So what did I learn? After opening the incubator door (to top up water or check on the eggs) the internal temperature decreases several degrees – this is fine! Mother hens get up to feed, drink and poo. So if you put your hydrometer in the incubator, initially the humidity appears to go up – it’s more humid in the incubator than outside (usually!) and you’ve also let alot of warm air out so the whole ‘closed’ incubator system has been disrupted. As the temperature climbs back to the pre set temp, the humidity seems to climb too…but if you wait, you will find it hits a peak than starts to decrease again, as the heat stabilizes and the air flow in the machine returns to normal. It can take longer than 10 minutes for the ‘normal’ humidity to re-establish itself which is why just popping a hydrometer in the incubator and taking a reading and then panicking about it is not particularly helpful.
For example on the 5th Nov 2015 when I added water and put my Aqua Pro hydro/thermometer; the humidity peaked a few minutes after it went in at 80% but 5 or so minutes later is had gone down to 60%. This isn’t the first time I’ve observed this. While the IM 12 digital auto turn incubators temperature reading said 37.5C within 10 min after I had opened the incubator and added water, the Aqua Pro took considerably longer to get there and it did eventually, but it had to climb from 21.3C in the kitchen up to the 37.5C inside the machine. Interestingly as the temp on the Aqua Pro increased (with time) the humidity eventually stabilized to 53%… comfortably in the range it should be for the first 18 days of incubating.
Aqua Pro Thermo/Hygrometer (No longer in stock)
Had I not taken the time to allow the system to stabilize I would not have realized that it was my adjustment/disruption of the system that was effecting the results. The moral of the story – if you want to use external measuring devices inside the incubator, leave them in there long enough to get a true reading 20/30 mins not 5 seconds!
Side note to the story, regardless of my fussing we hatched all 9 eggs – technically. In reality 8 of them got themselves out and are thriving and my 9th egg/chicken ‘Caesar’ who had an assisted birth is still alive (26th Nov). Also worthy of note is that the after I left the hydrometer in for its 30mins, the readings were a perfect 37.5C and 53% humidity. So Jeff scores the final point – when he told me I didn’t need to use external measuring device!