Re: Incubator and humidity
To find this out, I installed a high quality humidity sensor in the mid brood nest of a good strong hive. The surprising thing was that humidity would change quite a bit, along with the outside humidity. So the relative humidity (RH) in the hive was always between 50 and 80.
Thing with that, the outside RH could be higher than the in hive RH, because the inside hive temperature was higher. RH is a percentage of how much water air can hold at a given temperature. So the amount of water in the air needed to achieve 100% saturation at say, 70 degrees, is less than 100% at 80 degrees, because air at 80 degrees can hold more water at 100% saturation. RH is Relative Humidity to 100%, at any given temperature. (hope all that makes sense).
So to the practical application in the incubator, I imitated the in broodnest conditions, and allowed humidity to fluctuate between 50% and 80% RH, but generally held it mid range at 60% or 70% RH. This was possible even when outside humidity was up to 95% RH, because the temperature in the incubator was higher, giving a lower RH for the same amount of water in the air.
I experimented with higher and lower humidity. Running RH in the incubator at 95% RH, the queens emerged with distended abdomens. They actually looked like nice big queens, but it was really water, and after a few hours they would excrete and shrink. So I decided this was probably not good for them. Humidity under 50% RH had the reverse effect, the queens emerged shrunken, which is probably also not good for them.
So end of day, 60% to 70% RH seemed to be the ideal, and is also the main area that humidity sits in an actual hive brood nest.
As to air movement, yes. If there is no air movement, there can be warmer air near the top and I found that by placing high quality sensors around the incubator. Only very slight air movement is needed, I achieved it in my incubator with a computer fan.
To create humidity, it is easy to overdo it. So I had a glass of water in the bottom of the incubator, with a computer fan pointing at it. If humidity went under 50% RH the fan came on, humidity would climb a few points then the fan would go off. I started out using a pan of water, but the large surface area made humidity go too high even when the fan was not on. So I changed to a glass, and the small surface area meant humidity only went up noticeably when the fan pointed at it was on.
Other thing, beware cheap humidity sensors. I have trialed quite a few, and found that the majority are not accurate. It is also hard to verify if they are accurate or not. So my suggestion would be test your humidity sensor in an actual hive, upper mid brood nest. Let it run a few days to get an average, then put the sensor in your incubator and set it the same as whatever the hive was. Do not be afraid to experiment, queen cells tolerate quite a wide variance in humidity, unlike temperature, where the ideal range is fairly narrow.
Last edited by Oldtimer; 07-10-2018 at 05:21 PM.
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