Oh ok! I had read in an article that one should never use cardboard, as it said it contains fungi or something.Buy a dozen eggs in the store.Cardboard cartons work best and are easy to cut down.
I suppose if it was very old that might be an issue but I can’t imagine fungi would grow on a refrigerated egg carton. Not sure if this is true or not but I’ve never had a problem anyway.
I just have calibrated thermometers in my incubators that I check daily to make sure that everything is correct.
