This is a great idea! I never thought of this. I will try this with my pekin's I am hatching out! Thanks so much!I think 40% humidity is fine for the majority of the incubation. Make sure you have a really good thermometer, because we lost a whole batch of chicks on year because are thermometer was said 2 degrees lower than it was, so we basically roasted them...At lock down (3 days before hatch, so the around the 25th day) you can let the temp. go down a little, and what I did to get the humidity up to 70% was put a sterilized scent free sponge in the incubator (on a paper towel) and then I had a straw sticking though the hole in the top of the 'bator with a paper funnel on top, so I would just pour water on the sponge (without having to raise the top and let out humidity and heat) until it was up to the right percentage. When it got down to say 65% I would add more water.
Hope that helps!!!