I go by "feel" on this one.
I'll try to describe my method.
Incubation boxes are a plastic shoe box with plain perlite moistened with tap water till clumpy, not soupy.
I place the eggs on top of the perlite. Maybe make a dimple in the perlite deep enough to keep the eggs from rolling around.
I incubate them at @ 82-84 F.
I error to keep my eggs a little on the dry side. I have found that keeping them dryer than not discourages mold/fungus problems. Also, too much humidity seems to decrease the hatching rate. The eggs absorb too much water and I guess maybe the neonate's egg yoke is diluted or something. Anyway the babies have a higher rate of being still-born. Almost or fully developed and dead in the egg.
I water my egg boxes just like a potted plant. I pick up the container and check the weight. If it feels light, I put my finger in the perlite and check for condensation on the walls of the container. You want some condensation on the walls but not enough to drip. You want the perlite to be saturated but only just moist to the feel. Take a hand full of the perlite and squeeze it.
Proper moisture should just clump and barely crumble. If it doesn't clump at all... add water. If it drips...too much.
I check my eggs every couple of days and wipe their bottoms free of any moisture build up.
I do want to point out again that I use clorinated water specifically for incubation as this seems to inhibit mold and fungal problems.
It is best to keep just enough ambiant humidity to keep the eggs from dehydrating. As a fail-safe...if I have eggs that start to dimple because of dehydration (they also can dimple just before they hatch naturally), I bury the eggs in the perlite and place a thuroughly rung out moist paper towel over the top of the eggs and they usually plump up in a day or two.
Just don't have them sitting in water.
Good Luck!
