot for your chick to
breath in between around day 19 and the time the chick hatches.
If the humidity in your incubator is too high, then your chick won't
have the appropriate air pocket and will die soon before pipping.
There are a few
different ways to get the right humidity in your incubator. The
simplest is to follow the instructions and fill a certain number of
wells with water, but this is a very hit or miss approach --- humidity
in your incubator is determined by the humidity outside the incubator
as well as by the amount of water in the wells. We live in a very
damp climate, and I suspect that following the instructions last time
around is part of what resulted in such a low
The second method is to
pencil the size of the air pocket on the outside of each egg at
intervals while candling. A chart like the one shown here can be
used to see if the egg's air pocket is growing at the right
speed. However, this technique requires a lot of judgement calls,
and would be time consuming if you're hatching more than a few eggs.
Another easy method to
get the proper level of humidity is to buy a fancy incubator with a
humidity readout. Our new Brinsea
Octagon 20 incubator
will definitely help us in that regard, but there's a big difference
between 40 and 50% humidity and I'd like to know whether my eggs are
losing weight at the proper rate.
Which brings us to the final
method of determining egg weight loss --- weighing your eggs.
This is the method I've chosen, so I'll go over the specifics of the
calculations in a later post.
No matter which method
you choose, you should be aware that it's the average
humidity over time that's important to your eggs, not the humidity at
any given moment. So it's okay to let the incubator wells
completely dry out for a day if you need to in order to get the average
humidity down lower. In fact, some incubation experts practice
dry incubation where they seldom or never fill the wells at the bottom
of the incubator.
I plan to use a hybrid approach, adding water as needed to keep our
eggs' weight loss on track.
Our chicken waterer makes daily chores so easy
that you have plenty of time to learn incubation.
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After several rounds of
trial and error, I figured out the best way to incubate chicks.
You can read the blow
by blow experimentation here, or splurge
99 cents on my ebook
for the more refined solutions.