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PostPosted: Sat Aug 08, 2009 3:11 am 
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Hatchling
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Hey everyone.Im new to the forum and need some advice. I hope ive posted my question in the correct section!
I recently woke up one morning and decided to made a homemade incubator to show my children how chickens were born.
Im struggling with keeping the humidity, and can only manage about 30/35%! The temperature is stable at 100 F. I placed the chicken eggs in there on Tuesday morning this week. Ive turned them 3 times daily. I have 2 shallow containers with water and a rag in for added moisture.
Heres the build pics:

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Can anyone advise me on how to increase humidity? Are my eggs likely to be damaged from lack of humidity? Are they likely to hatch?

Many thanks in advance.

Rob.


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PostPosted: Sat Aug 08, 2009 8:45 am 
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Champion Bird
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Hi Rob,
Well done on the build it looks great

Humidity, well it depends on
a. how accurate the hygrometer is really reading.
b. How many ventilation holes you have, the mores holes means more air is exchanged and this will reduce the humidity, plus loose fitted doors and lids will let warm air escape.
c. Did you seal the MDF? MDF is quite good at drawing any moisture from the air, it will swell and warp and can also go mouldy.
d. What is the normal humidity like in your part of the UK at the moment, if it is quite dry in can be a battle to get the air in side the incubator moister.

Can you also explain what you have used as a thermostat? It looks like a dimmer control

Regards
Trev

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PostPosted: Sat Aug 08, 2009 8:47 am 
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There is a few issues to think about, but here's some background info about humidity.

The developing egg needs a consistent temperature, turning and appropriate humidity. The egg can tolerate fluctuations from the optimum relative humidity level to a wider degree than with the temperature, as the developing embryo does have some control over its water metabolism.

From the moment it is laid, the egg loses water by evaporation through the shell pores. At the moment of laying there is no actual air space, but as the egg contents contract slightly on cooling, the air space starts to form. The rate of water loss is determined by the temperature, the humidity, and the air flow round the egg. During incubation the rate of evaporation must be controlled. The size of the air cell is a good guide, but weighing the eggs is better. An egg must lose at least 11% of its initial weight in order to hatch. 13% is usually regarded as ideal. Part of this weight loss is evaporation. The optimum for incubation is said to be about 50-60% RH. Humidity can be increased in the incubator by increasing the surface area of the water. If you put a fan in your incubator, increasing the air flow over the surface of the water can also help. I also find putting the water containers closer to the heat source can help. Getting the humidity up in a still air machine can be a bit harder, and if you open the lid it takes a bit longer to recover.

As eggs can hatch in a range of humidity readings, I calibrate your hygrometer, do what you can to increase it if necessary, then run a batch of eggs to see what your rate of evaporation rate is. That's the best guide. The rate of loss is fairly rapid to start with, settles down to a plateau, then towards the end, speeds up again.

This might be too much information, but perhaps others are also interested. This Chart shows the range of acceptable weight loss over the incubation period and is taken from Anderson Brown's 'The Incubation Book'. He gives a tolerance of 3% either side of optimal.
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This is a guide if you are looking at the air cell:
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Instructions for calibrating your hygrometer are here:
viewtopic.php?f=6&t=7970593

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PostPosted: Sat Aug 08, 2009 7:34 pm 
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Proud Rooster
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is that a heater in the background.... would it be on?

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PostPosted: Sun Aug 09, 2009 8:41 am 
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Hi SillyM,
The post author is in the UK, its summer still over there so I wouldnt think the heater would be on. (Although we know that the English summers are not really summer)


Chicken, I have gone to the extremes of weighing eggs thru the whole incubation process and plotting the weight loss in excel, a very interesting exercise and learnt a fair bit from it.

Regards
Trev

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PostPosted: Sat Aug 15, 2009 3:46 pm 
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Did you record and analyse your results Trev? That would be interesting to see.


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PostPosted: Sat Aug 15, 2009 8:38 pm 
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Hi Chicken07,
It was an interesting exercise.
My wife designed a spreadsheet that graphed the weights of the eggs as an average for the batch against the min and max desirable weight loss.

It was a bit tedious as it involved weighing each egg seperatly and recording its weight in the spreadsheet at initial setting and then every 3 days untill hatch. If an egg was removed due to it being clear or early mortality you needed to zero the weights for that egg.

We used this method for the first 2 hatches with our home made bators to get an idea of how the bator performed humidity wise.

Cheers
Trev

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PostPosted: Sat Aug 15, 2009 10:34 pm 
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Trev, I can see why that would be a bit tedious. Still an interesting project though. I might give it a go soon just for interest's sake. An Excel spreadsheet is a good idea. That sounds like an easy way to remove eggs from the data set that don't make it. Thanks for the tip.

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PostPosted: Sun Aug 16, 2009 12:52 am 
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Showy Hen
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Hi,
Trev has a clean copy of that spreadsheet if you would like it please let us know.
Cheers,
Carmen


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PostPosted: Sun Aug 16, 2009 9:14 am 
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Thanks Carmen. I'll pm you.

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